SAT532 A Rare Case of Thyroid Carcinoma Noted in a Patient with Thyroid Nodule Showing Prior Benign Biopsy and Prior Negative Molecular Testing

Disclosure: M.M. Hillhouse: None. P. Madhavan: None. F.M. Woron: None. Background: Molecular studies have a high sensitivity for ruling out malignancy (1). This patient was diagnosed with the follicular variant of papillary thyroid carcinoma despite negative molecular testing and benign cytology in multiple prior biopsies. Clinical Case: 31 y.o. female with a past medical history of Hashimoto's disease on levothyroxine presented for follow up of thyroid nodules. She does not have a family history of thyroid cancer or personal history of neck radiation. The patient was noted to have a right thyroid nodule around 14 years of age and this was monitored during her childhood. The nodule measured 2.3 x 0.6 cm on ultrasound in 2015. The nodule measured 2.0 x 1.6 x 1.5 cm in 2017. FNA in 2017 revealed benign cytology (Bethesda II). On ultrasound in 03/2019, the nodule measured 2.2 x 1.5 x 1.8 cm. The nodule demonstrated a greater than 20% increase in all dimensions on ultrasound images in 12/2020 to 2.9 x 2.0 x 2.6 cm. A repeat ultrasound in 04/2021 demonstrated no significant change in size. Repeat FNA performed in 07/2021 demonstrated clusters of follicular cells in flat and microfollicular groups and was interpreted as atypia of undetermined significance (Bethesda III). AFIRMA testing was benign (∼4% of malignancy. The nodule increased in size to 3.5 x 2.6 x 3.1 cm on ultrasound in 07/2022. It appeared solid and hyperechoic and was classified as TI-RADS 3. A new 0.8 cm nodule on the left lobe was also identified. Repeat FNA of the right nodule in 09/2022 demonstrated macrophages, colloid and groups of follicular cells and was classified as non-diagnostic (Bethesda I). She reported difficulty breathing in the supine position and she underwent a right hemithyroidectomy and isthmusectomy in 11/2022. Pathology results were remarkable for invasive encapsulated follicular variant of papillary thyroid carcinoma with focal angioinvasion and tumor capsular invasion. The margins were negative for tumor. The parenchyma was consistent with lymphocytic thyroiditis. Ultrasound after interval right hemithyroidectomy in 12/2022 in an outside facility demonstrated an unchanged subcentimeter left thyroid nodule and multiple bilateral anterior cervical/level 6 lymph nodes suspicious for metastatic disease given the absence of hilum. Patient is currently undergoing repeat imaging and work up for the lymphadenopathy. Conclusion: This case study highlights the importance of maintaining high clinical suspicion for thyroid malignancy in cases of increasing thyroid nodule size and compressive symptoms despite negative cytological and molecular testing. References: (1) Kloos, R. Molecular Profiling of Thyroid Nodules: Current Role for the Afirma Gene Expression Classifier on Clinical Decision Making, Mol Imaging Radionucl Ther. 2017 Feb; 26(Suppl 1): 36-49. Presentation Date: Saturday, June 17, 2023