Morphogenesis of inclusion bodies of urothelial carcinoma: a case study

The morphogenesis of inclusions of urothelial carcinoma (K. Donhuijsen et al.: Hum Pathol 23:860, 1992) is described in a case of a 51-year-old man with poorly differentiated urothelial carcinoma. Peritoneal fluid preparations contained numerous dyscohesive, large, anaplastic cells with abundant dense amphophilic cytoplasm often compartmentalized into multiple, variably sized, intracytoplasmic lumina, each containing "bull's eye"-like inclusions, with a periodic acid Schiff-positive refractile central core and an alcian blue/mucicarmine-positive rim. Ultrastructurally, the progression of osmiophilic substance from membrane-bound exocrine-type secretory granules, via exocytosis, to a presence in both intracytoplasmic lumina and extracellular space has been documented. Immunohistochemically, the periodic acid Schiff-positive refractile cores, as well as the minute periodic acid Schiff-positive granules in the cytoplasm, stained positively for secretory component and peanut agglutinins, whereas the alcian blue-positive mucinous material, which coated the refractile cores as well as the lining of the intracytoplasmic lumina, stained strongly for epithelial membrane antigen and leu M1. Ultrastructurally, protein A-gold probes, immunolabeled for peanut agglutinin and secretory component, were localized to the osmiophilic substance.