MON-319 A Rare Case of SDHB mutation related Paraganglionoma and Papillary Thyroid Cancer

Abstract Disclosure: B. Singh: None. S. Samarasinghe: None. Paragangliomas (PGL) are rare endocrine tumors with approximately 500-1000 cases diagnosed annually. The germline mutation at the succinate dehydrogenase subunit-B gene (SDHB) has a prevalence of approximately 5% of hereditary PGLs with a more locally aggressive disease course and 30% rate of recurrence. In addition to PGLs, 1-5% of patients with SDHB mutation can be diagnosed with concomitant papillary thyroid cancer (PTC). We present a rare case of a patient diagnosed with retroperitoneal PGL and PTC found to have a germline SDHB mutation. This is a case of a 33-year-old female without significant past medical history presented for evaluation of a left sided cervical mass. An ultrasound revealed a soft tissue mass lateral to the left lobe of the thyroid measuring 3.6 x 1.4 x 2.3 cm. An FNA was advised, however the patient traveled abroad to undergo the biopsy. This procedure was complicated by hypertensive urgency and aborted. She returned with laboratory evaluation demonstrating markedly elevated plasma normetanephrines, urine norepinephrine and total catecholamines. A CT chest/abdomen showed a retroperitoneal mass measuring 3.6 x 2.5 x 4.1 cm consistent with a retroperitoneal PGL. An MIBG scan was negative for additional extra-adrenal PGL. She underwent surgical excision with pathology confirming a 4.7 cm paraganglioma with negative margins. Two months later, she underwent excision of the left carotid sheath mass which revealed a lymph node consistent with metastatic PTC. She then underwent total thyroidectomy with central cervical lymph node dissection. Pathology was significant for a 0.6 cm foci of follicular variant PTC with 4/4 lymph nodes positive for metastatic disease (largest 1.5 cm) with pathologic staging pT1a, N1b. She completed radioactive iodine ablation with a post therapy whole body scan negative for local or distant uptake. Given the finding of a retroperitoneal paraganglioma, the patient underwent genetic testing and was found to have a germline mutation c.7301G>A in the SDHB gene. She is being monitored with annual plasma metanephrines, MRI of the skull base, neck, abdomen and pelvis every 3-5 years, MRI of the chest every 5 years and DOTATATE PET CT every 5 years at appropriate intervals. This case report contributes to the evolving understanding of SDHB germline mutation linked syndromes. Although genetic testing is routinely performed for PGLs, there are very few cases reporting concurrent metastasized PTC and PGL in known SDHB mutation carriers. It is well known that SDHB mutations can lead to extraparaganglial cancer. However, there are only a few reported studies to correlate this mutation to more aggressive forms of PTC. Further research is required to assess the prevalence of PTC in known SDHB mutation carriers and how the presence of this germline mutation influences the disease course of patients with PTC. Presentation: Monday, July 14, 2025