Inverted papilloma of the urinary bladder: ultrastructural and immunologic studies.

The histologic, ultrastructural, and immunologic features of an inverted urinary bladder papilloma were studied with thin-section and freeze-fracture electron microscopy, a specific red blood cell adherence test, and through analysis of urine carcinoembryonic antigen (CEA). The increased number of gap junctions and desmosomes, the presence of thickened and reduplicated basal laminae, and the normal CEA levels found in association with this neoplasm, correlate well with its generally predictable benign behavior.