Introduction

Intraductal carcinoma of the prostate (IDC-P) is characterized by malignant cells expanding the lumen of prostatic ducts and acini (Figure 1) (1). The basal cells are completely or partially preserved (Figure 2). The malignant cells filling the gland cause trabecular, cribriform, micropapillary or solid pattern (2,3,3,4,3,4,5). The glands with intraductal carcinoma are more than twice the diameter of normal peripheral zone glands and may show branching typically at the right angles (Figure 3). The contour of the glands is smooth in contrast to benign and high-grade prostatic intraepithelial neoplasia (H-PIN). There may be comedonecrosis (2). The cells show generally two different populations. The outer layer cells are pleomorphic with marked nuclear atypia and six times larger than benign nuclei. They are mitotically active and stain poorly for prostate specific antigen (PSA) immunohistochemically (1). The inner group cells are small (Figure 3). They are monomorphic cuboidal cells with abundant cytoplasm and strong PSA staining. There may be extracellular mucin (Table 1). The differential diagnosis of IDC-P includes cribriform H-PIN, invasive cribriform adenocarcinoma, ductal adenocarcinoma, and intraductal spread of urothelial carcinoma. H-PIN lacks solid and cribriform patterns, comedonecrosis, two different cell populations, and marked nuclear enlargement. Ductal adenocarcinoma has papillary structures with fibrovascular cores, and basal cells are usually absent. Cribriform adenocarcinoma shows irregular and invasive borders and absence of basal cells. Urothelial carcinoma with intraductal spread generally does not show cribriform pattern and the immunohistochemical staining profile is different (2,3). Spatial association, microinvasion, and similar molecular alterations in H-PIN and invasive carcinoma suggest H-PIN to be a precursor for low-grade cancers. High-grade prostate cancers are suggested to develop from either low-grade tumors or from H-PIN. Molecular alterations in high-grade prostate cancers and IDC-P are similar and IDC-P is suggested to evolve by the spread of high-grade cancer cells to preexisting ducts or develop de-novo from H-PIN. Therefore, IDC-P is a distinct entity from H-PIN (1). When intraductal carcinoma is diagnosed with a concomitant invasive carcinoma in a prostate biopsy, reporting may not make any sense. However, intraductal carcinoma is frequently associated with high-grade, high-volume prostate carcinoma and poor prognosis; represents the intraductal spread of high-grade cancer and points to advanced-stage disease (2) and recommended to be reported (3,4). However, it is very critical to report when there is no concomitant invasive carcinoma. In these cases, IDC-P should be reported with a comment stating its association with high-grade and high-volume cancer with a recommendation of either a definitive therapy or immediate repeat biopsy (3,4,4,5). Key Words: Prostate, intraductal, carcinoma, carcinoma in situ Anahtar Kelimeler: Prostat, intraduktal, karsinom, karsinoma in situ Concept: Kutsal Yörükoglu Design: Kutsal Yörükoglu Data Collection or Processing: Kutsal Yörükoglu Analysis or Interpretation: Kutsal Yörükoglu Literature Search: Kutsal Yörükoglu Writing: Kutsal Yörükoglu Peer-review: Internal peer-reviewed. Conflict of Interest: No conflict of interest was declared by the authors. Financial Disclosure: The authors declared that this study has received no financial support.