Osteosarcoma presenting with massive malignant pleural effusion

Osteosarcoma is an aggressive primary bone tumor arising from primitive bone-forming cells. The most frequent site of metastasis is the lung followed by bone. However, osteosarcoma presenting as malignant pleural effusion during the initial presentation is extremely rare. Involvement of more than one bone at the time of initial presentation is rare and it is confusing whether these multiple lesions represent multiple primaries or metastasis. We report the case of a 17-year-old male who presented with fever and breathlessness of 1-month duration. Examination revealed massive pleural effusion. Pleural fluid cytology showed malignant cells. On examination, a scalp swelling was also noted. Radiological evaluation revealed multiple bony lesions involving the skull, femur, humerus, and vertebrae. Biopsy of the lesion in the humerus confirmed the diagnosis of osteosarcoma.