Primary Mediastinal Malignant Melanoma Presenting With Pleural Effusion: A Case Report

BACKGROUND: Primary mediastinal malignant melanoma (PMMM) presenting with pleural effusion as the initial manifestation is exceedingly rare, presenting significant diagnostic and therapeutic challenges. This article reports a case of PMMM that initially manifested as pleural effusion and includes a review of the relevant literature. CASE: The patient was admitted with pleural effusion and an anterior mediastinal mass. A pleural biopsy and fine-needle aspiration of the mediastinal mass led to a pathological diagnosis of malignant melanoma. Ultimately, based on clinical findings, a final diagnosis of PMMM was established. The patient subsequently developed pleural hemorrhage; although hemostasis was achieved through thoracoscopy, his condition stabilized only temporarily. He ultimately succumbed to lung infection and multiple organ failure. CONCLUSION: PMMM presenting with pleural effusion lacks distinct clinical features, highlighting the importance of pathological diagnosis. Pleural hemorrhage associated with pleural metastasis may be a characteristic feature, and the prognosis for such cases is poor. Enhanced recognition and early intervention are essential to improve outcomes.