Abstract
OBJECTIVE: Familial non-medullary thyroid cancer (FNMTC) is defined as non-medullary thyroid cancer occurring in two or more first-degree relatives, without features of known hereditary syndromes. Although familial predisposition is well established, its clinical behavior remains debated. This study aimed at characterizing familial cases compared to sporadic non-medullary thyroid cancer (SNMTC). SUBJECTS AND METHODS: FNMTC and SNMTC patients were recruited from the Endocrine Division (SEMPR) of the Federal University of Paraná, Brazil, and private endocrine clinics in Curitiba, Paraná, Brazil (2000-2019). Baseline, histopathological, and clinical data were analyzed using SPSS Statistics 26.0. Statistical comparisons employed chi-square, Student's t test, and Mann-Whitney U test, as appropriate. Post hoc power analysis was performed using G*Power 3.1.9.7, and R 2025.05.0. RESULTS: We analyzed 39 FNMTC and 119 SNMTC patients. Papillary thyroid carcinoma was the predominant histological type in both groups. FNMTC patients were diagnosed at a younger age (38.5 ± 14.2 vs. 46.6 ± 13.8 years, p = 0.003) and more frequently presented with lymph node metastases at diagnosis (46.2% vs. 21.8%, p = 0.007), with a 4.57-fold increased risk. Despite these differences, long-term outcomes did not differ significantly between groups. An earlier disease onset in subsequent generation suggests a possible anticipation phenomenon. CONCLUSION: These findings suggest that FNMTC patients may present with earlier onset and higher rates of lymph node involvement, underscoring the need for thorough preoperative lateral neck evaluation. In view of a possible anticipation phenomenon, cervical ultrasound screening might be considered starting in adolescence.