Clinical and Morphological Features of gPALB2-Associated Breast Cancer in the Russian Population

The analysis included 3,800 cases of breast cancer. Next-generation sequencing (NGS) of DNA extracted from peripheral blood leukocytes revealed mutations in the gPALB2 gene in 39 (1.03%) patients. The most frequent mutations were c.509_510del (25.64%), c.1592del (20.51%), and c.172_175del (10.26%). The predominant histological variant was invasive ductal carcinoma (84.62%) with moderate differentiation (G2) (48.72%). In most cases, luminal HER2^- subtype (69.23%) was revealed, HER2⁺ and triple-negative were less frequent (12.82 and 17.95%, respectively). Neoadjuvant chemotherapy was administered to 9 patients; a clinical response observed in 100% of cases. RCB-0 (pCR) was noted in 33.3%; RCB-I in 11.1%, RCB-II in 44.4%, and RCB-III in 11.1% of observations. All recorded cases of contralateral breast cancer (10.26%) were metachronous and presented as estrogen receptor-positive HER2^- tumors.