Invasion patterns of metastatic high-grade serous carcinoma of ovary or fallopian tube associated with BRCA deficiency.

High-grade serous carcinomas of the uterine adnexa with BRCA1 deficiency (high-grade serous carcinomas-BRCA) have recently been described to demonstrate characteristic histopathological features. We hypothesize that metastatic high-grade serous carcinomas-BRCA cases exhibit characteristic morphological features as well. We studied 102 high-grade serous carcinomas with known BRCA1 and BRCA2 genotype from the archives of the Department of Pathology at Memorial Sloan-Kettering Cancer Center. The primary site morphological characteristics of these cases were reported previously; we now focus solely on tumor morphology in sites other than the uterine adnexa (ie, metastatic sites). The study group consisted of the following case types: 13 BRCA1 germline mutations; 5 BRCA1 somatic mutations; 10 BRCA1 promoter methylation; 4 BRCA2 germline mutations; 1 BRCA2 somatic mutation; 11 lacking BRCA1 or BRCA2 abnormality; 58 cases lacking BRCA1 or BRCA2 germline mutation. Two observers independently scored invasion patterns and microscopic tumor architecture while blinded to genotype. Concordance between observers and correlations between metastatic patterns and the following indices were studied: genotype, primary site tumor characteristics, and BRCA1 immunohistochemistry. Concordance between observers was excellent (κ values >0.9). All cases with BRCA1 or 2 abnormalities showed either pushing pattern metastases (76%) or infiltrative metastases composed only of micropapillae (24%). In contrast, all cases lacking BRCA1 or 2 abnormalities showed infiltrative metastases that contained combinations of papillary, glandular, and, rarely, cribriform and micropapillary architecture (P<0.0001 for comparison with pushing metastasis and P<0.001 for comparison with purely micropapillary architecture). Morphological assessment of metastatic carcinomas, a highly reproducible exercise, accurately correlated with BRCA1 status in every case, unlike morphological assessment of primary site adnexal high-grade serous carcinomas or BRCA1 immunohistochemistry. Metastatic high-grade serous carcinomas-BRCAs exhibit characteristic morphological features that appear more sensitive and specific for BRCA mutations than two other morphologically based prediction systems and should be easier to apply in practice. These findings should be validated prospectively in an independent cohort.