Assessment of the Reporting and Incidence of Prostate Cancer Unconventional Histologies in Tertiary Referral Institutions: An Under-reported but Exploding Phenomenon?

Prostate cancer (PCa) with unconventional histologies (UHs) is not infrequent and may be associated with different prognosis compared with conventional PCa depending on the type, subtype, or pattern considered. A recent World Health Organization update recommends UHs to be reported on biopsy and final pathology. Our study aimed to assess the incidence and reporting attitudes of PCa UHs at tertiary referral institutions. Overall, 22 and 11 centers provided data on internal pathological guidelines and/or UH incidence, respectively. A comprehensive list of UHs was reported by pathologists only in <50% of the centers. Of note, ductal, intraductal, cribriform, and sarcomatoid UHs were consistently reported in ≥85% of the centers. The incidence of UHs was 373 on 15 605 biopsies (2.4%) and 737 on 14 945 (4.9%) final pathology specimens. However, UH incidence at final pathology increased from 0.7% in 2010 to 19% in 2023, while it remained stable on biopsy (1.5% in 2010 and 2.1% in 2023). The most frequent UH was cribriform (64%), followed by ductal (10%) and intraductal (9%) PCa. In conclusion, UHs are not infrequent and their recognition is increasing. However, pathological reporting is not well standardized, and prostate biopsies likely underestimate UHs.