Thyroid micro-carcinoma: only a diagnostic epidemic?

BACKGROUND: The incidence of thyroid carcinoma ranges from 0.5 to 10 cases every 100,000, depending on the country, the context and purpose of the study. The high incidence of differentiated thyroid tumor is continuously growing. While most malignant pathologies affect the adults, a proportion of 1-2% of pediatric population is affected by solitary nodule, of which some are malignant cancers. Studying thyroid malignant cancer, the most sensitive and accurate imaging technique is color Doppler ultrasonography. Fine needle aspiration cytology (FNAC), if correctly performed, is the key to a correct diagnosis.

METHODS: This prospective study analyzes 1726 cases of total thyroidectomy and lobectomy performed between January 2004 and December 2013. The cytology sampling has been done following standard FNAC or capillary aspiration. Results have been classified in five classes, following the Italian SIAPEC-AIT system (2008). Sensibility, specificity, accuracy, negative predictive value and positive for the evaluation of FNAC technique are the statistical parameters considered.

RESULTS: The outcome is aligned with what already known in literature, that FNAC has sensibility between 60-98% and specificity between 72-100%. Considering Tir3 as a low malignancy risk category therefore not suitable for surgery, those values decrease.

CONCLUSIONS: Micro-carcinoma is a more represented entity than apparently suspected. Nowadays, cytology is the most precise diagnostic support to the therapeutic management of thyroid node, yet it is still charged with false negatives. The evaluation of data records, combined with some molecular biology techniques and applied to cytology, could help in giving more appropriate surgical indication, allowing the surgery to be therapeutic more than diagnostic.