High Grade Prostatic Intraepithelial Neoplasia and Atypical Glands

Historically, high-grade prostatic intraepithelial neoplasia (HGPIN) has been considered a premalignant lesion characterized by atypical proliferation and nuclear features in the setting of benign appearing acini and ducts. Rates of concurrent cancer after initial sextant biopsy diagnosis of HGPIN in the past were much higher due to undersampling, resulting in increased rates of cancer detection with immediate repeat biopsy. Currently, improved identification of smaller foci of cancer with initial extended core prostate biopsy has obviated the need for repeat biopsy in most patients diagnosed with HGPIN, given a similar cancer detection rate to those with a completely benign baseline biopsy. The exception is the subset of patients found to have multifocal HGPIN who continue to be at increased risk for subsequent cancer detection.In contrast, atypical small acinar proliferation (ASAP) is a diagnostic category signaling the presence of pathologic features suspicious but not definitive for malignancy. The most common cause for this diagnostic ambiguity is small size of the foci of atypical glands. Frequently, this diagnosis represents undersampling of concurrent adenocarcinoma, thus the rate of subsequent cancer diagnosis is high, ranging from 27% to 71%. As a result, expert consensus suggests that patients with this finding on initial biopsy should be followed closely and undergo at least one short interval repeat biopsy for risk restratification.