SAT544 Abnormal Labs Reveal Metastatic Papillary Thyroid Cancer

Disclosure: M. Shahid: None. S. Bellamy: None. A. Ottley: None. M. Griffith: None. Objective:Abnormal thyroid function studies are commonly referred to Endocrinology for further evaluation. In most cases, once studies are repeated and normal no further work up is considered. It is uncommon to order a thyroid ultrasound if the patient is asymptomatic with repeat normal labs and physical exam. Clinical Case:43 yo female with no significant medical history who presented to Endocrine clinic for evaluation of abnormal thyroid function labs. She denied taking any medications. Review of systems was positive only for a five pound weight gain over three months. Her physical exam was unremarkable. Labs were significant for TSH level of 0.25 uIU/mL (normal range 0.45 - 5.33 uIU/mL), free T4 of 0.57 ng/dL (normal range 0.61 - 1.12 ng/dL). At the initial visit, thyroid function tests, thyroid antibodies, and thyroid ultrasound were ordered. Results included a normal serum TSH , Free T4 and Thyroid Stimulating Immunoglobulin. Thyroid Peroxidase Antibody resulted as detectable at 124 IU/mL (normal value <9 IU/mL). Thyroid ultrasound showed nodules bilaterally; some subcentimeter in size with two meeting criteria for FNA; one in the right mid pole measuring up to 1.8 cm with suspicious features of hypoechogenicity and a feeding blood vessel, and another isoechoic left mid pole nodule measuring up to 1.8 cm. Per pathology, the right mid pole nodule was considered Betheseda Category V, suspicious for Hurtle cell neoplasm or Hashimoto’s thyroiditis, with the possibility of medullary or papillary thyroid carcinoma. The left mid pole nodule was considered Bethesda Category II. Following surgical consultation, the patient underwent total thyroidectomy with right cervical neck dissection. Pathology revealed pT3N1Mx Metastatic Papillary Thyroid Cancer (conventional type) involving the skeletal muscle and one out of six right cervical neck lymph nodes. The resection margins were negative for carcinoma. Post operatively the patient received radioactive iodine treatment and Levothyroxine was initiated. DISCUSSION:In Endocrine practice, the use of thyroid ultrasonography is common. However, the clinician is usually prompted to order an ultrasound due to consistent abnormal thyroid studies revealing thyrotoxicosis and/or abnormal physical exam findings such as nodular goiter. Or in the case of known diagnoses such as thyroid cancer, it is useful for pre and post surgical management. Nonetheless, in some cases, when ordered outside of common practice, unexpected pathology may be discovered. CONCLUSION:This case demonstrated an unexpected finding of metastatic papillary thyroid cancer , despite initial presentation of abnormal thyroid function tests with normal repeat result and physical exam. Thyroid ultrasound was useful in revealing the diagnosis, preventing a delay in treatment. Presentation Date: Saturday, June 17, 2023