Clinicopathological significance of a solid component in papillary thyroid carcinoma

Solid variant of papillary thyroid carcinoma (SVPTC) is characterized by a solid component (SC) involving more than 50% of the tumour with the preservation of the classical cytological features of papillary thyroid carcinoma (PTC). However, the clinical significance of SC in PTC has been rarely examined. Herein, we investigated retrospectively the clinicopathological features of PTC with various degrees (10-85%) of SC (PTCSC).

Patients with PTCSC (n = 27) were stratified into SC-major (SC > 50% of the tumour) and SC-minor (SC < 49%) groups. The clinicopathological parameters were compared to the well-differentiated PTC (WPTC) group (n = 47). Both SC-minor (n = 18) and SC-major (n = 9) groups had increased incidence of a large-sized tumour, extracapsular extension and a high recurrence rate, compared to WPTC. Disease-free survival (DFS) of both SC-minor and SC-major was shorter than that of WPTC (P = 0.035 and P = 0.016, respectively). Overall survival was similar among all the groups. Univariate analysis revealed that SC was associated significantly with a recurrence rate (P = 0.018). Using multivariate analysis, SC appeared to be associated with a recurrence rate with borderline significance (P = 0.055).

Our findings indicate that the presence of SC in PTC, regardless of the proportion, is associated with adverse clinical parameters and a shorter DFS.