Metastatic Carotid Body Paraganglioma Following Three Decades of Indolent Growth: A Case Report.

Paragangliomas (PGLs) are rare neuroendocrine tumors arising from extra-adrenal chromaffin cells, with head and neck paragangliomas (HNPGLs) accounting for only a small proportion of all cases. Although most HNPGLs are benign, slow-growing, and nonfunctional, a minority develop metastatic disease, for which reliable histopathologic predictors remain lacking. We report the case of a 63-year-old man who presented with a progressively enlarging left-sided neck mass that had been present for more than 30 years before evaluation. Imaging demonstrated a carotid body paraganglioma with cervical lymph node involvement and distant suspected metastases to the thoracic and lumbar spine, lung, salivary gland, shoulder soft tissue, and small bowel. Histopathology confirmed paraganglioma with classic Zellballen architecture and positive staining for synaptophysin, chromogranin-A, CD56, GATA3, and S100-positive sustentacular cells. Given the patient's minimal symptoms despite extensive metastatic disease, a multidisciplinary team initially pursued active surveillance with serial multimodal imaging. Radiographic progression over time prompted initiation of systemic therapy with cabozantinib, which resulted in decreased metabolic activity of the primary tumor and no fluorodeoxyglucose-avid evidence of metastatic disease on follow-up imaging. This case highlights the unpredictable biological behavior of carotid body paragangliomas, demonstrating that longstanding, minimally symptomatic tumors may ultimately progress to widespread metastatic disease. It further emphasizes the importance of prolonged surveillance, multimodal imaging, multidisciplinary management, and individualized treatment strategies for patients with metastatic HNPGLs in the absence of reliable predictors of malignant potential.