Plasmacytoid transitional cell carcinoma. Report of a case with initial presentation mimicking multiple myeloma.

The case of a 63-year-old man with a previously undescribed morphologic variant of transitional cell carcinoma of the urinary bladder is reported. The patient initially presented with multiple lytic bony metastases of the ribs and skull. Aspiration biopsy of one of the lytic lesions of the skull showed tumor cells with a striking plasmacytoid appearance, similar to the plasma cells seen in myeloma, leading to an initial observer's diagnosis of multiple myeloma. Subsequently, a bladder tumor with the same cytomorphology was found; immunohistochemical and ultra structural studies performed on the aspirated material and on the bladder biopsy specimen clearly established the epithelial nature of this neoplasm.