Diagnosis: Intraductal carcinoma of the prostate
• Intraductal carcinoma of the prostate is defined as the presence of solid or dense cribriforming architecture within native ducts or glands containing a basal cell layer. In addition, a loose cribriform or micropapillary proliferation could be considered as part of the spectrum of intraductal carcinoma if marked nuclear pleomorphism is present, defined as sixfold enlargement of the nuclei.
• The importance of intraductal carcinoma is when it is the only finding seen on needle core biopsies of the prostate with no documentation of concurrent or previous invasive carcinoma, such as the case in this patient. An immediate rebiopsy is recommended, since intraductal carcinoma is usually associated with poorly differentiated invasive adenocarcinoma with poor prognostic features on radical prostatectomy. This patient was subsequently diagnosed with prostatic adenocarcinoma Gleason score 8(4 + 4) with a tertiary component of Gleason grade 5 on radical prostatectomy.
• The differential diagnosis of intraductal carcinoma of the prostate usually includes high grade prostatic intraepithelial neoplasia (HGPIN) and invasive ductal adenocarcinoma of the prostate. The differentiation from the latter can be easily performed through immunohistochemical markers for basal cells, which are usually conserved in intraductal carcinoma. The distinction from HGPIN is trickier and depends on the presence of marked architectural complexity and/or cytologic atypia, as discussed above.
• In rare cases where the findings appear borderline between HGPIN and intraductal carcinoma, this should be reflected in the surgical pathology report and perhaps an immediate repeat of the prostate biopsy is justified.
