In utero exposure to diethylstilbestrol (DES) has been identified as a risk factor for which cancer?

• A. Vaginal cancer
• B. Cervical cancer
• C. Ovarian cancer
• D. Endometrial cancer

Answer: (A)

Exposure to DES in the womb is a well-known cause of abnormal development of the female reproductive tract, and the most specific cancer linked to that exposure is vaginal cancer, particularly the clear cell adenocarcinoma type. DES, used in the past to prevent miscarriage, has estrogen-like effects that disrupt normal development of the vaginal and Müllerian tissues, leading to changes such as vaginal adenosis and, when malignant transformation occurs, clear cell carcinoma of the vagina. This association is much stronger for vaginal cancer than for other gynecologic cancers. Cervical cancer is primarily linked to HPV infection; endometrial and ovarian cancers have different risk profiles and are not strongly tied to DES exposure.