Atypical Intraductal Proliferation and Intraductal Carcinoma of the Prostate on Core Needle Biopsy: A Comparative Clinicopathological and Molecular Study with a Proposal to Expand Morphological Spectrum of Intraductal Carcinoma

Abstract

Aims

Atypical intraductal proliferation (AIP) of the prostate is histologically worse than high-grade prostate intraepithelial neoplasia, but lacks the diagnostic criteria of intraductal carcinoma (IDC-P). The study aims to compare clinicopathological and molecular characteristics (ERG overexpression and PTEN loss) of AIP and IDC-P in core needle biopsies.

Methods and Results

Total 106 (84 (5.6%) of 1480 consecutive and 22 retrospectively collected) cases met the criteria: AIP only (2.4%), IDC-P only (1.3%), and IDC-P coexisting with AIP (2%). Invasive adenocarcinoma (PCa) was present in 96% and 97% cases of AIP and IDC-P respectively. The mean number of glands/focus and the largest gland diameter for AIP and IDC-P were 7.6 (range, 2-27) and 11.7 (range, 1-51) and 0.59 MM (range, 0.2-1.1) and 0.75 MM (range, 0.2-1.8) respectively. For AIP, loose cribriform architecture was the most common (93%) morphology. IDC-P associated PCa had more aggressive pathology including highest combined Gleason score (GS), high-grade GS ≥ 4+3, largest % involvement of core by PCa and % positive cores than AIP associated PCa (p<0.05). Within AIP group, ERG and PTEN status was similar to adjacent PCa in 97% and 88% of cases respectively. Within IDC-P group, ERG and PTEN status was similar among IDC-P, AIP and PCa in 96% and 91% of cases respectively. PTEN loss was frequently heterogeneous in PCa and localized adjacent to AIP or IDC-P

Conclusions

AIP represents lower-grade morphological spectrum of IDC-P associated with an intermediate risk PCa. Patients with only AIP need immediate repeat biopsy to rule out clinically significant PCa.

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