(18)F-DOPA PET/CT seems to be the most useful imaging method for detecting recurrent MTC lesions in patients with elevated serum calcitonin levels, performing better than (18)F-FDG and (68)Ga-somatostatin analogue PET/CT. (18)F-FDG may complement (18)F-DOPA in patients with an aggressive tumour.

Objective: Multiple endocrine neoplasia type 2 (MEN 2) is a genetic disease characterized by medullary thyroid carcinoma (MTC) associated (MEN 2A and 2B) or not familial MTC (FMTC) with other endocrine neoplasia due to germline RET gene mutations. The prevalence of these rare genetic diseases and their corresponding RET mutations are unknown due to the small size of the study population. Methods: We collected data on germline RET mutations of 250 families with hereditary MTC followed in 20 different Italian centres. Results and conclusions: The most frequent RET amino acid substitution was Val804Met (19.6%) followed by Cys634Arg (13.6%). A total of 40 different germline RET mutations were present. Six families (2.4%) were negative for germline RET mutations. The comparison of the prevalence of RET germline mutations in the present study with those published by other European studies showed a higher prevalence of Val804Met and Ser891Ala mutations and a lower prevalence of Leu790Phe and Tyr791Phe (P!0.0001). A statistically significant higher prevalence of mutations affecting non-cysteine codons was also found (P!0.0001). Furthermore, the phenotype data collection showed an unexpected higher prevalence of FMTC (57.6%) with respect to other MEN 2 syndromes (34% MEN 2A and 6.8% of MEN 2B). In conclusion, we observed a statistically significant different pattern of RET mutations in Italian MEN 2 families with respect to other European studies and a higher prevalence of FMTC phenotype. The different ethnic origins of the patients and the particular attention given to analysing apparently sporadic MTC for RET germline mutations may explain these findings.

This study shows, as the first in a multicentre series, that FNA-CT sensitivity is higher than that of cytology in diagnosing MTC. To avoid false-negative MTC by cytology, CT measurement in aspiration needle washout is to be performed in all patients undergoing biopsy following high serum CT.