Transitional cell carcinoma with intracytoplasmic lumina ("signet-ring" cells) of bladder.
The ultrastructural characteristics were those of a moderately differentiated transitional cell carcinoma with intracytoplasmic structures distinct from the usual intracytoplasmic lumens responsible for the "signet ring" cells of adenocarcinomas, e.g., of the gastrointestinal tract (1). Intracytoplasmic lumens in the latter are characterized by more rigid microvilli that are associated with mucin secretion, glycocalyx and often microfilamentous core rootlets. In the present case, the surface projections resemble more those characteristic of normal transitional (squamous) urothelium. Here, between the desmosomes, many, narrow, curving filopodia project into widened intercellular spaces (2). Intracytoplasmic lumens have been described in transitional cell carcinomas (3).
These findings are important since primary adenocarcinomas of the urinary bladder behave poorly, compared to transitional cell carcinomas, and are treated by different oncologic protocols. The ultrastructural features also assist in eliminating a diagnosis of urachal adenocarcinoma, where mucigen granules and glandular differentiation are obvious. The rather uniform nature of cellular and nuclear features at the ultrastructural level tended to suggest that this bladder carcinoma was not particularly high-grade. This aspect seemed borne out by the cystectomy findings where only minimal invasion of the submucosa was identified.
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