Our Pan-Cancer analysis using 34 burden test genes-of-interest and 54 cancer-associated genes with recurrently mutated somatic variants (frequency ≥5 across cancer types) detected significant mutual exclusivity between BRCA1/BRCA2 germline truncations and IDH1 somatic mutations, which is likely confounded by cancer-type specificity: BRCA1/BRCA2 germline truncations were most prevalent in BRCA and OV, whereas IDH1 somatic variants are mostly found in AML, GBM and BLCA. Here, BRCA1 is linked to cancer.