Figure 2.

Examination of the initial thoracentesis fluid demonstrated scattered large atypical lymphoid cells with multilobated nuclei, vesicular chromatin and multiple prominent nucleoli (arrows), in a background of benign mesothelial cells, histiocytes, small lymphocytes and neutrophils ((a), left, May-Grünwald-Giemsa, and right, hematoxylin and eosin). The corresponding cell block specimen showed similar findings (hematoxylin and eosin). Immunohistochemical stains showed the scattered large cells to be positive for CD20 (c) and kappa light chain-restricted (d), with few lambda-positive cells in the background (e). A repeat thoracentesis specimen taken 1 month later showed no evidence of malignancy, with only benign mesothelial cells (arrow) and hematopoietic elements (Wright-Giemsa).