Early Postoperative Recurrence and Systemic Metastases Following Curative Resection of Primary Melanoma of the Lung

Primary melanoma of the lung (PML) is exceedingly rare, accounting for approximately 0.01% of lung cancers. Because cutaneous melanoma may undergo spontaneous regression, a solitary pulmonary melanoma may represent either a true primary lesion or a metastasis from an occult regressed cutaneous primary. Therefore, rigorous exclusion of extrapulmonary primary sites is essential. PML is generally associated with a poor prognosis, and its biology and optimal management remain incompletely defined. Here, we report a case of PML with early systemic relapse after curative resection and provide a brief review of the literature.

A 57-year-old woman was referred to our department (Department of General Thoracic Surgery, Osaka International Cancer Institute) for surgical management after an abnormal chest shadow was detected on routine health screening. Chest CT revealed a 2.0-cm irregular nodule in the left lower lobe with ipsilateral hilar lymphadenopathy. ¹⁸F-fluorodeoxyglucose (FDG)-PET/CT showed uptake in both lesions without evidence of disease elsewhere. Initial bronchoscopic biopsy at the referring hospital suggested a neuroendocrine tumor, whereas repeat bronchoscopic sampling at our institution raised suspicion for melanoma. Detailed dermatologic examination found no suspicious cutaneous lesions. The patient underwent open left pneumonectomy with regional lymphadenectomy; final pathology confirmed PML. Adjuvant pembrolizumab was initiated 1 month after surgery. At 4 months postoperatively, FDG-PET/CT demonstrated recurrence at the bronchial stump, mediastinal lymph nodes, pleural dissemination, and multiple systemic metastases. Combination therapy with nivolumab plus ipilimumab was administered; however, the disease progressed, and the patient died of disease 8 months after surgery.

This case highlights the diagnostic challenges and aggressive clinical course of PML. Thorough exclusion of extrapulmonary primary sites and comprehensive histopathologic and molecular assessment are required. Given the high risk of early systemic relapse, further investigation of multidisciplinary strategies, including perioperative systemic therapy, is warranted.