Intraductal histiocytes as a simulant of intraductal carcinoma of the prostate.

Abstract

Contemporary reporting guidelines require assessment for intraductal carcinoma of the prostate (IDC-P), given its recognition as an adverse prognostic factor. While several benign and malignant mimickers of intraductal carcinoma have been reported and studied, the potential for intraductal aggregates of histiocytes to simulate or complicate assessment of this process has not been addressed in the literature. The authors performed a retrospective multi-institutional review of challenging prostate lesions in which intraductal histiocytic aggregates simulated involvement by IDC-P. Pathology reports and slides were reviewed by 3 fellowship-trained genitourinary pathologists, and clinicopathologic features, immunohistochemistry use, and relative difficulty of the diagnosis were assessed. A total of 47 cases of intraductal histiocytes simulating IDC-P were identified, including 27 needle biopsy, 9 transurethral resection, and 6 radical prostatectomy cases. Overall, 19 cases showed histiocytic aggregates in cases with carcinoma, while 28 occurred in otherwise benign settings. Immunohistochemistry was performed in 14 cases for resolution of the diagnosis. When categorized by the authors in terms of difficulty of the diagnosis, 20 of 47 cases were considered "moderate" or "difficult." Based on their solid appearance spanning an intact duct, aggregates of histiocytes within prostatic ducts may closely simulate IDC-P. Given the prognostic significance of IDC-P, this potential pitfall merits consideration and targeted use of immunohistochemistry in challenging cases.