Endocrine Abstracts

Introduction: Follicular variant papillary thyroid carcinoma (FVPTC) is the most common variant of papillary thyroid carcinoma (PTC) after classical PTC (CPTC). In this study, we aimed to compare functional status, ultrasonographical features, cytological results and histopathological characteristics of patients with CPTC and FVPTC.

Methods: Patients diagnosed with CPTC and FVPTC in our clinic were reviewed retrospectively. Data of preoperative thyroid functional status, thyroid autoantibodies and ultrasonographical features were obtained from the records. Sensitivity of fine needle aspiration biopsy (FNAB) was calculated and histopathological features were compared in two variants.

Results: There were 322 (80.1%) CPTC and 80 (19.9%) FVPTC patients and sex distribution, mean age, thyroid functions and autoantibody positivity rates were similar. 228 CPTC and 62 FVPTC patients had preoperative US examination. Echogenicity, texture, presence of microcalcifications and macrocalcifications were similar in two groups. A hypoechoic halo was observed more frequently (15.4 vs 29%, P=0.012) and marginal irregularity was observed less commonly (81.6 vs 67.7%, P=0.018) in FVPTC lesions. Among 261 CPTC and 73 FVPTC patients with preoperative FNAB results, rate of malignant cytology was significantly higher in CPTC (37.2 vs 19.2%, P=0.004) and rate of suspicious cytology was significantly higher in FVPTC (35.6 vs 53.4%, P=0.006). When only malignant cytology was treated as true positive, sensitivity of FNAB in CPTC and FVPTC was 37.2 and 19.2%, respectively (P=0.004). Mean tumor diameter was markedly higher in FVPTC compared to CPTC (16.04±13.44 vs 10.88±9.88 mm, P<0.001). There was no difference in terms of multicentricity, capsule and vascular invasion, extrathyroidal involvement and lymph node invasion.

Conclusion: FVPTC tends to have more benign features in US and less malignant results in cytology. Higher tumor size in FVPTC compared to CPTC might be explained by the recognition of clinical importance of these lesions after reaching particular sizes due to benign US features.