ATM immunohistochemistry as a potential marker for the differential diagnosis of no specific molecular profile subtype and POLE-mutation subtype endometrioid carcinoma.

Ancillary immunohistochemical tools can facilitate an integrated diagnosis of endometrial pathology. According to The Cancer Genome Atlas classification, endometrial cancers are of four molecular subtypes: mismatch repair (MMR)-deficient (MMR-d), p53 mutation (p53mut), DNA polymerase epsilon (POLE) mutation (POLEmut), and no specific molecular profile (NSMP). As the specific histological and immunohistochemical features of POLEmut and NSMP subtypes are unknown, these cancers are categorized based on molecular analysis. In this study, we analyzed POLEmut-subtype endometrioid carcinoma (EC) using a custom-made cancer gene panel and the Catalog of Somatic Mutations in Cancer (COSMIC) database, extracted a characteristic genome profile, and identified an immunohistochemical marker that could be used as a diagnostic tool. The results indicated that the POLEmut-subtype EC exhibited nonsense mutations in the ataxia telangiectasia mutated (ATM) gene and a subsequent loss of ATM expression, which was monitored through immunohistochemical analysis. Moreover, analyses using the COSMIC database indicated that POLEmut-subtype EC cases often harbored similar ATM nonsense mutations. These results suggest that ATM expression is a potential immunohistochemical marker for the differential diagnosis of POLEmut- and NSMP-subtype EC. DATA AVAILABILITY: The data supporting the findings of this study are available upon request from the corresponding author. The data are not publicly available because of privacy or ethical restrictions.