Peutz-Jeghers syndrome is caused by mutations in which gene, STK11, and which cancers are markedly increased?

• A. MSH2; colon and endometrial
• B. STK11; pancreatic, GI, sex-specific
• C. BRCA1; pancreatic, GI, sex-specific
• D. APC; colon and stomach

Answer: (B)

Peutz-Jeghers syndrome arises from germline mutations in STK11, also known as LKB1, a tumor suppressor that helps regulate cell growth and polarity. When STK11 is inactivated, individuals develop hamartomatous polyps in the GI tract and carry a markedly increased lifetime risk of cancer. The cancers most strongly associated with this syndrome are pancreatic cancer, various GI cancers (including stomach, small intestine, and colon), and sex-specific cancers such as breast cancer in women and certain gonadal tumors in men. This cancer pattern—pancreatic and GI tract cancers along with sex-specific tumors—is the hallmark linked to STK11-related Peutz-Jeghers.

Mutations in MSH2 are linked to Lynch syndrome with elevated risks for colon and endometrial cancers, not Peutz-Jeghers. BRCA1 mutations predispose mainly to breast and ovarian cancers (with some pancreatic risk) but do not define Peutz-Jeghers. APC mutations cause familial adenomatous polyposis with colon and other GI cancers, also not Peutz-Jeghers.