The importance of histomorphological features and ERG expression in the diagnosis of malignancy in cases with atypical small acinar proliferation

Background: Atypical small acinar proliferation (ASAP) cases typically require rebiopsy, which are invasive and associated with increased risk of complications. Our aim in this study was to determine the importance of laboratory and histological findings and E-26 transformation-specific-related gene (ERG) expression in the diagnosis of malignancy. Methods: Between March 2016 and March 2022, 84 patients who were diagnosed with ASAP on biopsy or rebiopsy were included in the study. Clinical-laboratory features of age, serum prostate-specific antigen level, and histopathological features were compared and included multifocality, number of suspicious acini, nuclear enlargement, nucleolar prominence, hyperchromasia, cytoplasmic amphophilia, luminal amorphous acellular secretion, crystalloid presence, infiltrative appearance, inflammation, atrophy, α-methyl acyl-CoA racemase, p63, and/or high molecular weight cytokeratin were analyzed. In addition, ERG expression was evaluated immunohistochemically. Results: Statistically significant correlation was found between nucleolar prominence, nuclear hyperchromasia, crystalloid presence, infiltrative pattern, and prostate cancer (p < .001). In 19 of 84 cases (22.6%) ERG was positive in the nucleus. Prostate cancer was diagnosed at rebiopsy in 15 of the 19 ERG-positive cases (78.9%). A statistically significant correlation was found between ERG positivity and prostate cancer (p= .002). Conclusions: Our findings suggest that evaluation of these markers during initial transrectal ultrasound biopsies may decrease and prevent unnecessary prostate rebiopsy.