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. This evidence concerns the gene BRCA1 and bladder transitional cell carcinoma.