Is unicentric familial papillary thyroid microcarcinoma different from multicentric?

Background Familial papillary thyroid microcarcinoma (FPTMC) appears to be more aggressive than sporadic papillary thyroid microcarcinoma (SPTMC). However, there are authors who indicate that unicentric FPTMC has a similar prognosis to SPTMC. The objective is to analyze whether unicentric FPTMC has a better prognosis than multicentric FPTMC. Design and methods Type of study: National multicenter longitudinal analytical observational study. Study population: Patients with FPTMC. Study groups: Two groups were compared: Group A (unicentric FPTMC) vs. Group B (multicentric FPTMC). Study variables: It is analyzed whether between the groups there are: a) differentiating characteristics; and b) prognostic differences. Statistical analysis: Cox regression analysis and survival analysis. Results Ninety-four patients were included, 44% (n = 41) with unicentric FPTMC and 56% (n = 53) with multicentric FPTMC. No differences were observed between the groups according to socio-familial, clinical or histological variables. In the group B a more aggressive treatment was performed, with higher frequency of total thyroidectomy (99 vs. 78%; p = 0.003), lymph node dissection (41 vs. 15%; p = 0.005) and therapy with radioactive iodine (96 vs. 73%; p = 0.002). Tumor stage was similar in both groups (p = 0.237), with a higher number of T3 cases in the group B (24 vs. 5%; p = 0.009). After a mean follow-up of 90 +/- 68.95 months, the oncological results were similar, with a similar disease persistence rate (9 vs. 5%; p = 0.337), disease recurrence rate (21 vs. 8%; p = 0.159) and disease-free survival (p = 0.075). Conclusions Unicentric FPTMC should not be considered as a SPTMC due to its prognosis is similar to multicentric FPTMC.