Nephrogenic adenoma is a peculiar reactive process of urothelium which may occur anywhere along the urinary collecting system but rarely if ever arises in the absence of a preexisting urogenital abnormality. Although its histogenesis and biological potential have not been entirely defined, the evidence strongly suggests a metaplastic lesion comprising immature cells which lack the capacity to invade or metastasize. Clinical signs and symptoms are nonspecific and may relate more to the coexisting abnormality than to the nephrogenic adenoma itself. Although nephrogenic adenomas may resemble certain types of urologic malignancies, their histology is distinctive and varies little from lesion to lesion so that once the entity is considered, an accurate pathologic diagnosis is rarely a problem.

Although current methods of histologic substaging for incidental prostatic carcinoma are useful, they offer only general indications of potential tumor behavior. To further define the biologic tendencies of stage A cancers, an examination was made of the role of DNA ploidy combined with histologic staging in archival material selected to achieve both a representative sample and long-term follow-up. With histology alone, 36% of stage A2 cancers and 9% of A1 neoplasms were progressive. Adding DNA flow cytometry to histology resulted in a significant improvement in the capacity of pathologic evaluation to predict outcome. Progression occurred in 67% of aneuploid stage A2 prostate cancers and in none of the nonaneuploid stage A1 tumors. Despite current limitations in the interpretation of DNA histograms from archival tissue, flow cytometry has significant potential in the pathologic evaluation of incidental prostatic carcinomas.

The close neural-epithelial interaction seen in cases of prostatic carcinoma often is a criterion for malignancy. In a retrospective histological study of 26 nonneoplastic prostate glands obtained at autopsy benign glands were found in the perineural spaces in 6. In 5 of these cases the glands were cytologically benign, with a double layer of epithelial cells without nuclear pleomorphism, hyperchromatism and eosinophilic nucleoli. The remaining case involved an atrophic gland. Owing to the small size, nuclear hyperchromatism and, sometimes, crowded architectural arrangement atrophic glands may mimic malignant glands. This could be a potential cause of concern for the surgical pathologist when these glands appear around nerves. Perineural invasion should be interpreted cautiously when used as a criterion for malignancy.