Stage A versus stage B adenocarcinoma of the prostate: morphological comparison and biological significance.

Morphological features in radical prostatectomy specimens from 11 stage A and 73 stage B prostatic carcinomas were compared by mapping of tumor locations, and determinations of cancer volumes and histological patterns. Small stage A cancers were located anteromedially, while small stage B carcinomas were concentrated against the posterior capsule at the rectal surface. Small stage A carcinomas commonly invaded the anterior fibromuscular stroma and benign prostatic hyperplasia nodules, features that were uncommon even in large stage B tumors. Stage A cancers often appeared to arise within benign prostatic hyperplasia nodules and had a distinctive histological appearance. Even when large, stage A carcinomas tended not to spread close to the rectal surface of the gland. Stages A and B cancers spanned a roughly comparable volume range, and both showed progressive dedifferentiation with increasing volume. It is proposed that stages A and B cancers are biologically similar malignancies, distinguished only by their site of origin. Prognosis for patients with stage A carcinoma probably is closely related to tumor volume and dedifferentiation, features that are not reliably estimated in tissue samples removed at operation for benign prostatic hyperplasia.