Intracytoplasmic lumina in bladder carcinomas

Intracytoplasmic lumina were identified in neoplastic cells from four human and three canine "spontaneous" bladder carcinomas. They were also found in N-[4-(5-nitro-2-furyl)-2-thiazoly] formamide induced bladder carcinomas in rats as well as in cultured tumor cell lines derived from these experimental tumors. Intracytoplasmic lumina were readily recognized in 5 micrometer. paraffin embedded and 1 micrometer. epoxy embedded sections. Histochemically, intracytoplasmic lumina were strongly positive with PAS and alcian blue-PAS; mucicarmine stain was positive as unevenly distributed droplets. Ultrastructurally lumina were defined by a symmetric unit membrane; they displayed abundant pleomorphic microvilli, which contained prominent cytoskeletal elements. Step section electron microscopic study revealed continuity between intracytoplasmic lumina and the extracellular space in only one case of experimental bladder carcinoma; otherwise they appeared to be entirely encompassed within the cytoplasm. No instance of exocytosis in relation to intracytoplasmic lumina was found. Our observations suggest that intracytoplasmic lumina may be rather frequent in several forms of urothelial carcinoma. They appear to be predominantly but not invariably intracytoplasmic. The mechanism that may determine the development of continuity between intracytoplasmic lumina and the extracellular space and the adduced relationship between intracytoplasmic lumina and the process of secretion remain undetermined.