Intraductal carcinoma of prostate: a comprehensive and concise review.

Intraductal carcinoma of the prostate (IDC-P) is defined as a proliferation of prostate adenocarcinoma cells distending and spanning the lumen of pre-existing benign prostatic ducts and acini, with at least focal preservation of basal cells. Studies demonstrate that IDC-P is strongly associated with high-grade (Gleason grades 4/5), large-volume invasive prostate cancers. In addition, recent genetic studies indicate that IDC-P represents intraductal spread of invasive carcinoma, rather than a precursor lesion. Some of the architectural patterns in IDC-P exhibit architectural overlap with one of the main differential diagnoses, high-grade prostatic intraepithelial neoplasia (HGPIN). In these instances, additional diagnostic criteria for IDC-P, including marked nuclear pleomorphism, non-focal comedonecrosis (>1 duct showing comedonecrosis), markedly distended normal ducts/acini, positive nuclear staining for ERG, and cytoplasmic loss of PTEN by immunohistochemistry, can help make the distinction. This distinction between IDC-P and HGPIN is of critical importance because IDC-P has an almost constant association with invasive carcinoma and has negative clinical implications, including shorter relapse-free survival, early biochemical relapse, and metastatic failure rate after radiotherapy. Therefore, IDC-P should be reported in prostate biopsies and radical prostatectomies, regardless of the presence of an invasive component. This article will review the history, diagnostic criteria, molecular genetics, and clinical significance of IDC-P.