Lymph node cytology (Proceedings)
Lymph node cytology
You should consider three major processes when evaluating cells from an enlarged lymph node: 1) Reactive lymph node 2) Lymphadenitis 3) Neoplasia- lymphoma or metastatic.
Enlarged lymph nodes tend to exfoliate well and often yield very thick aspirates. It is important to examine the thinner, more peripheral portions of the smear, as the thick, central regions often do not stain well. Regardless of aspiration or smear technique, lymphocytes tend to be fragile and many will rupture on the slide. These cells will appear as large, pale pink nuclei without any surrounding cytoplasm and should be disregarded. Numerous small, round basophilic structures about the size of platelets (lymphoglandular bodies) can be seen in most lymph node aspirates and represent cytoplasmic fragments.Reactive lymph nodes
Reactive lymph nodes are nodes that are responding to antigenic stimulation and/or inflammation in the region which they drain.
The majority of the lymphocytes in a reactive node should be small lymphocytes (smaller than a neutrophil or eosinophil) with smaller numbers of intermediate sized lymphocytes (about the size of a neutrophil) and even fewer numbers of lymphoblasts (large cells with prominent nucleoli). Plasma cell numbers are increased in reactive nodes and will vary from 5-25% of the total cell numbers in some areas of the slide. Increased plasma cell numbers are considered to be one of the hallmarks of reactive lymph nodes and are responding to antigenic stimulation. Plasma cells are characterized by a small, round, often eccentrically located nucleus that has a very coarse chromatin pattern and moderate amounts of basophilic cytoplasm. A perinuclear clear zone in the cytoplasm can often be seen. Inflammatory cells are often present in small to moderate numbers and may be neutrophils, eosinophils, mast cells or macrophages. Lymph nodes draining regions of cutaneous inflammation will often contain increased numbers of eosinophils and mast cells. Mast cell numbers should generally be less than three percent of the total cells in a reactive lymph node. A significant increase above those numbers warrants a search for a primary mast cell tumor.