OBJECTIVETo evaluate the value of cytomorphologic and immunocytochemical approaches in the diagnosis of hematologic neoplasms in serous effusion.

METHODSThe cytospin and Thinprep smears of effusion specimens were prepared from 23 cases of lymphoid malignancies with histological confirmation and 30 cases of benign effusions used as control. Morphological assessment of the cellular components was conducted, including the ratio of mesothelium to lymphocyte, karyomorphism of lymphoid cell and the presence of apoptosis and mitosis. Immunocytochemical study was performed in all the cases, with flow cytometry in one case.

RESULTSAmong the 23 tumor cases, 14 represented disease relapse, and in the remaining nine cases, the serous effusion was the primary manifestation. The proportion of mesothelium was low in the tumor group, being less than 10% in 20 cases (87.0%, 20/23). It was more than 10% in most of benign cases (20/30, 66.7%). Lymphoid cells were prominent (> 80% cells) in 69.6% of the tumor cases, and the cellular component in some control cases (63.3%, 19/30) showed fewer lymphocytes. Nipple-like projection of lymphocytic nuclei could be detected in almost all the tumor cases (91.3%, 21/23), but was occasionally found in the control group (26.7%, 8/30). Apoptosis and mitosis were obvious in lymphomatous effusion, but observed in only 6.7% of the control cases. Significant difference of the previously mentioned cytomorphologic features existed between the tumor and control groups (P < 0.01). The results of immunocytochemical staining in cell block were identical to the corresponding immunohistochemistry, and one case of mantle cell lymphoma was confirmed by flow cytometry. The cytologic findings seen in all the 23 studied cases were in agreement with the corresponding histologic diagnosis.

CONCLUSIONSSome cytomorphologic features, including decreased number of mesothelium, increased number of lymphoid cells, nuclear nipple-like projection, and the presence of apoptosis and mitosis, are very useful for diagnosing lymphoid malignancy in serous effusion. Immunocytochemistry is an important approach to the cytodiagnosis and classification of lymphoma.