Nephrogenic adenoma.

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.