MULTIFOCALITY AND BILATERALITY IN MEDULLARY THYROID CANCER: BASIS FOR A PROOF-OF-CONCEPT SAFETY OF LOBECTOMY

Objective: At the present, total thyroidectomy and central neck dissection is the surgical approach recommended for the initial treatment of medullary thyroid cancer (MTC) independently from the size, number of tumor foci, age of patients and other demographics and clinical-pathological parameters. The aims of the present study were to assess the prevalence of multifocality in hereditary (hMTC) and sporadic (sMTC) patients and to correlate the presence of multifocality with clinical and pathological parameters to provide a proof of concept that lobectomy can be safely performed in selected cases. Methods: We analyzed the epidemiological, pathological and clinical data of 389 MTC (311 sMTC and 78 hMTC) diagnosed in our center from 2005 to 2018. Results: Multifocality was found in 89/389 cases (22.9%), [45/311 (14.5%) sMTC and 44/78 (56.4%) hMTC]. The bilaterality has been detected in 27/311 (8.7%) of all sMTC, particularly in 27/45 (60%) of multifocal ones, and in 44/78 of hMTC (56.4%). Multifocality resulted correlated to a more aggressive phenotype in both sMTC and hMTC and the multivariate analysis showed that was statistically and independently associated with the tumoral extrathyroidal extension and N1 status in sMTC and with N1 status and persistent disease in hMTC. However, none of the presurgical factors could predict the presence of both multifocality and bilaterality. Conclusions: our study demonstrated that the rarity of multifocality and in particular of bilaterality in sMTC represents the proof of concept for starting to think to a more conservative surgical approach in selected sMTC cases. This approach cannot be considered in hMTC for the high prevalence of multifocal and bilateral cases.