Intraductal Carcinoma of the Prostate: Emerging Support for a Unique Diagnostic EntityIczkowski, Kenneth A. MDPathology Case Reviews: May/June 2014 - Volume 19 - Issue 3 - p 178–183 doi: 10.1097/PCR.0000000000000036 Case Reviews Abstract Author Information Abstract: The concept of intraductal carcinoma (IDC) of the prostate was developed in the 1990s. IDC, like high-grade prostatic intraepithelial neoplasia (HGPIN), consists of medium to large caliber duct spaces that retain a basal cell layer. However, the cells in IDC span the lumen of a duct space, and the cellularity and degree of nuclear pleomorphism exceed that assigned to HGPIN. It was not until recent years that IDC received much attention, after several molecular studies showed that IDC has rates of TMPRSS2-ERG gene fusion, PTEN loss, and Ki-67 proliferation index that are comparable to invasive acinar carcinoma and much higher than those of HGPIN. The criteria for IDC in the literature are at variance, and standardization is needed. IDC can have several variations, including small cell change. We add a case of IDC with small cell change to the 7 reported in prior literature; but our case is the first to show reactivity for a neuroendocrine marker. From the Medical College of Wisconsin, Milwaukee, WI. Reprints: Kenneth A. Iczkowski, MD, Department of Pathology, Medical College of Wisconsin, 9200 W. Wisconsin Ave, Milwaukee, WI 53226. E-mail: firstname.lastname@example.org. The author has no funding or conflicts to declare. © 2014 by Lippincott Williams & Wilkins.