Endocrine Abstracts (2017) 49 EP1475 | DOI: 10.1530/endoabs.49.EP1475

Minimally and widely invasive follicular thyroid carcinomas: are there significant differences in clinical behaviour and prognosis?

Diana Martins1, Cristina Ribeiro1, Miguel Melo1, Joana Saraiva1, Maria João Martins2, Carla Baptista1, Diana Oliveira1, Mara Ventura1, Adriana Lages1, Nelson Cunha1, Diana Catarino1, Lúcia Fadiga1, Gracinda Costa3 & Francisco Carrilho1

1Endocrinology, Diabetes and Metabolism Department of Coimbra Hospital and University Centre, Coimbra, Portugal; 2Anatomic Pathology Department of Coimbra Hospital and Universitary Centre, Coimbra, Portugal; 3Nuclear Medicine Department of Endocrinology, Diabetes and Metabolism Department of Coimbra Hospital and Universitary Centre, Coimbra, Portugal.

Introduction: The existence of clear differences between the biological course and clinical behaviour of minimally invasive (MI) and widely invasive (WI) follicular thyroid carcinomas (FTC) is still debatable. The present study was conducted to outline the clinical differences between MI and WI-FTC and evaluate outcomes in both tumors.

Methods: We conducted a retrospective cohort study involving 80 cases of FTC. The comparison between MI-FTC and WI-FTC included an evaluation of clinic-pathologic characteristics, including tumor staging, and outcome assessment.

Results: The cohort included 65 patients with MI-FTC and 15 patients with WI-FTC. Patients whose age at diagnosis was ≥45 years more frequently had WI-FTC (27.3% Vs 4.0%, P=0.023). Mean tumor size was significantly greater in WI-FTC patients than in the MI-FTC (43.07 vs 30.94 mm, P=0.007). At univariate analysis, vascular invasion, infiltrative margins and invasion of thyroid capsule were significantly related to the presence of WI-FTC (P<0.001, P<0.001 and P=0.010, respectively). A higher cancer stage (III–IV) was also associated with the occurrence of WI-FTC (50% vs 8.6%, P<0.001). After a mean follow-up of 52.6 and 76.4 months in MI and WI-FTC, respectively, one patient of the first group and two patients of the second died of FTC. Patients with MI and WI tumors respectively presented a disease-free survival of 100% and 84% at 10 years.

Conclusions: The study reported a good outcome in both MI and WI patients, probably related to an aggressive therapeutic strategy and strict follow-up. Our data confirm previous studies which showed that WI-FTC are typically larger tumors with higher stage, more frequent vascular invasion and invasion of the thyroid capsule. Accordingly, we believe that the tumor grade of invasiveness must be taken into account on the staging process of disease.