Clinical significance of mismatch repair genes immunohistochemical expression of complex endometrial hyperplasia

OBJECTIVE Women with Lynch syndrome have an increased risk of developing colorectal and gynecologic malignancies such as endometrial cancer. Complex hyperplasia has about a 30% risk of developing into endometrial cancer. The aim of this study was to determine the genetic risk for developing endometrial cancer by immunohistochemical staining of premalignant lesions for mutL homolog 1, mutS homolog 2, mutS homolog 6, and postmeiotic segregation increased 2. METHODS Twenty cases (n=20) were selected from among patients with available sample blocks for analysis. Clinical information was obtained from medical chart review. Immunohistochemical staining was performed for all of the tumor blocks. Staining was scored based on the intensity (intensity score 0-3) . RESULTS Among the 20 cases of complex endometrial hyperplasia, 11 (55%) patients showed loss of expression of at least one of the following proteins: mutL homolog 1, mutS homolog 2, mutS homolog 6, or postmeiotic segregation increased 2. Seven (35%) patients were negative for the expression of two or more proteins, and one patient (5%) was negative for the expression of all four proteins. CONCLUSION More than half of the patients showed loss of expression of at least one mismatch repair protein in our study population. Genetic risk counseling and further tests are recommended for these patients.