Primitive neuroectodermal tumor of the lung

Primitive neuroectodermal tumors occur most frequently in bone and soft tis sue but have been reported in other locations. Primary lung primitive neuro ectodermal tumors without pleural or chest wall involvement are extremely r are. 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 sho wed an endobronchial tumor. The lesion was resected by middle lobectomy. Af ter 2 years, a local recurrence was treated by pneumonectomy. The patient d ied after surgery. Histologically, the tumor was composed of uniform cells with round nuclei and scanty cytoplasm arranged in cohesive lobules with oc casional rosette formation. Immunohistochemically, the tumor was positive f or vimentin, CD99, neuron-specific enolase, and neurofilaments. Ultrastruct ural 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.