Background <p>Carotid body tumors are rare neuroendocrine tumors that typically present as benign masses. However, they can exhibit malignant transformation, especially when metastasis occurs, making them a significant challenge in diagnosis and management. This case report highlights the paradoxical nature of malignant carotid body tumors, where benign histological features can coexist with confirmed metastatic spread, emphasizing the critical need for careful evaluation and long-term follow-up.</p> Case presentation <p>We report the case of a 67-year-old Iranian woman who presented with a right-sided neck mass and vague, dull pain for 1 year. Imaging studies, including Doppler ultrasound, computed tomography, and magnetic resonance imaging, revealed a hypervascular mass at the right carotid bifurcation with the classic “salt-and-pepper” appearance. Surgical resection with selective neck lymphadenectomy was performed. Histopathological examination showed the classic Zellballen pattern with low mitotic activity. Immunohistochemistry confirmed the neuroendocrine origin, with strong positivity for chromogranin A, synaptophysin, and S100, and a low Ki-67 index. Importantly, one out of ten resected lymph nodes showed metastatic involvement, confirming the diagnosis of a malignant carotid body tumor.</p> Conclusion <p>This case underscores that malignancy in carotid body tumors is defined by the presence of metastases rather than histological appearance alone. It highlights the importance of maintaining high clinical suspicion, utilizing comprehensive diagnostic evaluations including imaging and thorough lymph node assessment, and implementing long-term follow-up for patients with carotid body tumors, even when initial histological findings seem benign. Such a multidisciplinary approach is crucial for improving treatment strategies and patient outcomes for these rare and unpredictable tumors.</p>