(B) PTENo"Phosphatase and Tensin'' homolog (PTEN) - protein in humans encoded by the PTEN gene. Gene mutations promotes development of cancers.[?]Cowden's disease/Multiple Hamartoma Syndrome:-Part of PTEN hamartoma tumor syndrome-An autosomal dominant syndrome-Trichilemmomas - Numerous tumors of hair follicles in face-Multiple hamartomatous polyps in GI tract, Lipomas, Granulomas-Very high risk of breast, Follicular endometrail carcinoma & thyroid carcinomaoTreatment: Bilateral mastectomies recommended-Contraindicated are mammography & other radiation exposure of breast tissue.-Mean age at presentation <10 years-Very high risk of breast, follicular carcinoma of thyroid & Endometrial carcinomaoPTEN (phosphatase and tensin homologue) is a membrane-associated phosphatase encoded by a gene on chromosome 10q23 that is mutated in Cowden syndrome, an autosomal dominant disorder marked by frequent benign growths, such as skin appendage tumors, and an increased incidence of epithelial cancers, particularly of the breast, endometrium, and thyroid.oPTEN acts as a tumor suppressor by serving as a brake on the PI3K/AKT arm of the receptor tyrosine kinase pathway.oPTEN gene function is lost in many cancers through deletion, deleterious point mutations, or epigenetic silencing.SELECTED TUMOR SUPPRESSOR GENES & ASSOCIATED FAMILIAL SYNDROMES & CANCERS, SORTED BY CANCER HALLMARKS*Gene (Protein)Familial SyndromesAssociated CancersInhibitors of Mitogenic Signaling PathwaysAPC (Adenomatous polyposis coli protein)Familial colonic polyps and carcinomasCarcinomas of stomach, colon, pancreas; melanoma*. NF1 (Neurofibromin-1)Neurofibromatosis type 1 (neurofibromas and malignant peripheral nerve sheath tumors)Neuroblastoma, juvenile myeloid leukemia*. NF2 (Merlin)Neurofibromatosis type 2 (acoustic schwannoma and meningioma)Schwannoma, meningioma*. PTCH (Patched)Gorlin syndrome (basal cell carcinoma, medulloblastoma, several benign tumors)Basal cell carcinoma, medulloblastoma*. PTEN (Phosphatase and tension homologue)Cowden syndrome (variety of benign skin, GI, and CNS growths; breast, endometrial, and thyroid carcinoma)Diverse cancers, particularly carcinomas and lymphoid tumors*. SMAD2, SMAD4 (SMAD2, SMAD4)Juvenile polyposisFrequently mutated (along with other components of TGFb signaling pathway) in colonic & pancreatic CaInhibitors of Ceil Cycle Progression*. RB Retinoblastoma (RB) proteinFamilial retinoblastoma syndrome (retinoblastoma, osteosarcoma, other sarcomas)Retinoblastoma; osteosarcoma carcinomas of breast, colon, lung*. CDKN2A p16/INK4a & pU/ARFFamilial melanomaPancreatic, breast, and esophageal carcinoma, melanoma, certain leukemiasInhibitors of "Pro-growth" Programs of Metabolism and Angiogenesis*. VHL (Von Hippel Lindau (VHL) protein)Von Hippel Lindau syndrome (cerebellar hemangioblastoma, retinal angioma, renal cell carcinoma)Renal cell carcinoma*. STK11 (Liver kinase B1 (LKB1) or STK11)Peutz-Jeghers syndrome (GI polyps, GI cancers, pancreatic carcinoma and other carcinomas)Diverse carcinomas (5%-20% of cases, depending on type)*. SDHB, SDHD (Succinate dehydrogenase complex subunits B & D)Familial paraganglioma, familial pheochromocytomaParaganglioma