Cytology of plasma cell rich effusion in cases of plasma cell neoplasm

Background: Multiple myeloma or plasmacytoma resulting in malignant effusion is rarely described in literature. Aims: In this paper, we have studied the seven rare cases of plasma cell infiltration in effusion fluid. Materials and Methods: We studied six cases of pleural fluid and one case of ascetic fluid. Detailed cytological features, clinical history, bone marrow examinations, serum electrophoresis, and immunofixation data were analyzed. Result: There were two cases of plasmacytoma, four cases of multiple myeloma, and one case of plasmablastic lymphoma. On cytology, all the cases showed excess plasma cells along with mesothelial cells and lymphocytes on effusion cytology smear. Conclusion: Plasma cell rich effusion in cases of plasma cell tumor is rare. However, on cytology these cases do not pose much problem if relevant history is known.