SAT543 A Case of Non-iodine-Avid Papillary Thyroid Cancer With a Rare Distant Metastasis to the Pancreas

Disclosure: A.H. Alcain: None. M.C. Isidro: None. Papillary Thyroid Carcinoma is the most common type of differentiated thyroid cancer. Distant metastasis is rare occurring only in 5% of patients and typically involves the lungs and bones. Metastasis to the pancreas is extremely rare with few cases reported over the years. We present a case of a 65-year-old female, who presented with sudden onset of abdominal pain. A review of the patient’s medical history revealed a history of a non-iodine avid Papillary Thyroid Carcinoma in 2015. The patient underwent Radioactive Iodine (RAI) ablation therapy twice due to elevated Thyroglobulin (Tg) levels. Despite RAI, Tg levels were still elevated with no recurrence nor metastasis noted on scan. Chemotherapy was offered but the patient opted for Tomotherapy. The patient completed Tomotherapy in 2017 but afterward was lost to follow-up. A CT scan of the abdomen showed findings of a pancreatic tail and body mass (10 x 7 cm) with an invasion of the mid-descending colon with pulmonary nodules which are possibly metastatic. The patient underwent an endoscopic ultrasound-guided biopsy, and pathology showed findings of a pancreatic papillary neoplasm (CK and beta-catenin positive, synaptophysin negative). Chemotherapy was given (FOLFOX) and a PET scan was requested to monitor the response to treatment. However, PET-scan showed FDG-avid (SUV 32.1) mass in the pancreatic tail (7.2 x 7.8 x 13.3 cm), FDG-avid (SUV 17.61) nodules in the lungs, and an ill-defined heterogeneous mass in the left surgical site (2.2 x 2.6 x 5.3 cm). Given that patient had a thyroidectomy in 2015, recurrence was considered. The possibility of probable metastasis to the pancreas was entertained hence re-biopsy was done. Serum Tg levels were elevated (4,115 ng/ml NV: 1.59-50.0) and negative for Anti-Tg. Biopsy showed high-grade neoplasm with papillary features. IHC staining showed positive for CK7, Tg, and TTF-1, and negative for CK20 which was consistent with metastatic papillary thyroid carcinoma. The patient was given Lenvatinib and is at present tolerating the treatment well with evidence of decreasing Tg levels suggesting a response to treatment. This is a case of a rare site of distant metastasis of a non-iodine avid papillary thyroid carcinoma. Targeted therapy such as Tyrosine kinase inhibitors can improve the survival rate of patients with Radioiodine Refractory Thyroid cancers. Metastasis should be considered especially in patients with a history of prior malignancy. Presentation Date: Saturday, June 17, 2023