A Rare Clinical Encounter: Loculated Pleural Effusion in a Young Male With a History of Resected Cutaneous Melanoma.

Melanoma is known as one of the most aggressive types of malignant skin carcinoma. The development of melanoma is most commonly associated with excessive sun exposure, a family history of the disease, and genetic predisposition. Melanoma can metastasize to various anatomical sites; the lungs are a frequent site of metastatic involvement, and when pulmonary metastasis develops, respiratory failure becomes the leading cause of mortality. The predominant pathway of metastatic spread in primary cutaneous melanoma is through the regional lymph nodes. We report a case of a young male with a history of resected cutaneous melanoma one year prior to presentation, who developed gradually worsening shortness of breath and pleuritic chest pain over two weeks. An initial chest X-ray revealed a unilateral pleural effusion, and subsequent pleural tapping confirmed the presence of exudative fluid. Further evaluation with a chest CT scan demonstrated a left-sided loculated pleural effusion and a lobulated nodule with spiculated margins in the upper outer quadrant of the left breast, prompting additional evaluation via mammography and tissue biopsy. ‎Mammography revealed a dense, lobulated mass in the upper left breast, measuring 2 × 1.5 cm and located approximately 2.7 cm from the nipple. An ultrasound-guided biopsy of the lesion was performed. Histopathological analysis showed infiltrating large atypical cells and numerous pigmented cells. Immunostaining revealed positive staining for mesothelial cells (HBME-1) and a high proliferative index (Ki-67). Following pleural aspiration and gradual drainage of pleural fluid over several days, the patient exhibited marked clinical improvement. The case was referred to a tertiary care facility for further staging and comprehensive management. This case highlights the importance of maintaining a high index of suspicion for pleural metastatic melanoma in patients with a history of resected cutaneous melanoma.