Endocrine Abstracts

Papillary thyroid cancer (PTC) is the most frequent thyroid tumour. Medullary thyroid cancer (MTC) however, is very rare. We report a case of coexistent medullary and papillary carcinomas in two different foci in a patient with family history of TPC in a first-degree relative.

Case: A 65-year-old female was examined for multinodular goiter (MNG). She had a family history of thyroid papillary carcinoma in her elder sister. Free T₄, free T₃, and TSH levels were within normal limits. Neck ultrasound (US) displayed solid, hypo-echoic nodules >3 cm at the both lobes of the thyroid gland. The results of fine-needle aspiration cytology (FNAC) of the both nodules were benign. Patient preferred surgery because of the nodule size and positive family history. Histopathology results revealed MTC which is 4 mm in diameter in the right lobe and PTC follicular variant 12 mm in diameter in the left lobe. Postoperative calcitonin was 56 pg/ml and CEA was in normal limits. Completion thyroidectomy and lymph node dissection also performed. No residue was detected by post-operative neck US. Neck and chest CT and liver MRI which were performed for MTC metastasis were all negatives. RET protooncogen mutation was negative unless BRAF^V600E mutation was positive. Patient’s younger sister was also examined for MNG. Thyroid US displayed solid, hypoechoic nodules >2 cm in both lobes. FNAC of nodules were reported as suspicious for PTC. Patient underwent total thyroidectomy and central lymph node dissection and diagnosed as PTC on both lobes.

Discussion: FNAC is the most accurate method for evaluating thyroid nodules. False negative rate of FNAC is about 5%, so malignancy risk of benign results should be kept in mind especially with a positive family history of thyroid carcinoma in a first-degree relative. We presented a coincidental coexistence of MTC and PTC case to point to this risk.