Abstract. Male breast cancer (MBC) is a rare disease, accounting for ~1% of all breast cancer cases worldwide. Although other genes are also involved, predisposing genetic factors to MBC include germline mutations in the BRCA genes (BRCA2). Among the other genes, partner and localizer of BRCA2 (PALB2) is considered a moderate-penetrance breast cancer susceptibility gene that may also play a role in MBC predisposition. Thus, the aim of the present study was to determine the PALB2 gene status in 8 MBC cases selected from a cohort of 181 hereditary breast and/or ovarian cancer probands. We performed PALB2 mutational analysis by direct sequencing of 13 exons and adjacent intronic regions. This study showed the presence of a PALB2 truncating mutation in 1/8 (12.5%) cases. This novel mutation was named c.1285_1286delAinsTC (p.I429SfsX12) and is localized in exon 4 of PALB2, in the region encoding for the ChAM motif which is important for the efficient association of PALB2 to chromatin and for recruitment of the BRCA complex to accumulate RAD51 at double-strand break sites. Our findings indicate that PALB2 could be added to the list of breast cancer susceptibility genes also in families with MBC cases.

Our observations support the hypothesis of a non-specific severe phenotype in DH carriers in terms of age of disease onset, cumulative lifetime risk and multiple primary tumours. Furthermore, our findings confirm that in order to identify all cases of DH, it is important not to limit the identification of mutations in a single gene, but extend the analysis to BRCA1 and BRCA2 and other breast cancer susceptibility genes.

In silico analysis conducted for S1341, IVS1-59t > c, IVS11-74insA and IVS12 + 74c > g of BRCA2 predicted the variants as neutral and benign, whereas the results for I1167V was inconclusive. mRNA analysis for the novel BRCA2 intronic variant IVS11-74insA and the already published BRCA1 variant C197 shows that they have no effect on the splicing. These results are in agreement with in silico analysis.

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