A 42-year-old female patient has a malignancy involving the vestibule of her vagina. Which are the first lymph nodes to filter the lymph drainage from this area and therefore the most likely to become involved in tumor spread?

The superficial inguinal nodes drain superficial perineal structures, including the superolateral uterine body near attachment of the round ligament, skin of the perineum (including the vulva), and the introitus of the vagina inferior to the hymen. The internal iliac nodes drain the middle and upper vagina, cervix, and body of the uterus. The lumbar/lateral aortic lymph nodes drain the ovaries. The axillary lymph nodes drain the upper limb and chest wall, including the breast.