The clinical features, treatment, and prognosis of primary mediastinal malignant melanoma: A case report.

Rationale: Primary malignant melanoma (MM) of the mediastinum is exceedingly rare; a review of the English-language literature reveals only a small number of case reports. In this paper, we discuss a case of primary mediastinal MM and present a review of the relevant literature on its clinical features and treatment.
Patient Concerns: A 52-year-old male presenting with back pain was admitted to our hospital for treatment. Imaging examination revealed an anterior mediastinal mass and no evidence of other metastatic or primary lesions.
Diagnoses: After complete resection by video-assisted thoracoscopic surgery (VATS), histopathologic examination showed evidence of brown melanin pigment in the tumor cells, which were immunohistochemically positive for antimelanoma antibodies (HMB-45, Melan-A, S-100, and Ki67).
Interventions: Given the diagnosis of MM after surgery, the tumor was tested for the mutation in the BRAF gene (which encodes the serine/threonine-protein kinase B-raf) that leads to a V600E amino acid substitution, and the tumor was found to be wild type. Then the patient has been given immunotherapy.
Outcomes: The patient completed 4 cycles of immunotherapy, and no recurrence or metastasis has been detected to date.
Lessons: In such cases, it is difficult to prove the primary nature of the intrathoracic melanoma. Moreover, preoperative identification of this disease is challenging, making misdiagnosis likely. Due to fast progression and poor prognosis, timely and effective systemic treatment is necessary to improve the outcomes for patients with primary mediastinal MM.