In contrast, patients suffering from heterozygous inactivating mutations of tumor suppressor genes, such as Familial Adenomatous Polyposis-FAP (APC), Seckel Syndrome (ATR), Blooms Syndrome (BLM), Familial Breast or Ovarian Cancer Syndrome (BRCA1/BRCA2), Lynch Syndrome (MLH1/MSH2), Neurofibromatosis Type 1 (NF1), Familial Retinoblastoma (RB), and Li-Fraumeni Syndrome (TRP53) are expected to be at particular risk. This evidence concerns the gene MLH1 and microcephalic primordial dwarfism.