Carbon ion radiotherapy for vaginal malignant melanoma: a case report

Malignant melanoma of the vagina is a very rare neoplasm and resistant to conventional radiotherapy. We report a case of vaginal malignant melanoma that was locally well controlled by carbon ion radiotherapy. A 55-year-old postmenopausal woman presented with abnormal vaginal bleeding. On pelvic and imaging examinations, an irregular mass of the posterior vaginal wall sized 7.5 x 5 x 5 cm, an enlarged right inguinal lymph node, and two lung metastases were observed. Histologic diagnosis based on positive immunostaining for HMB-45 was malignant melanoma. She received dacarbazine-based chemotherapy and carbon ion radiotherapy for vaginal and inguinal tumor sites with 57.6 Gy equivalent dose per 16 fractions using five ports. Six months later, she was also given carbon ion radiotherapy for regrowing lung metastasis with 52.8 Gy equivalent dose per four fractions using four ports. She died 19 months after initial treatment due to brain metastases. The primary irradiated tumor disappeared completely 12 months after initial treatment. The vaginal tumor, right inguinal lymph node, and lung tumor treated with carbon ion radiotherapy did not show any evidence of recurrence until her death. Carbon ion radiotherapy may be of value for vaginal malignant melanoma as a conservative approach.