SAT-297 Papillary Carcinoma Tall Cell Subtype Variant with Paraneoplastic Syndrome

Abstract Disclosure: J. Gill: None. D. Escalante: None. A 51-year-old female with a history of papillary thyroid carcinoma (PTC) presented with a complex clinical course involving multiple systemic manifestations and imaging findings suggestive of metastatic disease. Initial symptoms included right neck tenderness, hoarseness, dysphagia, dyspnea, excessive fatigue, nervousness, heat intolerance, and dry skin, along with a family history of malignancies, suggesting a possible genetic predisposition. Diagnostic imaging revealed multiple thyroid nodules, including a 26 mm nodule in the right thyroid lobe with coarse calcifications, and enlarged cervical lymph nodes with calcifications, raising suspicion for thyroid malignancy with regional nodal metastasis. Fine needle aspiration (FNA) confirmed the diagnosis of PTC with a tall cell variant, and staging indicated mT2, pN1b (2-4 cm), with bilateral cervical lymph node involvement. The patient underwent total thyroidectomy and bilateral central lymph node dissection, with parathyroid hormone auto-transplantation due to intraoperative damage.Postoperatively, she developed hypothyroidism and hypoparathyroidism, for which she was started on levothyroxine, liothyronine, and calcitriol. One month following surgery, her thyroglobulin (Tg) level was 375.2 ng/mL, and a whole-body iodine-131 (RAI) scan revealed diffuse pulmonary uptake, suggestive of pulmonary metastases, confirmed by follow-up CT imaging. The patient was treated with 197 mCi of RAI, but no new changes were noted on subsequent scans.Eight months postoperatively, the patient developed neurological symptoms, including headache, diplopia, ataxia, and paresthesia. Meningitis was initially suspected, but extensive investigations including brain imaging, lumbar puncture, and orbital MRI were negative. She was eventually diagnosed with paraneoplastic syndrome and responded to high-dose methylprednisolone, with complete resolution of symptoms.Two years post-thyroidectomy, a CT scan identified a spiculated mass in the right abdominal wall, diagnosed as a desmoid tumor (fibroblastic/myofibroblastic fibromatosis), which was surgically excised. Post-surgical evaluation showed negative Thyroglobulin and Thyroglobulin antibodies, and stable thyroid function on hormone replacement therapy. However, a subsequent rise in Thyroglobulin to 1 ng/mL with elevated TSH and low FT4 levels raised concern for possible recurrence, despite negative imaging for metastatic disease.This case underscores the challenges in managing advanced PTC with complex clinical presentations, including paraneoplastic syndromes and atypical tumor-related manifestations. The persistent elevation of Thyroglobulin despite stable imaging findings necessitates ongoing surveillance to detect early recurrence or metastasis. Presentation: Saturday, July 12, 2025