A third case was a male presenting with metastatic rectal cancer at age 33, who harbored PSVs in BRCA1 and in MLH1. The tumor was found to display high microsatellite instability (MSI-H), and MMR immunohistochemistry staining on rectal tumor biopsy showed absence of MLH1 and PMS2 protein expression. The gene discussed is MRC1; the disease is rectal neoplasm.