Transitional cell carcinomas of the urinary bladder that may be underdiagnosed. A report of four invasive cases exemplifying the homology between neoplastic and non-neoplastic transitional cell lesions.

Four unusual invasive transitional carcinomas of the urinary bladder arose in patients aged 70 to 85 years. One or more specimens from each case were misinterpreted as benign. The features that led to diagnostic confusion included nests and trabeculae composed of cells with relatively bland cytologic features and small tubules, medium-sized glands, or cysts that suggested nephrogenic adenoma, cystitis glandularis, or cystitis cystica. In three cases, elongated slit-like lumens or clefts that frequently branched were also present, and several tumors had nests with pointed projections from which neoplastic cells invaded into the adjacent stroma in an often inconspicuous manner. In addition to their unusual patterns and frequent deceptive cytologic features, the tumors were noteworthy because they often had cells with abundant eosinophilic cytoplasm. A variety of architectural features, specifically a disorderly distribution of the epithelial elements, their frequent packed arrangement, and their variation in size and shape, all spoke for a neoplastic interpretation in the current cases. Additionally, in most of these cases, small clusters of cells or individual cells of more conventional invasive carcinoma facilitated the interpretation. The results of the study of these four cases expand the spectrum of recently described peculiar features of transitional cell carcinoma of the urinary bladder. Several of the findings in these tumors exemplify the parallels that exist between nonneoplastic epithelial abnormalities and transitional cell carcinoma of the bladder.