THE NESTED VARIANT OF TRANSITIONAL-CELL CARCINOMA - AN AGGRESSIVE NEOPLASM WITH INNOCUOUS HISTOLOGY

The nested variant of transitional cell carcinoma (TCC-NV) is a rare n eoplasm; only eight cases have been described. This report reviews the clinicopathologic features of 16 additional examples. The cases were collected from consultations received during a 13-year period. In most instances, a consultation was sought because the histologic features suggested an atypical proliferation of Brunn's nests or a lesion simil ar to the previously published examples of TCC-NV. Clinical data were gathered and tissues were studied to exclude prostatic cancer and aden ocarcinoma TCC-NV is characterized by the presence of irregular nests and/or tubules of transitional cells infiltrating the lamina propria w ithout surface involvement Neoplastic cells tend to have innocuous fea tures but at least a few cells in every case are cytologically anaplas tic. There is a marked male predominance. Synchronous or metachronous TCCs of more usual histologic make-up may occur. After a follow-up ave raging 16.6 months, only three patients are known to be alive with no evidence of disease. Clinicopathologic information from our 16 cases c ombined with the 8 previously reported examples confirms that TCC-NV i s a persistent and aggressive neoplasm notable for its innocuous appea rance in histologic preparations.