This phenotype of the brothers is unusual as they neither develop hematological malignancies nor brain tumors at an older age of presentation than other patients with homozygous MSH2 mutations.
A possible association of hematologic malignancy with hereditary nonpolyposis colon cancer reported in the literature, together with a report that MSH2-deficient mice are susceptible to malignant lymphoma, strongly supports the finding that this patient's lymphoma was related to hereditary nonpolyposis colon cancer.