Anaplastic solitary extramedullary plasmacytoma of the cecum. Report of a case confirmed by immunoperoxidase staining.

Solitary extramedullary plasma cell tumors, although uncommon, have been reported with increasing frequency over the last few years. Approximately 5 to 10 percent of the tumors arise in the gastrointestinal tract. This report demonstrates that a solitary anaplastic cecal extramedullary plasmacytoma can mimic a polypoid carcinoma, both grossly and, to an extent, microscopically. Immunoperoxidase stains for cytoplasmic immunoglobulin proved useful in establishing the correct diagnosis.