A 39-year-old woman underwent right
colectomy for type-3 transverse colon
cancer, which was histologically identified as well-differentiated stage II A
adenocarcinoma with a mucinous component and tumor-infiltrating lymphocytes. The patient was suspected of having
Lynch syndrome(LS)since she fulfilled 2 of the revised Bethesda criteria, even though there was no family history of LS. Twelve months after
colectomy, abdominal CT revealed thickening of the uterine endometrium. Histopathological examination of biopsy specimens revealed well-differentiated
endometrioid carcinoma. Extended
hysterectomy with bilateral
oophorectomy was performed. Histological examination of the resected specimen revealed well-differentiated
endometrioid carcinoma of stage I . Immunohistochemistry analysis of mismatch repair
proteins demonstrated loss of MLH1/ PMS2 expression in the
colon cancer, but normal expression in the
uterine cancer. Genetic testing identified duplication of exons 10-15 of the MLH1 gene, leading to a definitive diagnosis of LS. The patient has not shown any evidence of recurrence or new LS-associated
tumors in the 12 years since the last surgery. There is an ongoing debate regarding the pathogenesis of endometrioid
cancer, and this case emphasizes the importance of surveillance for gynecological
malignancies after
colon cancer surgery in female LS patients.