SUN-LB102 Uncommon Pathology of Neck Mass

Poorly differentiated thyroid carcinoma (PDTC) is an uncommon form of thyroid cancer, accounting for less than 5 % of all cases. It tends to be more clinically aggressive than differentiated thyroid cancers. While thyroidectomy is the mainstay of treatment, radioactive iodine plays an adjunctive role as well as TSH suppression with thyroid hormone. Some patients with advanced disease, may benefit from external beam radiation and/or systemic therapy. Case Description: A 94-year-old man presents with a left neck mass. His past medical history is significant for controlled hypertension. He notices a slowly growing mass while shaving over few months. He has no dysphagia, hoarseness, or shortness of breath. He has no history of radiation exposure and no family history of thyroid disease. A CT of the neck with contrast shows multiple pathologic appearing lymph nodes on the left side of the neck. The largest measures 5.4 x 4 x 3.9 cm, displacing the carotid space, and indenting the left internal jugular vein. The left lobe of the thyroid is heterogeneously enlarged compared to the right lobe with multiple irregular hypo-enhancing nodules. A fine-needle aspiration of the left cervical lymph node is positive for malignant large cells in sheets and clusters. Some clusters have a vague papillary/trabecular type arrangement. A total thyroidectomy and left level II-IV neck dissection is performed. Pathology shows multifocal poorly differentiated papillary thyroid carcinoma measuring 2.2 cm in greatest dimension with extensive necrosis. There is a background of lymphocytic thyroiditis. There is extensive vascular invasion (>4 foci) and extra-thyroidal extension invading only the strap muscles. There is metastasis to 7 of 12 examined lymph nodes. The largest metastatic deposit at level III measures 2.8 cm with extra-nodal extension. Tumor is negative for BRAF-V600, NRAS and TERT. His postoperative labs are as follows: TSH 346 (post-rhTSH) uiu/ml (0.5-5.0), free T4 0.87 ng/dl (0.6-1.15),Tg 1.0 ng/ml and anti-Tg <0.9 iu/ml. Adjuvant therapy with 125 mCi of I-131 is performed as well as thyroid replacement with levothyroxine 100 mcg daily. A whole-body scan shows residual uptake in the thyroid bed and increased uptake to the left of the thyroid bed. FDG PET scan shows 2 left parapharyngeal nodes with SUV of 6.94 (0.8 cm), SUV of 3.73 (1.8 cm). There is a focus of increased activity at lateral left thyroid bed SUV of 4.59. There is a right mediastinal paratracheal lymph node with SUV of 9.79 measures 1.5 x 1.2 cm. Considering patient age, external beam radiation is deferred with patient agreement as the risk outweighs the benefit. Patient will be followed by imaging closely. Conclusion: PDTC is an uncommon form of thyroid cancer. These tumors generally do not produce thyroglobulin and close monitoring with imaging is essential to detect early metastatic disease. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.