Synaptophysin Positive Pulmonary Glomus Tumor Mimics Carcinoid Tumor on Fine-Needle Aspiration

Glomus tumors are benign vascular soft tissue neoplasms of glomus bodies. Primary lung glomus tumors are rare and usually express smooth muscle markers, and are negative for cytokeratin and neuroendocrine markers in immunohistochemistry. We report a case of a primary lung glomus tumor showing diffuse, strong, aberrant immunoexpression for synaptophysin and morphologically mimicking a low-grade neuroendocrine tumor (carcinoid tumor).