While in a first moment it was suggested that each different type of cancer was related to one or a few specific genes (e.g., BRCA1/2 for BC and OC, APC for familial adenomatous polyposis, etc.), our study revealed that often there is not correspondence between tumor type and the associated mutated gene, raising the question about the need for more genes to be analyzed in hereditary cancers. The gene discussed is BRCA1; the disease is Familial adenomatous polyposis.