Peripherally localized benign hyperplastic nodules of the prostate.

Approximately one-half of needle-core biopsy samples performed for palpable and/or ultrasonographically hypoechoic focal lesions of the prostate reveal carcinoma. A fraction of the negative biopsy samples are related to benign hyperplastic nodules, localized in the peripheral zone of the prostate. The present study examines the morphology of this particular lesion in surgical specimens obtained after cystoprostatectomy and radical prostatectomy performed for bladder and (small) prostate cancer, respectively. Peripheral hyperplastic nodules occur in 18.5% of this population and are unifocal in one-half of the cases. The mean diameter is 4 (+/- 1.3) mm. Peripheral hyperplastic nodules are characteristically localized posteriorly in the peripheral zone, between the midline and the lateral border of the prostate and often in the vicinity of the boundary of the transition zone. Histologically, they resemble glandulostromal hyperplastic nodules as observed in classic benign nodular hyperplasia of the transition zone. Cystic transformation may occur. The nodules are sometimes surrounded by condensed stroma and atrophic glands. Atypical adenomatous hyperplasia is rarely noticed in this lesion. No pure stromal (leiomyomatous) nodules without glands are seen. The peripheral hyperplastic nodule should be included in the differential diagnosis of focal lesions of the peripheral zone.