The Difficulty of Post-Operative Surveillance of Calcitonin Negative Medullary Thyroid Cancer

• Published in: Journal of the Endocrine Society 2021-05, Vol.5 (Supplement_1), p.A901-A901
• Main Authors: Skutnik, Emily, Kinney, Rachel, Lopes, Rebecca, Siu, Chun, Magdaleno, Angela, Perilli, Gretchen
• Format: Article
• Language: English
• Subjects: Thyroid
• ISSN: 2472-1972; 2472-1972
• DOI: 10.1210/jendso/bvab048.1839

Background: As a differentiated thyroid tumor, medullary thyroid cancer (MTC) typically maintains the secretory function of the c-cells with resultant increase in serum calcitonin level along with frequent elevations in serum chromogranin A (CgA) and carcinoembryonic antigen (CEA). Clinical Presentation: A 71-year-old female with history of multinodular goiter underwent a thyroid nodule biopsy after routine ultrasound surveillance revealed enlargement of two right lower lobe nodules compared with prior imaging. Fine needle aspiration (FNA) of one 3.1 x 1.9 x 2.7 cm right thyroid nodule revealed cellular material composed of spindle-shaped neoplastic cells, some of them with marked cytologic atypia, suspicious for a neuroendocrine tumor, specifically medullary thyroid carcinoma. A PET/CT scan was performed after injection of Gallium-68 dotatate radiotracer and revealed intense focal radiotracer activity in the approximately 2.5 x 2.1 cm right thyroid mid lower pole heterogeneous hypodense mass with tiny calcification inferiorly, consistent with the patient’s known tumor. There was no evidence of cervical octreotate avid metastatic lymphadenopathy and a chest x-ray showed no evidence of active pulmonary disease. The patient subsequently underwent a right partial thyroidectomy with isthmusectomy. Histopathology revealed a 2.8 x 1.9 x 1.9 cm neoplasm composed of spindle and polygonal cells growing in solid nests with neuroendocrine-type nuclei. Immunostains showed the tumor to be positive for AE1-AE3 cytokeratins, chromogranin, synaptophysin and CEA. It was focally positive for TTF-1 and calcitonin. Thyroglobulin and PAX-8 were negative. Using the AJCC 8th edition staging system, the tumor was staged a pT2Nx with margins uninvolved by carcinoma and no extrathyroidal extension or lymphatic invasion. Angioinvasion was present. Additional serum studies included a normal calcitonin value of