Prostatic stromal hyperplasia with atypia: follow-up study of 18 cases.

CONTEXT: Prostatic stromal hyperplasia with atypia is a rare lesion that can be mistaken for sarcoma because of the presence of atypical, bizarre, degenerative myocyte nuclei.

OBJECTIVE: To determine the diagnostic criteria and clinical significance of prostatic stromal hyperplasia with atypia.

DESIGN: Eighteen cases of prostatic stromal hyperplasia with atypia were reviewed from the consultation file of one of the authors (D.G.B.).

RESULTS: Prostatic stromal hyperplasia with atypia consists of 1 or more ill-defined, uncircumscribed, hyperplastic stromal nodules, with variable numbers of atypical, bizarre giant cells, with vacuolated nuclei, smudged chromatin, and frequent multinucleation infiltrating around benign acini. There was a hypocellular, loose, myxoid stromal matrix, with ectatic hyalinized vessels and mild to moderate chronic inflammation. Stromal cells displayed intense immunoreactivity for androgen receptors and vimentin, but moderate reactivity for desmin and actin. There were 3 local recurrences, with a mean follow-up of 6.3 years (range, 0.5-14 years), but none developed evidence of sarcomatous transformation or malignancy.

CONCLUSIONS: Prostatic stromal hyperplasia with atypia is a rare, benign lesion, composed of degenerative myocytes with atypia that is histologically and clinically reminiscent of benign counterparts in the myometrium, breast, vulva, vagina, and elsewhere. Recognition of this distinctive entity should allow separation from phyllodes tumor and sarcoma of the prostate. The phrase stromal tumor of uncertain malignant potential is inappropriate for this benign tumor, and its use is discouraged.