Synchronous Bilateral Shamblin Type III Carotid Body Tumors and Adrenal Pheochromocytoma with SDHD Mutation: A Rare Presentation, with Multimodality Imaging Findings.

Pheochromocytomas and paragangliomas are relatively rare tumors, with an incidence of approximately 0.6 cases per 100,000 person-years. Moreover, the co-occurrence of these tumors is extremely rare and is often associated with pheochromocytomas/paragangliomas-related pathogenic mutations. We present the case of a 33-year-old female diagnosed with bilateral carotid body paragangliomas and a concurrently detected pheochromocytoma, with metastases to the abdominal lymph nodes and lung. DNA analysis revealed a mutation in the succinate dehydrogenase subunit D gene. The tumors displayed high-grade SSTR expression (Krenning grade 4 uptake) on Gallium-68 [⁶⁸Ga]-DOTA-(Tyr 3 )-octreotate Positron Emission Tomography/Computed Tomography, with no significant tracer concentration on the I-131 MIBG scan. Another notable feature in this case was the visually evident intra- and inter-tumoral metabolic heterogeneity on 18 F-fluorodeoxyglucose positron emission tomography/computed tomography, especially within the multiple carotid paragangliomas. With the adoption of a multimodality diagnostic approach (MRI, FDG PET/CT, SSTR PET/CT, and I-131 MIBG scintigraphy), a holistic theranostic approach was employed with the most rational therapeutic option offered to the patient.