Alveolar Rhabdomyosarcoma: An Unusual Presentation

Abstract

Rhabdomyosarcoma is a primitive malignant round blue cell tumor with skeletal muscle differentiation. Alveolar rhabdomyosarcoma typically affects the extremities and manifests as a painful soft tissue mass or swelling. Other common locations affected by alveolar rhabdomyosarcoma include the perirectal and perineal regions, head and neck, and genitourinary system. We present a case of an 18-year-old woman with no significant medical history who had the chief complaint of a 2-week history of worsening shortness of breath. Chest x-ray revealed a significant pleural effusion encompassing her entire right lung cavity. A chest tube was inserted, and pleural fluid was sent for cytology. Single and clustered poorly differentiated malignant cells were identified. The morphologic, immunocytochemical, and electron microscopic results supported skeletal muscle differentiation consistent with rhabdomyosarcoma. CT scans showed right pleural thickening, well-circumscribed peripheral right lung nodules, mediastinal lymphadenopathy, and possible chest wall invasion. A thoracoscopy revealed that the entire right parietal pleura was studded with white tumor excrescences. A pleural biopsy was performed. The morphologic, immunohistochemical, and cytogenetic results confirmed the diagnosis of alveolar rhabdomyosarcoma. The pleural effusion, lack of a discrete mass, and unusual location of the tumor make this a unique manifestation of alveolar rhabdomyosarcoma diagnosed by cytopathology. Category:Cytopathology