This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tumors, Subject name: Pathology
Which of the following mutation is seen in Cowden syndrome? 
Select and explain. 
A. STK 11 mutation, B. SMAD 4 mutation, C. PTEN mutation, D. PTCH mutation
C: PTEN mutation
Answer: C: PTEN mutation 
Explanation: Mutation in PTEN gene: Breast tumors Endometrial tumors Skin appendage tumors Thyroid tumors Cowden syndrome: Dysplastic gangliogliocytoma of the cerebellum (Lhermitte Duclos disease), caused by mutations in PTEN resulting in PI3K/AKT signaling pathway PTEN