CRA62 THE INTERNIST’S TUMOUR IN DISGUISE: A CASE SERIES OF RENAL CELL CARCINOMA PRESENTING AS MALIGNANT PLEURAL EFFUSION

Fui Bee Woo¹, Nai-Chien Huan²

¹Respiratory Unit, Department of Internal Medicine, Hospital Tuanku Ja’afar, Negeri Sembilan, Malaysia
²Department of Respiratory Medicine, Hospital Queen Elizabeth, Sabah, Malaysia

Introduction
Renal cell carcinoma (RCC), often referred to as the "internist’s tumour," commonly presents with systemic manifestations rather than classic urological symptoms. The traditional triad—flank pain, haematuria, and a palpable flank mass—is infrequently seen. RCC is a rare cause of malignant pleural effusion (MPE), accounting for only 1–2% of cases, and isolated presentation with pleural effusion is uncommon. This case series describes three patients with RCC who initially presented with massive pleural effusion as the sole clinical manifestation.

Case presentation
All three patients presented with cough, dyspnoea, and/or fever. Notably, none reported flank pain or haematuria. Chest radiographs revealed massive pleural effusion. Thoracentesis in all cases showed exudative effusion with negative cytology. Definite diagnoses were obtained via medical thoracoscopy in all cases. Subsequent histopathological and radiological assessment confirmed metastatic renal cell carcinoma as the primary source. Due to the aggressive nature of the disease, none of the patients were candidates for surgical resection at the time of diagnosis, and all experienced rapid clinical decline within one year of initial diagnosis.

Discussion
Pleural involvement in RCC is hypothesised to occur via lymphatic or hematogenous dissemination. It typically presents as a late manifestation of the disease and is associated with poor prognosis. Early identification of pleural metastasis may enable the timely initiation of molecular targeted therapies, potentially improving patient outcomes.