Bilateral malignant Brenner tumor: report of a case with ultrastructural study.

An unusual case of bilateral malignant Brenner tumor with liver and omental metastases is reported. The tumor was histologically a transitional cell carcinoma comparable to a grade III bladder carcinoma. A benign component was not identified, but there were a few nests of malignant epithelial cells distributed in a dense stroma, a pattern identical to that seen in a benign Brenner tumor. Whether this represents malignant change in a previously benign focus or a well differentiated part of a de novo carcinoma is unclear. Nevertheless it is suggested that the current histologic criteria for malignant Brenner tumor be modified to exclude the requirement of an intimately associated benign Brenner tumor. Ultrastructurally the malignant Brenner tumor has many features of the benign Brenner tumor. Some features, notably the basal lamina, micropinocytotic vesicles, nd intracytoplasmic microfibrils, are herein described for the first time in a malignant Brenner tumor.