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[Clinicopathological features and molecular characteristics of tall cell and hobnail variants of papillary thyroid carcinoma].

Objective: To investigate the clinicopathological and molecular genetic characteristics of tall cell variant and hobnail variant of papillary thyroid carcinoma (PTC). Methods: Twenty-one cases of tall cell variant (TCV-PTC) of PTC (TCV-PTC) and ten cases of hobnail variant of PTC (HV-PTC), as the highly aggressive group, were collected from Xuanwu Hospital from August 2009 to August 2015. Twenty-two cases of follicular variant and 21 classical PTC cases were included as control. Relevant clinical and pathologic data were obtained, and in some cases, paraffin samples were selected for gene mutation spectrum analysis using second generation sequencing. Results: There were 18 males and 56 females; 57 patients were younger than 55 years of age, and 17 patients were 55 years or older. The mean tumor size was 1.6 cm for the high-aggressive group (TCV-PTC and HV-PTC), 1.1 cm for the follicular subtype, and 1.6 cm for the classical type. There were 54 cases with thyroid capsule invasion, 24 cases with extra-thyroidal invasion, and 45 patients with lymph node metastases. Regional recurrence occurred in 7 cases, no recurrence in 54 cases, and 13 patients were lost to follow-up. The highly aggressive group was more likely to show extra-thyroidal invasion, lymph node metastases and recurrence than those with classical PTC (P<0.05). Within this cohort, BRAF V600E mutation was detected in 53 cases and TERT promoter mutation in 6 cases. Compared with the single mutation group and no mutation group, BRAF and TERT promoter co-mutation group was more commonly detected in older age, male, larger tumor size and more prone to extra-thyroid invasion (P<0.05). In addition, among BRAF and TERT co-mutation cases, the highly-aggressive group accounted for the highest proportion (5/6). Conclusions: TCV-PTC and HV-PTC, as highly-aggressive variants of PTC, show more aggressive biologic behavior (more lymph node metastasis, external thyroid invasion and recurrences) than the classical and follicular variants of PTC. Coexisting BRAF and TERT promoter mutations may be associated with invasive biologic behavior.