Robot-assisted laparoscopic hepatectomy for liver metastasis from clitoral malignant melanoma: a case report

Introduction: Malignant melanomas occur most commonly in the skin, mucous membranes, or choroid. Clitoral malignant melanomas are extremely rare. Stage IV malignant melanomas have a poor prognosis, and molecularly targeted agents or immune checkpoint inhibitors are recommended. However, surgical resection is reportedly a valid option for improving the prognosis of patients with oligometastases, defined as a small number of metastases that can be completely resected. In this report, we describe hepatic resection for a recurrent liver metastasis in a patient who had undergone removal of a clitoral malignant melanoma 9 years previously.

Case presentation: An 82 year-old woman presented with a black nodule on her clitoris. Total resection of the nodule resulted in a diagnosis of clitoral malignant melanoma (pT4bN0M0, pStage IIC; UICC 8th edition). A follow-up computed tomography scan 4 years later revealed a single 5 mm mass in the lower lobe of the right lung, prompting partial resection of the right lung. Pathological examination of the operative specimen revealed a pulmonary metastasis of malignant melanoma. The patient was treated with pembrolizumab monotherapy as adjuvant chemotherapy for 1 year. A follow-up computed tomography scan 9 years after surgical removal of the primary lesion revealed an 18 mm mass in segment II of the liver, prompting robot-assisted laparoscopic left lateral sectionectomy. The provisional diagnosis of metastatic malignant melanoma in the liver was confirmed by histopathological examination of the operative specimen. The patient was treated with pembrolizumab monotherapy as postoperative adjuvant chemotherapy for 1 year. No further recurrence was detected at the 1.5 year follow-up.

Conclusion: We performed hepatectomy for oligometastasis of clitoral malignant melanoma, an extremely rare entity. Surgery has the potential to prolong the prognosis of patients with oligometastasis.