Cytologic detection of malignant lymphoma cells with a hairy appearance in ascitic fluid. Report of a case with immunofluorocytometric analysis.

Neoplastic lymphocytes with a hairy appearance were detected in the ascitic fluid from a case of retroperitoneal malignant lymphoma. Although the tumor cells resembled those of hairy-cell leukemia (HCL), no leukemic change was observed, and the anatomic location of the neoplastic cells was different from that seen in HCL. The tumor cells were positive for some immunohistochemical markers of HCL (i.e., CD1 9 and SIg) but were negative for others (CD11c, CD25 and tartrate-resistant acid phosphatase). Immunocytofluorometric and postmortem histologic studies showed the lesion to be a well-differentiated B-cell lymphocytic lymphoma with plasmocytic differentiation in some cells.