MON-341 The Case of the Phantom Thyroid: Residual Hemostatic Material Mimicking Cancer Recurrence

Abstract Disclosure: P. Arumugam: None. M. Arumugam: None. A 29-year-old female was diagnosed with papillary thyroid cancer following a fine-needle aspiration of a left-sided thyroid nodule. The patient underwent total thyroidectomy in another country. Pathology revealed a 2 cm focus of PTC with negative margins and no lymph node involvement. Post-surgery, thyroglobulin (TG) was measured at 0.1 ng/mL, and anti-thyroglobulin antibodies were 83 IU/mL. Patient did not receive radioactive iodine therapy. The patient presented to our clinic 3 months post-thyroidectomy for follow-up. A thyroid ultrasound showed a heterogeneous thyroid without evidence of hypervascularity. A CT soft tissue neck scan revealed material within the thyroid bed and along the anterior midline at the level of the sternoclavicular joints. Three months post op thyroglobulin level was 0.2 ng/mL, and anti-TG antibodies had decreased to 2 IU/mL. A biopsy of the thyroid bed was performed, which revealed no thyroid tissue or malignant cells. Instead, foreign material and giant cells were identified. Conclusion: Given the stable thyroglobulin levels and the significant reduction in anti-TG antibodies, along with biopsy results indicating foreign material, it is concluded that the "thyroid tissue" observed on the ultrasound is likely residual hemostatic material left over from surgery. This material has occupied the thyroid bed and is masquerading as thyroid tissue. The findings suggest a post-surgical complication rather than recurrence of thyroid cancer or malignancy. The patient’s clinical course should continue to be monitored, with consideration for any further management or intervention if necessary. Presentation: Monday, July 14, 2025