Primary malignant melanoma of the lung: a case report and literature review

BACKGROUND: Malignant melanoma (MM) generally presents as a primary neoplasm of the skin, and most MM cases of the respiratory system are metastatic. Primary MM of the lung (PMML) is quite rare, and its diagnosis is relatively difficult. CASE PRESENTATION: We report the case of a 57-year-old male patient with PMML who denied any history of tumours. His initial complaint was frequent coughs with bloody sputum for 4 days. Chest radiography demonstrated a high-density shadow in the lower lobe of the right lung, which was suspected to be a large space-occupying lesion on subsequent computed tomography (CT) and to be a hypermetabolic tumour by positron emission tomography–CT. To confirm the diagnosis, exploratory surgery was performed. Finally, we confirmed the diagnosis of PMML. CONCLUSIONS: PMML is extremely rare and easily misdiagnosed as lung cancer. Because of its morphological and immunophenotypic variations, the diagnosis of PMML remains difficult. This case report discusses the diagnosis and case management of a patient while referring to the existing literature.