1 When should a lymph node be aspirated for cytology?

Lymph node aspiration is useful whenever one or multiple lymph nodes are enlarged. Aspiration of a nonenlarged node is difficult and usually results in aspiration of perinodal fat with little or no lymphoid tissue present. However, aspiration of a nonenlarged node is sometimes attempted to check for metastatic neoplasia.

2 List some diagnoses made from lymph node aspirates.

3 What is the cytologic appearance of an aspirate from a normal lymph node?

Aspirates from normal lymph nodes consist of 75% to 95% (usually about 90%) small mature lymphocytes (Figure 43-1). Small lymphocytes are slightly larger than the size of a canine red blood cell (RBC) and about 1.5 to 2 times the size of a feline RBC. They have a dark staining, roundish nucleus with densely aggregated chromatin and no visible nucleoli. Small lymphocytes have a scanty amount of clear to light-blue cytoplasm that is generally visible only on one side of the nucleus (not visible all the way around nucleus). Other cell types are present in low numbers and may include lymphoblasts, prolymphocytes, plasma cells, macrophages, neutrophils, and mast cells. Lymphoglandular bodies, bare nuclei, and strands of nuclear chromatin are often present as well.

Figure 43-1 Normal lymph node. Lymph node aspirate from a dog showing high numbers of small lymphocytes and one lymphoblast (arrow). (Wright’s stain; 250×.)

4 What are lymphoglandular bodies?

Lymphoglandular bodies are cytoplasmic fragments from lymphoid cells. This is a normal finding in all lymphoid tissues. The main concern is not to confuse lymphoglandular bodies with an organism or cell.

5 What is the cytologic appearance of a hyperplastic lymph node, and how does it differ from a normal lymph node?

Cytologically, no clear line of separation exists between a normal and a hyperplastic lymph node. Both may look identical to the other, and the cytologic evaluation of the lymph node aspirate is reported as “hyperplastic” because the node is enlarged.

6 What is a reactive lymph node, and how does it differ from a hyperplastic lymph node?

Often the term “reactive” is used instead of “hyperplastic” when there are mildly increased numbers of inflammatory cells (macrophages, neutrophils, eosinophils), lymphoblasts, or prolymphocytes. Plasma cell numbers may be mildly to greatly increased.

7 What is a Mott cell?

A Mott cell is a plasma cell that has its cytoplasm filled with roundish vacuoles that stain clear to light blue (Figure 43-2). These vacuoles, termed Russell bodies, are packets of immunoglobulin.

Figure 43-2 Mott cell. Lymph node aspirate showing many small lymphocytes and plasma cells (arrows), a macrophage, and a Mott cell (double arrow). Many lymphoglandular bodies are present in the background of the smear. (Wright’s stain; 250×.)

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