Cytomorphological analysis of histologically confirmed cases of medullary thyroid carcinoma

Abstract Medullary thyroid carcinoma (MTC) is a rare neuroendocrine malignant tumor of parafollicular C-cell origin of the thyroid gland, whose tumor cells typically produce calcitonin. The serum level of calcitonin produced by tumor cells is a sensitive tumor marker. An elevated serum level of this and the simultaneous presence of a thyroid nodule confirmed by ultrasound raise a reasonable suspicion of MTC. Still, the first-line MTC confirmation method in diagnosing MTC is fine-needle aspiration cytology (FNA). Objective: The aim of our study was the clinicopathological and cytomorphological analysis of histologically confirmed MTC cases obtained with FNA, as well as their comparison with the clinicopathological and cytomorphological characteristics of papillary thyroid carcinoma (PTC). Material and method: In our retrospective study, we analyzed the FNA cytology findings of patients with nodular goiter examined between 2013-2019 and the available clinical data. Results: In the 7-year period, 1,808 fine-needle aspiration examinations were performed, of which we identified 12 MTC and 77 PTC cases. The average age of patients diagnosed with MTC was 53±13 years. There were nine women and three men in examined cases. The average diameter of the nodules was 14±5 mm. All of our cases were of the sporadic type. The average age of patients diagnosed with MTC was greater than that of patients diagnosed with PTC (53 vs. 44 years, p=0.02367). A female predominance is observed in both diseases, although this is more pronounced in PTC. The diameter of the MTC nodules does not differ significantly from the mean size of the PTC nodules (14 vs. 17 mm, p=0.3138). The cytomorphological characteristics of the MTC cases we examined correspond to those described in the international literature, with minor differences. Conclusions: MTC is one of the rarer thyroid cancers, which is often difficult to distinguish from other types of thyroid cancer based on clinical features alone. Average age at diagnosis is greater than patients with PTC. Accurate diagnosis is critical as it requires a different approach than other types of thyroid cancer, it may require a different surgical approach, and may benefit from targeted therapy. Therefore, knowledge of the cytomorphology of MTC is essential for accurate diagnosis and optimal patient care.