Endocrine Abstracts

Introduction: Papillary thyroid carcinoma(PTC) and medullary thyroid carcinoma(MTC) have always been considered different tumors. Concomitant presence of MTC and PTC in the same patient is a rare clinical event.

Case report: A 43 year-old woman admitted with fatigue, a serum thyrotropin of 4.6 uIU/ml and a 15×11 mm thyroid nodule in right lobe detected in another center. Fine needle aspiration(FNA) of the nodule was consistent with MTC. In family history, her mother had thyroid cancer but the type was unknown. Repeat thyroid ultrasonography revealed a 14×11.8×18.4 mm solitary thyroid nodule in right lobe. There were also suspicious lymph nodes in right level VI and IV and left level IV. FNA along with tyroglobuline and calcitonin wash-out was performed to lymph nodes and thyroglobulin levels were 8423, 373.3 and 0.3 ng/ml respectively while calcitonin wash-out results were >2000 pg/ml in all lymph nodes. FNA cytologies were atypia of undetermined significance for the right and nondiagnostic for the left lymph nodes. Serum calcitonin was 655 pg/ml (<5 pg/ml) and carcinoembryonic antigen(CEA) was 45.1 ng/ml (0–3.4 ng/ml). Evaluation for concomitant primary hyperparathyroidism and pheochromocytoma revealed no pathology. Total thyroidectomy with right lateral, left lateral and bilateral central lymph node dissection was performed. Pathology of the nodule was reported as 17×14 mm mixed medullary and papillary thyroid carcinoma’. Immunhistochemistry was positive for TTF-1 and calcitonin, and in focal areas thyroglobuline, CK-19 and HMBE-1 stainings were positive. One right lateral and three right central lymph node were tumour positive. The patient received 150 mCi radioactive iodine ablation therapy. Stimulated thyroglobuline was 4.2 ng/ml and a focal activity uptake in thyroid location was seen in postablative whole body scanning. Serum calcitonin and CEA regressed to 20.0 pg/ml and 2.7 ng/ml, respectively. The patient was heterozygote for C2410G>A (VAL804MET) mutation in RET protooncogene analysis. 26-year old daughter of the patient was also heterozygote for C2410G>A (VAL804MET) while other daughter had no mutation. Mutation carrier daughter of patient preferred active surveillance rather than prophylactic thyroidectomy.

Conclusion: Our patient is one of the rare cases of mixed medullary and papillary thyroid carcinoma that was evaluated completely both clinically and genetically. Mixed medullary and papillary thyroid carcinoma is a rare clinical entity but merits consideration in differential diagnosis of thyroid nodules particularly in patients with a family history of thyroid malignancy.