Cytologic features of ascites in malignant fibrous histiocytoma of the colon

The cytologic features of ascitic fluid in a case of malignant fibrous histiocytoma (MFH) of the colon are described. At autopsy, two solid tumor masses were found around the ascending and transverse colon, accompanied by about 3,000 ml of ascites. Tumor cells had infiltrated diffusely into the outer layers of almost all of the gastrointestinal wall, simulating peritonitis carcinomatosa. Cytologic examination of the ascites revealed various kinds of tumor cells; short spindle-like cells, multinucleated giant cells, and round cells with an invaginated nuclear margin, forming small clusters. These cytologic findings were considered to be very useful in the diagnosis of MFH, especially in cytologic examinations of ascites.