{"id":1056,"date":"2014-05-01T01:13:35","date_gmt":"2014-05-01T01:13:35","guid":{"rendered":"http:\/\/phosdev.com\/todaysveterinarypractice\/?p=1056"},"modified":"2022-02-16T16:06:12","modified_gmt":"2022-02-16T16:06:12","slug":"lymph-node-cytology-what-should-should-not-be-there","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/cytology\/lymph-node-cytology-what-should-should-not-be-there\/","title":{"rendered":"Lymph Node Cytology: What Should &amp; Should Not Be There"},"content":{"rendered":"<p><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2016\/06\/T1405F01.pdf\"><img decoding=\"async\" class=\"alignnone size-full wp-image-9886\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2011\/07\/pdf_button.png\" alt=\"pdf_button\" width=\"110\" height=\"27\" \/><\/a><\/p>\n<hr \/>\n<p><em>Kim A. Selting, DVM, MS, Diplomate ACVIM (Oncology) &amp; ACVR (Radiation Oncology)<\/em><\/p>\n<p><em>University of Missouri<\/em><\/p>\n<p>Lymph node cytology results can strongly influence treatment and outcome for cancer patients. In this article, Dr. Selting discusses the necessary steps for identifying and aspirating the appropriate lymph nodes and for evaluating the cytologic results.<\/p>\n<hr \/>\n<p><span class=\"garamond-9-3-adjusted-for-article\">At the time of cancer diagnosis, the clinician\u2019s first task is to determine disease extent within the body, that is, to <\/span><em><span class=\"garamon-italics\">stage<\/span><\/em><span class=\"garamond-9-3-adjusted-for-article\"> the cancer.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Stage<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> describes the extent of the tumor, lymph node involvement, and spread of disease, measuring the scope of metastasis. <\/span><strong><span class=\"garamond-bold\">Grade<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> describes the appearance of the cells upon histopathology. Higher <\/span><em><span class=\"garamon-italics\">grade<\/span><\/em><span class=\"garamond-9-3-adjusted-for-article\"> tumors are more likely to present at a higher <\/span><em><span class=\"garamon-italics\">stage<\/span><\/em><span class=\"garamond-9-3-adjusted-for-article\">. Staging is performed by the clinician, whereas grading is performed by the pathologist.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">With practice, enough information can be gained from lymph node cytology to allow the general practitioner to begin a dialogue with pet owners about concern for metastatic cancer and its impact on prognosis.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">This article reviews normal and abnormal lymph node cytology in both solid and round\/discrete cell (hemolymphatic) tumors from the perspective of an oncologist.<\/span><\/p>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">ROUTES OF METASTASIS<\/span><\/h2>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Cancer can metastasize via lymphatics or blood vessels (hematogenously):<\/span><\/p>\n<ul>\n<li><strong><span class=\"garamond-bold\">Mesenchymal tumors (sarcomas) predominantly metastasize via blood vessels<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">, but can occasionally travel by lymphatics, which is typically a sign of more aggressive disease\u2014one that metastasizes more readily, resulting in shorter survival times.<\/span><\/li>\n<li><strong><span class=\"garamond-bold\">Epithelial (carcinomas) and round\/discrete cell tumors metastasize via lymphatics<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> more often than mesenchymal tumors.<\/span><\/li>\n<\/ul>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Regardless of tumor type, regional lymph node cytology should be included in the first wave of diagnostics for most cancers.<\/span><\/p>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">LYMPH NODES TO SAMPLE<\/span><\/h2>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">While metastasis to an unexpected lymph node is always possible, the important lymph nodes to aspirate at time of staging are:<\/span><\/p>\n<ul>\n<li><span class=\"garamond-9-3-adjusted-for-article\">The primary <\/span><strong><span class=\"garamond-bold\">draining lymph node<\/span><\/strong><\/li>\n<li><span class=\"garamond-9-3-adjusted-for-article\">Any <\/span><strong><span class=\"garamond-bold\">enlarged lymph nodes<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> (even if distant from the primary tumor).<\/span><\/li>\n<\/ul>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">For several tumors, including melanoma and mast cell tumor, metastasis can be identified even if lymph nodes are of normal size.<sup>1<\/sup> In addition to screening for metastasis of solid tumors, lymphoma is often easily diagnosed using lymph node aspiration and cytology.<\/span><\/p>\n<div class=\"orange-box\">\n<p class=\"indent-125\">In one large case series of dogs with osteosarcoma, incidence of lymph node metastasis was only 4%, but the median disease-free interval was only 48 days in dogs with &#8220;positive&#8221; lymph nodes compared with 238 days for dogs with unaffected lymph nodes.<sup><span style=\"font-size: small\">2<\/span><\/sup><\/p>\n<\/div>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">FINE-NEEDLE ASPIRATION<\/span><\/h2>\n<h3 class=\"left-justified\"><span class=\"font_purple\">Location Considerations<\/span><\/h3>\n<p class=\"left-justified\"><strong><span class=\"garamond-bold\">When evaluating metastatic solid tumors<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">, the primary draining lymph node that should be sampled depends upon location (eg, popliteal node for a hind foot digital tumor). Tumors located in areas of the body where lymphatic drainage is not clear, such as on the lateral thorax, can be challenging. In this situation, the nearest major lymph node should be aspirated if it can be isolated, though at times this is not possible and lymph nodes are noted as within normal limits without cytologic interpretation.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">When diagnosing lymphoma<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">, the popliteal lymph nodes are the most accessible lymph nodes, followed by the pre-scapular nodes. Mandibular lymph nodes should be avoided if other nodes are enlarged, because reactive lymphoid cells (due to changes in the ears or mouth) may cloud a diagnosis of lymphoma. However, if the mandibular nodes are the only enlarged lymph nodes, they should be aspirated. A cytologic diagnosis of reactive or equivocal lymph node should be interpreted with caution: if lymphoma is suspected, further testing, such as biopsy, should be pursued if suspicion is high.<\/span><\/p>\n<div class=\"orange-box\">\n<h2 class=\"indent-125\"><span class=\"bluboldheader\">Findings That Complicate Diagnosis<\/span><\/h2>\n<h3 class=\"indent-125\"><span class=\"purple\">Reactive Lymph Nodes<\/span><\/h3>\n<p class=\"indent-125\">Reactive lymph nodes are characterized by increased numbers of plasma cells, notable due to their deeply basophilic cytoplasm and perinuclear clear zone.<\/p>\n<ul>\n<li>Increased numbers of lymphoblasts are often seen in reactive lymph nodes, but they should not total more than 50% of the lymphoid population.<\/li>\n<li>Increased numbers of neutrophils are also seen, and other inflammatory cells, such as eosinophils may also be present.<\/li>\n<\/ul>\n<h3><span class=\"purple\">Inflammatory Cells<\/span><\/h3>\n<p>When inflammatory cells are present, they can sometimes obscure metastatic cells or make cytologic changes difficult to interpret. The presence of mast cells in a lymph node near a mast cell tumor can be especially challenging. While some mast cells may represent cytokine signaling and chemotaxis attracting normal mast cells, a high proportion as well as clustering of mast cells may represent true metastatic disease.<\/p>\n<h3><span class=\"purple\">Infectious Organisms<\/span><\/h3>\n<p>Other findings that do not belong in lymph nodes include infectious organisms, which may be seen against a background of reactive lymphocytes and inflammatory cells. Fungal and bacterial causes of lymphadenopathy can stimulate increased numbers of macrophages and neutrophils.<\/p>\n<\/div>\n<h3 class=\"indent-125\"><span class=\"font_purple\">Isolation of Node<\/span><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">When isolating a lymph node:<\/span><\/p>\n<ol>\n<li class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Place the forefingers in an anatomic location just beyond the node.<\/span><\/li>\n<li class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Use the thumb to isolate and steady the node.<\/span><\/li>\n<\/ol>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">For example, to isolate the prescapular\/superficial cervical node:<\/span><\/p>\n<ol>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Place the fingers in, or just above, the thoracic inlet.<\/span><\/li>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Sweep the thumb down the front of the shoulder where the supraspinatus muscles meet the neck muscles.<\/span><\/li>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">The gesture above will guide the node between the thumb and forefinger.<\/span><\/li>\n<\/ol>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">While each practitioner will develop their own feel for lymph node palpation, this technique may help isolate the deeper and more elusive lymph nodes.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Normal sized lymph nodes can sometimes be difficult to palpate and properly aspirate, especially in overweight or heavily muscled (eg, Staffordshire terrier, some Labrador retriever) dogs. To increase the chance of success, before isolating the node itself:<\/span><\/p>\n<ol>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Use a reference point as described above.<\/span><\/li>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Make a mental note of normal structures that are palpated near the node.<\/span><\/li>\n<\/ol>\n<h3 class=\"tabs-and-bullets\"><span class=\"font_purple\">Fine-Needle Aspiration<\/span><\/h3>\n<ol>\n<li class=\"tabs-and-bullets\"><span class=\"garamond-9-3-adjusted-for-article\">Use a needle without a syringe attached; any gauge is acceptable, but my preference is to use a 22-gauge needle to avoid discomfort.<\/span><\/li>\n<li class=\"tabs-and-bullets\"><span class=\"garamond-9-3-adjusted-for-article\">Once a node is trapped between thumb and forefinger, introduce the needle.<\/span><\/li>\n<li class=\"tabs-and-bullets\"><span class=\"garamond-9-3-adjusted-for-article\">Redirect the needle by moving it in and out through the node several times, until\u2014when looking into the needle hub\u2014a tiny bleb is apparent within the needle\u2019s inner circumference; this avoids unnecessary hemodilution.<\/span><\/li>\n<\/ol>\n<h3><strong><span class=\"font_purple\">Slide Preparation<\/span><\/strong><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">The following technique provides high-quality diagnostic slides for needle aspiration cytology:<\/span><\/p>\n<ol>\n<li class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Attach an air-filled syringe to the needle and expel only \u00bd drop from the needle onto each of 2 to 3 slides, which keeps each slide\u2019s sample the right consistency, avoiding preparations that are too thick (<\/span><strong><span class=\"garamond-bold\">Figure 1A<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/li>\n<li class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Gently lay a clean slide crosswise on the droplet, allowing it to break the surface tension (<\/span><strong><span class=\"garamond-bold\">Figure 1B<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/li>\n<li class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">While holding the slide on both ends with the free hand, gently pull the spreading slide across the aspirate slide, which allows good smearing of the droplet (<\/span><strong><span class=\"garamond-bold\">Figure 1C and 1D<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">). This technique avoids applying too much pressure on the sample and traumatizing the cells.<\/span><\/li>\n<\/ol>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\"><em><strong>Note:<\/strong><\/em> If you stain a slide in-house using rapid fixation stains in preparation for laboratory evaluation, always send at least one unstained slide, which allows the clinical pathologist to apply his or her own stain.<\/span><\/p>\n<p class=\"indent-125\"><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.43-AM.png\"><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone size-full wp-image-4730\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.43-AM.png\" alt=\"Screen Shot 2015-06-18 at 11.05.43 AM\" width=\"545\" height=\"483\" srcset=\"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.43-AM.png 545w, https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.43-AM-300x266.png 300w\" sizes=\"(max-width: 545px) 100vw, 545px\" \/><\/a><\/p>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">CYTOLOGIC EVALUATION<br \/>\n<\/span><\/h2>\n<h3 class=\"left-justified\"><strong><span class=\"font_purple\">Lymphocyte Size<\/span><\/strong><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Lymph nodes are predominantly comprised of small, mature lymphocytes (80%\u201390%). Lymphoid cells typically have high nuclear to cytoplasmic ratios.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Size is important when determining whether the lymphoid population is of concern. Cell size is typically compared to a red blood cell (RBC), but neutrophils are less likely to fold and pile up, and are slightly larger than RBCs.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Therefore, if possible, the nucleus should be compared to a RBC, and the whole cell to a neutrophil, if any are present (<\/span><strong><span class=\"garamond-bold\">Table 1<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/p>\n<table border=\"1\" width=\"100%\" cellspacing=\"0\" cellpadding=\"3\">\n<tbody>\n<tr>\n<td class=\"font_purple\" style=\"text-align: left\" colspan=\"3\" align=\"center\"><strong>TABLE\u00a01. Lymphocyte Size &amp; Appearance<\/strong><\/td>\n<\/tr>\n<tr class=\"aquabold\">\n<td>Type<\/td>\n<td>Size<\/td>\n<td>Appearance<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><em>Lymphocytes: <\/em><br \/>\n<strong>Small Mature<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Same size or smaller than neutrophil or RBC<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Dense chromatin in nucleus (more deeply basophilic appearance)<br \/>\n\u2022 High nuclear:cytoplasmic ratio (very little cytoplasm)<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><em>Lymphocytes:<\/em><br \/>\n<strong>Intermediate<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Similar to, or only slightly larger than, neutrophil<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Interpret in light of total cell population (<strong>Table 3<\/strong>)<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><em>Lymphoblasts:<\/em><br \/>\n<strong>Large Immature<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Larger than neutrophil or RBC<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Looser chromatin in nucleus (lighter blue appearance)<br \/>\n\u2022 Lower nuclear:cytoplasmic ratio (more cytoplasm)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3 class=\"indent-125\"><span class=\"font_purple\">Categories of Neoplasms<\/span><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">After evaluating lymphocyte cell size, the next step in successful cytologic evaluation is to determine whether any other types of cells that represent metastasis to the node are present. If present, these cells can be categorized as mesenchymal, epithelial, or round\/discrete. In addition, uncommon categories, such as neuroendocrine or histiocytic, may be relevant.<\/span><\/p>\n<h3 class=\"left-justified\"><span class=\"font_purple\">Criteria of Malignancy<\/span><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Finding cells where they do not belong, such as the presence of epithelial cells in a lymph node, is a sign of neoplasia.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Malignant cells<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> are bizarre, and may not immediately resemble their cell of origin. While atypia can be seen in diseased tissue, the presence of cytologic changes outlined in <\/span><strong><span class=\"garamond-bold\">Table 2<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">, combined with lack of inflammation, is a strong indication of malignancy:<\/span><\/p>\n<ul>\n<li class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">When inflammation is prominent, it can be difficult to commit to a diagnosis of cancer.<\/span><\/li>\n<li><span class=\"garamond-9-3-adjusted-for-article\">However, very bizarre cells support a diagnosis of malignancy even if some inflammation is present.<\/span><\/li>\n<\/ul>\n<table border=\"1\" width=\"100%\" cellspacing=\"0\" cellpadding=\"3\">\n<tbody>\n<tr>\n<td class=\"font_purple\" style=\"text-align: left\" colspan=\"3\" align=\"center\"><strong>TABLE\u00a02. Malignancy Criteria<\/strong><\/td>\n<\/tr>\n<tr>\n<td colspan=\"3\" bgcolor=\"#d8efe1\">\n<ul>\n<li>Mitotic figures, especially if bizarre, with haphazardly arranged, instead of orderly, chromatin<\/li>\n<li>Multiple nuclei, especially if an odd number<\/li>\n<li>Multiple nucleoli, especially if they vary in size<\/li>\n<li>Anisocytosis<\/li>\n<li>Anisokaryosis<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong><span class=\"garamond-bold\">Fibroblasts<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can be misleading\u2014tumors can elicit a scirrhous response in which reactive fibroblasts are present among an atypical population, potentially creating the impression of a mesenchymal neoplasm, when the primary malignant process has a different origin, such as carcinoma or mast cell tumor.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Mitotic figures<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can be seen in both normal and reactive lymph nodes as part of the normal renewal of lymphocytes. Mitotic figures that are concerning include those:<\/span><\/p>\n<ul>\n<li><span class=\"garamond-9-3-adjusted-for-article\">Accompanied by cells that display other cytologic criteria of malignancy<\/span><\/li>\n<li><span class=\"garamond-9-3-adjusted-for-article\">With bizarre chromatin patterns, including polar asymmetry, distraction of chromatin to more than 2 poles, and chromatin lagging and bridging.<sup>3<\/sup><\/span><\/li>\n<\/ul>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">In some cases, a biopsy is needed to confirm the presence of a neoplasm, and it is often needed to confirm type of cancer.<\/span><\/p>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">DIAGNOSES BASED ON LYMPH NODE CYTOLOGY<\/span><\/h2>\n<h3 class=\"left-justified\"><span class=\"font_purple\">Lymphoma<\/span><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">The most common finding on fine-needle aspiration and cytology of lymph nodes that are enlarged due to lymphoma is a monomorphic population of lymphoblasts (<\/span><strong><span class=\"garamond-bold\">Figure 2<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">). Characteristics of lymphoma identified by lymph node cytology are listed in <\/span><strong><span class=\"garamond-bold\">Table 3<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">.<\/span><\/p>\n<p class=\"left-justified\"><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.59-AM.png\"><img decoding=\"async\" class=\"alignnone wp-image-4731\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.59-AM.png\" alt=\"Screen Shot 2015-06-18 at 11.05.59 AM\" width=\"517\" height=\"360\" srcset=\"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.59-AM.png 546w, https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Screen-Shot-2015-06-18-at-11.05.59-AM-300x209.png 300w\" sizes=\"(max-width: 517px) 100vw, 517px\" \/><\/a><\/p>\n<table border=\"1\" width=\"100%\" cellspacing=\"0\" cellpadding=\"3\">\n<tbody>\n<tr>\n<td class=\"font_purple\" style=\"text-align: left\" colspan=\"3\" align=\"center\"><strong>TABLE\u00a03. Lymphoma Characteristics Identified by Lymph Node Cytology<\/strong><\/td>\n<\/tr>\n<tr>\n<td colspan=\"3\" bgcolor=\"#d8efe1\">\n<ul>\n<li>All (or almost all) cells in the aspirate will be lymphoblasts characterized by:\n<ul>\n<li>High nuclear:cytoplasmic ratio<\/li>\n<li>Loose chromatin pattern<\/li>\n<li>Discrete cell pattern: Abundant cellular yield, round cells and nuclei, and no obvious clustering (although number\/close proximity of cells may initially resemble clustering)<\/li>\n<\/ul>\n<\/li>\n<li>Anisocytosis and anisokaryosis may be present<\/li>\n<li>The sample often lacks any indication of inflammation<\/li>\n<li>Monomorphic cells (roughly the same size and shape) that are intermediate or small in size should arouse suspicion of lymphoma\u2014a normal or reactive lymph node contains lymphocytes and lymphoblasts of many different sizes, though smaller in proportion to mature lymphocytes<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">Comparison to RBCs or neutrophils can help with size determination. It is tempting to suspect lymphoma when a large population of lymphoblasts is seen; however, use caution and spend some time evaluating all the cells\u2014there may be more small lymphocytes present than appreciated initially.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">If an enlarged lymph node is reactive, there should be a population of plasma cells and inflammatory cells, and more variety to the lymphoid population (<\/span><strong><span class=\"garamond-bold\">Figure 3<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Biopsy<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> may be needed to confirm the diagnosis if only lymphoid cells\u2014most of similar size (and intermediate or small)\u2014are seen; however, lymphoma should be strongly suspected. This is especially true when multiple peripheral nodes are enlarged and the dog is asymptomatic, because infectious causes of lymphadenopathy more often lead to clinical signs of illness.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Histopathology<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can identify marginal and T-zone lymphomas that are indolent; biopsy specimens should ideally include the entire node and should be sent to a pathologist with expertise in this area. These lymphomas may not require treatment; if treated, they have a lower response rate to treatment but longer survival times.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Flow cytometry<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can determine the immunophenotype of a labeled cell. Immunophenotype of lymphoma affects prognosis; median survival for T-cell lymphoma is typically one-half the median survival for B-cell lymphoma for a given chemotherapy protocol. Flow cytometry is performed on a needle aspirate sample suspended in a special medium.<\/span><\/p>\n<blockquote>\n<p class=\"indent-125\"><strong>When using flow cytometry<\/strong>, the laboratory that will be processing the sample should be contacted before sample collection, as special handling (suspending the aspirate in a specific medium, and overnight shipping on ice) is required.<\/p>\n<\/blockquote>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Immunohistochemistry<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> (biopsy samples) or <\/span><strong><span class=\"garamond-bold\">immunocytochemistry<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> (fine-needle aspirate samples) can also be used to determine immunophenotype.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">While knowledge of immunophenotype may provide an improved understanding of expected outcome, and while some clinicians favor certain protocols based on immunophenotype (some clinicians prefer alkylator-heavy protocols for T-cell lymphoma), it has never been shown that modifying the chemotherapy protocol based on knowledge of immunophenotype improves outcome, and multidrug (CHOP-based) protocols are still effective for all high-grade lymphomas.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">PCR for Antigen Receptor Rearrangement (PARR)<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can be performed on aspirate slides when a diagnosis of lymphoma is elusive. With this technique, DNA of the variable regions encoding the immunoglobulin and T-cell receptors is amplified.<\/span><\/p>\n<ul>\n<li><span class=\"garamond-9-3-adjusted-for-article\">In a normal immune system, there is great variety to protect the body from as many antigens as possible.<\/span><\/li>\n<li><span class=\"garamond-9-3-adjusted-for-article\">When a lymphocyte or lymphoblast undergoes a malignant transformation, then clonally expands, there is great redundancy in the lymphoid population of a sample.<\/span><\/li>\n<li><span class=\"garamond-9-3-adjusted-for-article\">In other words, all malignant lymphocytes are programmed to make the same receptor because they all came from the same progenitor; PARR detects this monotony.<\/span><\/li>\n<\/ul>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Thus, detection of monoclonal population of cells by PARR confirms the presence of neoplasia. False positive tests are rare, but may be seen with ehrlichiosis.<\/span><\/p>\n<h3 class=\"left-justified\"><span class=\"font_purple\">Solid Tumor Metastasis<\/span><\/h3>\n<p class=\"left-justified\"><span class=\"garamond-9-3-adjusted-for-article\">When lymph nodes are completely effaced with tumor cells, the diagnosis of metastatic neoplasia is often straightforward. However, in the absence of background lymphocytes, it can sometimes be difficult to determine with certainty whether the aspirated structure actually was a lymph node. In most cases, the sample contains small numbers of metastatic cells mixed with lymphocytes (<\/span><strong><span class=\"garamond-bold\">Table 4<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/p>\n<table border=\"1\" width=\"100%\" cellspacing=\"0\" cellpadding=\"3\">\n<tbody>\n<tr>\n<td class=\"font_purple\" style=\"text-align: left\" colspan=\"3\" align=\"center\"><strong>TABLE 4. Appearance of Metastatic Cells Found in Lymph Nodes<\/strong><\/td>\n<\/tr>\n<tr class=\"GreenAqua\">\n<td>METASTATIC CELLS<\/td>\n<td>APPEARANCE<\/td>\n<td>CELLS ORIGINATE FROM:<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><strong>Mesenchymal Cells<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Round to ovoid nuclei<br \/>\n\u2022 Indistinct cell borders<br \/>\n\u2022 Trailing\/wispy cytoplasm<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Sarcoma<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><strong>Epithelial Cells<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Round nuclei<br \/>\n\u2022 Abundant, angular cytoplasm<br \/>\n\u2022 Tend to occur in clusters or sheets*<br \/>\n\u2022 Background population of mostly small lymphocytes<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Carcinoma<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" bgcolor=\"#d8efe1\"><strong>Round Cells<\/strong><\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">\u2022 Round nuclei<br \/>\n\u2022 Cytoplasm of varying amounts<\/td>\n<td valign=\"top\" bgcolor=\"#d8efe1\">Histiocytoma<br \/>\nLymphosarcoma<br \/>\nMast cell tumor<br \/>\nMelanoma**<br \/>\nPlasmacytoma<br \/>\nTransmissable venereal tumor<\/td>\n<\/tr>\n<tr>\n<td class=\"font_purple\" style=\"text-align: left\" colspan=\"3\" align=\"center\">* These may be infrequent, requiring that the entire slide be carefully examined.<br \/>\n** Melanoma may occasionally be categorized differently, depending on the characteristics of individual tumors.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"left-justified\"><strong><span class=\"garamond-bold\">Diagnosis based on cytology<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> of a metastatic lymph node\u2014even before the primary tumor is located\u2014is not uncommon. One example is oral tumors: because owners do not routinely look inside their dogs\u2019 mouths, they may present the pet because a mass was noted in the mandibular region (<\/span><strong><span class=\"garamond-bold\">Figure 4<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">).<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Early metastasis can be challenging, because its presence can cause some degree of reactivity in the node (<\/span><strong><span class=\"garamond-bold\">Figure 5<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">) or, if metastasis to lymph nodes has occurred, in regions of the node that are not sampled by fine-needle aspiration.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Lymph node biopsy <\/span><span class=\"garamond-9-3-adjusted-for-article\">or<\/span><span class=\"garamond-bold\"> removal for histopathology<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> should be performed if there is concern for metastasis based on size or shape of a lymph node that cannot be confirmed on cytology.<\/span><\/p>\n<div id=\"attachment_8633\" style=\"width: 310px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-4.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-8633\" class=\"wp-image-8633 size-medium\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-4-300x221.png\" alt=\"lymph fig 4\" width=\"300\" height=\"221\" srcset=\"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-4-300x221.png 300w, https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-4.png 708w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><p id=\"caption-attachment-8633\" class=\"wp-caption-text\">Figure 4. Squamous cell carcinoma metastasis to a lymph node: the abundant population of small lymphocytes in the background confirms lymph node origin, but the large, angular epithelial cells with abundant cytoplasm do not belong in a lymph node under any circumstance; note the occasional lymphoblast and plasma cell. <em>Courtesy Dr. Natalie Hoepp<\/em><\/p><\/div>\n<div id=\"attachment_8634\" style=\"width: 310px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-5.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-8634\" class=\"wp-image-8634 size-medium\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-5-300x225.png\" alt=\"lymph fig 5\" width=\"300\" height=\"225\" srcset=\"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-5-300x225.png 300w, https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-fig-5.png 697w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><p id=\"caption-attachment-8634\" class=\"wp-caption-text\">Figure 5. View (2\u00d7) of a sectioned histologic specimen of a lymph node showing the limitations of needle aspirates: On the left side of the image, the node is effaced with a neoplastic cell population, but the right side of the specimen shows a reactive lymph node population. Needle aspiration can miss a neoplastic population, and histopathology is recommended if there is clinical concern. <em>Courtesy Dr. Tamara Hancock<\/em><\/p><\/div>\n<p><strong><span class=\"garamond-bold\">Lymph nodes draining in the region of a mast cell tumor<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> can be particularly troubling, because some mast cells are normally found in reactive lymph nodes. When reactive mast cells are recruited to local lymph nodes by cytokines produced by the mast cell tumor (ie, nonmetastatic mast cells), they are expected to infiltrate the node individually. In addition to metastatic mast cells found in lymph nodes meeting cytologic criteria of malignancy (<\/span><strong><span class=\"garamond-bold\">Table 2<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">), clustering of these cells (into aggregates) can also signify metastatic disease.<sup>4<\/sup> When in doubt, the lymph node should be surgically removed and submitted for histopathology, perhaps at the time of initial mast cell surgery.<\/span><\/p>\n<p class=\"indent-125\"><strong><span class=\"garamond-bold\">Lymph node involvement in mast cell tumors<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\"> impacts both treatment and prognosis of these tumors. Locoregional treatment of a mast cell tumor with surgery, with or without radiation therapy to include a local lymph node, can be very successful unless metastasis has spread beyond the regional lymph node.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Melanocytes, characterized by their granules, should not be present in regional lymph nodes and typically represent metastatic disease (<\/span><strong><span class=\"garamond-bold\">Figure 6<\/span><\/strong><span class=\"garamond-9-3-adjusted-for-article\">). However, lymph nodes can contain regional melanophages\u2014large round cells with abundant, vacuolated cytoplasm\u2014and this may not represent metastatic disease.<\/span><\/p>\n<div id=\"attachment_8630\" style=\"width: 310px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-node-fig-6-a.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-8630\" class=\"wp-image-8630 size-medium\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-node-fig-6-a-300x223.png\" alt=\"lymph node fig 6 a\" width=\"300\" height=\"223\" srcset=\"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-node-fig-6-a-300x223.png 300w, https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/lymph-node-fig-6-a.png 703w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><p id=\"caption-attachment-8630\" class=\"wp-caption-text\">Figure 6. Melanophages, containing abundant dark pigment, can be seen in areas of chronic inflammation and other nonneoplastic pathology in draining lymph nodes. However, the more lightly granulated cell on the lower right (arrows) is a melanocyte, which should not be present in a lymph node and, therefore, is consistent with lymph node metastasis. <em>Courtesy Dr. Erin Burton<\/em><\/p><\/div>\n<h2 class=\"left-justified\"><span class=\"bluboldheader\">IN SUMMARY<\/span><\/h2>\n<p class=\"indent-125\"><span class=\"garamond-9-3-adjusted-for-article\">Lymph node cytology can be performed quickly, as a minimally invasive procedure, and results can strongly influence treatment and outcome for cancer patients. Like any other skill, evaluation of cytology from a lymph node takes time and practice.<\/span><\/p>\n<p class=\"indent-125\"><span class=\"helvetica-9-pt\">PARR = PCR for antigen receptor rearrangement; RBC = red blood cell<\/span><\/p>\n<h3 class=\"indent-125\">References<\/h3>\n<ol>\n<li class=\"indent-125\">Williams LE, Packer RA. Association between lymph node size and metastasis in dogs with oral malignant melanoma: 100 cases (1987-2001). <em><span class=\"refersitalics\">JAVMA<\/span> <\/em>2003; 222(9):1234-1236.<\/li>\n<li class=\"indent-125\">Hillers KR, Dernell WS, Lafferty MH, et al. Incidence and prognostic importance of lymph node metastases in dogs with appendicular osteosarcoma: 228 cases (1986-2003). <em><span class=\"refersitalics\">JAVMA<\/span> <\/em>2005; 226(8):1364-1367.<\/li>\n<li class=\"indent-125\">Tvedten H. Atypical mitoses: Morphology and classification. <em><span class=\"refersitalics\">Vet Clin Pathol<\/span> <\/em>2009; 38(4):418-420.<\/li>\n<li class=\"indent-125\">Krick EL, Billings AP, Shofer FS, et al. Cytological lymph node evaluation in dogs with mast cell tumours: Association with grade and survival. <em><span class=\"refersitalics\">Vet Comp<\/span> <span class=\"refersitalics\">Oncol<\/span> <\/em>2009; 7(2):130-138.<\/li>\n<\/ol>\n<p><span class=\"author-bio\"><strong><a href=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Kim-A.-Selting.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-8625\" src=\"https:\/\/todaysveterinarypractice.com\/wp-content\/uploads\/sites\/4\/2014\/05\/Kim-A.-Selting.png\" alt=\"Kim A. Selting\" width=\"100\" height=\"115\" \/><\/a>Kim A. Selting<\/strong>, DVM, MS, Diplomate ACVIM (Oncology) &amp; ACVR (Radiation Oncology), is an associate teaching professor at University of Missouri. She developed an international searchable database to promote veterinary cancer clinical trials at vetcancertrials.org. She completed her DVM and specialty training at Colorado State University, with a rotating internship at the Animal Medical Center in New York City.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Kim A.<\/p>\n","protected":false},"author":1,"featured_media":3048,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"iawp_total_views":5786,"footnotes":""},"categories":[366],"tags":[13],"class_list":["post-1056","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-may-june-2014","tag-peer-reviewed","column-features","clinical_topics-cytology","clinical_topics-oncology"],"acf":{"hide_sidebar":false,"hide_sidebar_ad":false,"hide_all_ads":false},"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v24.7 (Yoast SEO v27.3) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Lymph Node Cytology: What Should &amp; Should Not Be There<\/title>\n<meta name=\"description\" content=\"In this article, Dr. Selting discusses steps for identifying and aspirating the appropriate lymph nodes and for evaluating the cytologic results.\" \/>\n<meta name=\"robots\" content=\"noindex, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Lymph Node Cytology: What Should &amp; 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