Clinicopathologic significance of DNA mismatch repair protein defects and endometrial cancer in women 40years of age and younger.

Background: The hereditary basis of endometrial cancer is apparent in young women with endometrial cancer. The objective of this study was to examine risk factors and outcomes in patients 40 years of age and younger with endometrial cancer.

Methods: We performed a retrospective cohort study of patients aged 40 years or less who were diagnosed with endometrial carcinoma between 1/93 and 5/08. Clinical and pathologic data were extracted from medical records. Paraffin-embedded slides from hysterectomy specimens were obtained and DNA mismatch repair (MMR) immunohistochemistry was performed. Cases were analyzed according to the presence of DNA MMR protein defects. Standard two-sided statistical tests were performed.

Results: Of the 56 identified patients, the median age was 36 years (range, 24-40). The majority of the endometrial carcinomas were of endometrioid histology (91%), stage I (71%), and FIGO grade 1 (59%). Abnormal DNA MMR was found in 9 cases (16%). Cases with abnormal DNA MMR had lower body mass index (BMI) (P=0.05), and had a family history suggestive of Lynch syndrome (P=0.001). Tumors were more likely to have advanced stage disease (P<0.001), be high grade (P<0.001), have deep myometrial invasion (P<0.001), and have lymphovascular invasion (P=0.002). Cases with abnormal DNA MMR had significantly worse overall survival (P=0.028) and progression-free survival (P=0.042).

Conclusions: Endometrial cancer is rare in women aged 40 years or less. In this group of patients, loss of DNA MMR was associated with lower BMI, worse clinicopathologic factors, and worse outcome. These results may have implications when young women diagnosed with endometrial cancer are counseled regarding prognosis.