[Benign microglandular prostate lesions. Diagnostic criteria na differential diagnosis].

The scope of the present review is to define diagnostic criteria of benign prostatic lesions causing diagnostic difficulty in surgical pathology. The prostate harbors a variety of small acinar lesions that may mimic prostate cancer in biopsy specimens. Generally, the most important diagnostic clues are obtained on low-power magnification by assessing architectural features. Atypical adenomatous hyperplasia (AAH) is a small acinar proliferation closely related to hyperplastic glands. Diagnostic features of postatrophic hyperplasia include a lobular small acinar proliferation associated with atrophic and dilated acini. Basal cell hyperplasia and sclerosing adenosis show characteristic stromal changes that are uncommon in prostate cancer. Additional cytological features and intraluminal secretions are also important in the diagnostic evaluation of small acinar lesions in biopsy specimens. Negative immunohistochemical results obtained with basal-cell-specific cytokeratins should be evaluated in context with other diagnostic criteria. The unequivocal demonstration of basal cells in small acinar lesions excludes invasive cancer. Other rare small acinar lesions must be recognized when assessing biopsy specimens, including verumontanum-mucosa hyperplasia, Cowper's glands and mesonephroid hyperplasia. The various small acinar lesions discussed in the present review have no clinical significance, except atypical adenomatous hyperplasia (AAH), which may be a precursor of small acinar cancer of the transition zone. The biological and clinical significance of AAH, however, remains to be established.