Renal Cell Carcinoma Presenting As Isolated Malignant Pleural Effusion: A Case Report.

Renal cell carcinoma (RCC) of the clear cell type is the most common form of renal malignancy. Malignant pleural effusion (MPE) as the initial presentation of RCC is very rare. This case report presents a case of RCC that initially manifested as a pleural effusion, without the typical symptoms of flank pain, hematuria, or a palpable abdominal mass. The patient, a 45-year-old male, arrived with complaints of dyspnea and a dry cough, with no notable medical history or risk factors. Imaging revealed a left-sided pleural effusion, which was identified as MPE based on pleural fluid analysis, cytology, and immunohistochemistry. Subsequent investigation revealed a large, solid cystic mass in the left kidney, with a biopsy confirming RCC. Uniquely, the patient exhibited pleural metastasis without involvement of the lung parenchyma, a rare scenario in RCC that is linked to a poor prognosis. This case emphasizes the variable presentation of RCC and the need to consider malignancy in patients with unexplained pleural effusion. An indwelling pleural catheter was placed for the patient considering the poor prognosis; furthermore, he declined to undergo sessions of palliative chemotherapy and was subsequently lost to follow-up.