Endocrine Abstracts

Introduction: the presence of areas with a solid / trabecular growth pattern in differentiated papillary thyroid carcinoma (PTC) represents a source of controversy regarding clinical and prognostic significance and usually requires a more aggressive therapeutic approach. The aim of this study was to compare clinicopathological characteristics, treatments and prognosis of PTC with and without solid component (SC). We also aimed to evaluate whether SC affects patient outcome in the absence of aggressive features.

Material and methods: We studied 300 patients with PTC with follow-up for more than 5 years. All PTC with any percentage of SC were included. Poorly differentiated thyroid carcinoma was excluded from this analysis. Study data were analyzed using the Chi-square and Student’s T-test. Global survival (GS) and disease-specific survival (DSS) were analyzed using Kaplan-Meier survival curves.

Results: There were 300 cases of PTC, 99 (33.0%) with SC and 201 (67.0%) without SC (mean follow-up time 9.5 years). Mean tumor size was larger in the presence of SC (35.2 ± 17.5 vs 25.3 ± 16.2 mm, respectively for PTC with SC and PTC without SC, P < 0.001). A SC was not associated with a higher prevalence of extrathyroidal extension (27.3% vs 28.9%, P = 0.775) or locorregional invasion (4.1% vs 4.5%, P= 0.100). Vascular invasion was more frequent in PTC with SC (43.4% vs 18.9%, P < 0.001). The prevalence of lymph node metastases was similar between the two groups (24.2% vs 24.9%, P = 0.905), but distant metastases were more frequent in the group of PTC with SC (19.2% vs 8.5%, P = 0.007). Total activity of radioactive iodine (RAI) was significantly higher in PTC with SC (P = 0.001). Disease recurrence rates were similar between both groups (12.1% vs 10.9%, P = 0.763). At last follow-up, GS and DSS were similar in patients with and without SC (93.9% % vs 98.0%, P = 0.084; 99.0% vs 99.5%, P = 0.549, respectively). A subanalysis excluding the cases with vascular invasion showed no differences in the percentage of distant metastases, OS and DSS between the groups. However, RAI was significantly higher in the group with SC (P = 0.026).

Conclusion: Clinicopathologic features were similar between PTC with and without SC. There was a higher prevalence of vascular invasion in PTC with SC which might explain the higher incidence of distant metastasis in this group. However, the presence of SC was not related to less favorable prognosis or lower survival rates. In the absence of features of aggressiveness, the clinical impact of the SC alone is negligible.