This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neoplasia, Subject name: Pathology
Which of the following mutation seen in Cowden syndrome? 
Select and explain. 
A. PTCH mutation, B. PTEN mutation, C. STK11 mutation, D. SMAD4 mutation
B: PTEN mutation
Answer: B: PTEN mutation 
Explanation: Ans. b. PTEN mutationRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No-291Tumor suppressor genes and associated with syndromesGeneProteinFunctionFamilial syndromesPTCHPatchedInhibitor of Hedgehog signalingGorlin syndrome (basal cell carcinoma, medulloblastoma, several benign tumors)PTENPhosphatase and tensin homologueInhibitor of PI3K/AKT signalingCowden syndrome (variety of benign skin, Gl, and CNS growths; breast, endometrial, and thyroid carcinoma)STK11Liver kinase B1 (LKB1) or STK11Activator of AMPK family of kinases; suppresses cell growth when cell nutrient and energy levels are lowPeutz-Jeghers syndrome (Gl polyps, Gl cancers, pancreatic carcinoma and other carcinomas)SMAD4SMAD4Component of the TGFP signaling pathway, repressors of MYC and CDK4 expression, inducers of CDK inhibitor expressionJuvenile polyposis, pancreatic carcinoma