Disseminated neuroendocrine carcinoma in a pediatric patient: a rare case and diagnostic challenge.

A previously healthy 16-year-old female presented with 1-month history of fever, cough, extremity pain, left upper quadrant pain, and night sweats. Imaging studies revealed mediastinal lymphadenopathy, lung and liver masses, and bony lesions. Liver and bone marrow biopsies revealed small tumor cells with a high nuclear cytoplasmic ratio, stippled chromatin, and inconspicuous nucleoli surrounded by bands of collagen. Immunohistochemically, the tumor cells were positive for epithelial (epithelial membrane antigen and cytokeratin AE1/AE3) and neuroendocrine markers (chromogranin and synaptophysin), and negative for other antigens tested, including vimentin, desmin, CD99, and WT-1. The morphologic features and immunohistochemical profile was consistent with neuroendocrine carcinoma. Despite several chemotherapeutic regimens, the patient had progressive disease and enrolled in a phase 1 trial. Thorough histopathologic evaluation, including immunohistochemical stains is a crucial component for diagnosing this rare, aggressive tumor in children and adolescents.