Endocrine Abstracts

Follicular variant papillary thyroid cancer (FV-PTC) appeared to be the most common subtype representing between 9 and 22.5% of all PTC cases. With the dramatic increase in thyroid cancer incidence, FV-PTC has also been increasingly diagnosed in recent times. Despite its high incidence, the clinical behaviour, prognosis and outcome of FV-PTC remains controversial and challenging for most physicians. This study aims to compare the disease characteristics of FV-PTC with Classic-PTC and FTC in a single institution in the Philippines. This is a retrospective cohort study of 606 thyroid cancer patients diagnosed as C-PTC (n=440), FV-PTC (n=87) or FTC (n=79) by biopsy. Different clinical variables of three groups were then compared using a univariate logistic regression analysis. FV-PTC and C-PTC presented similarly with higher rates of multifocality (25.3% and 22.7% vs 7.6%) and bilateral involvement (20.7% and 17.1% vs 6.3%) as compared to FTC. C-PTC (37.7%) presented with high nodal involvement at presentation while both FV-PTC (8.1%) and FTC (7.6%) presented with less nodal metastases. Distant metastases was observed highest among the FTC (12.7%) group followed by FV-PTC (5.8%) and rarely in C-PTC (3.4%). Majority of patients underwent complete thyroidectomy and post-surgical radioactive iodine ablative therapy with similar rates across the groups. Recurrence rate was observed to be highest among C-PTC (39.4%) while FV-PTC (18.4%) had the lowest recurrence rate. FV-PTC resulted in almost 50% reduction (HR=0.4934; P value=0.007) in recurrence risk as compared with C-PTC. Mortality rate was highest among FTC (2.5%) group while FV-PTC (0%) and C-PTC (0.5%) had a similarly low mortality rate. FV-PTC represents a major sub-type of PTC that represents an intermediate entity between C-PTC and FTC. Although it behaves clinically like FTC presenting with lower lymph node metastases and higher distant metastases than C-PTC, its long-term survival and prognosis is quite similar with that of C-PTC. Treatment recommendations for C-PTC and FTC can be applied to FV-PTC cases.