Histologic classification of prostate cancer.

Apart from the typical acinar morphology observed in more than 90% of prostatic adenocarcinomas, a spectrum of morphological variants and prostate cancer subtypes exists. Two nosologically different groups can be distinguished: the variants of conventional acinar cancer and cancers with histological pattern, which are unusual for the prostate. Variants of conventional prostate cancer (pseudohyperplastic, foamy gland, hypernephroid, atrophic, microcystic, with Paneth cell-like changes, with collagenous micronodules, with glomeruloid formations, oncocytic) do not have any known prognostic significance and are graded according to the Gleason system. Unusual cancer types (ductal carcinoma, mucinous [colloid] carcinoma, mucinous signet ring cell carcinoma, small cell carcinoma, sarcomatoid carcinoma and carcinosarcoma, pleomorphic giant cell carcinoma, squamous and adenosquamous carcinoma, basal cell and adenoid cystic carcinoma, lymphoepithelioma-like carcinoma, primary urothelial carcinoma of the prostate) have mostly a very poor prognosis and are therefore real nosological entities.