Primitive neuroectodermal tumor of the lung.

Primitive neuroectodermal tumors occur most frequently in bone and soft tissue but have been reported in other locations. Primary lung primitive neuroectodermal tumors without pleural or chest wall involvement are extremely rare. We present a case with immunohistochemical and ultrastructural studies and follow-up of the patient. An 18-year-old man presented with hemoptysis. Chest radiographs revealed a right middle lobe mass, and bronchoscopy showed an endobronchial tumor. The lesion was resected by middle lobectomy. After 2 years, a local recurrence was treated by pneumonectomy. The patient died after surgery. Histologically, the tumor was composed of uniform cells with round nuclei and scanty cytoplasm arranged in cohesive lobules with occasional rosette formation. Immunohistochemically, the tumor was positive for vimentin, CD99, neuron-specific enolase, and neurofilaments. Ultrastructural study revealed neurosecretory granules and cytoplasmic processes. Our case shows the value of immunohistochemistry and electron microscopy in the diagnosis of primitive neuroectodermal tumors in unusual locations.