Embryonal Rhabdomyosarcoma of The Lung: A Common Tumor with Atypical Primary Site

Introduction: Embryonal rhabdomyosarcoma is the commonest type of rhabdomyosarcoma in children. Its common primary sites include but not limited to head and neck, genitourinary, and extremities. However, embryonal primary pulmonary rhabdomyosarcoma is extremely rare. Case presentation: Our patient, 5 years old male presented with a four-week history of progressive worsening shortness of breath. The patient also had previous history of recurrent pneumonitis. On imaging, contrast enhanced chest CT demonstrated 16.1 x 13.1 x 13.3cm predominantly cystic mass with solid component on the right hemithorax. Metastatic workup was none revealing. Hence, open thoracotomy was done to cut out the mass, and sample was sent for histopathologic and immunohistochemistry assessment. Microscopy revealed pleomorphic round to oval to spindle blue cells in myxoid stroma along with anaplastic cells. Furthermore, the cells immunohistochemically reacted positively for smooth muscle actin, myogenin, and vimentin. Hence, the mass was confirmed to be embryonic type rhabdomyosarcoma of the lung. Accordingly, chemotherapy commenced, and he was given three cycles. Unfortunately, the patient died after three months. This case underscores the importance of suspecting primary pulmonary rhabdomyosarcoma in patients with recurrent bouts of pneumonic symptoms. Moreover, primary pulmonary rhabdomyosarcoma should be part of the differential diagnosis for lung mass with mixed components (cystic and solid). Conclusion: Finally, embryonic rhabdomyosarcoma showing anaplastic cells tends to have unfavorable prognosis.