Endocrine Abstracts

Aim: Papillary thyroid cancer (PTC) accounts for 85% of thyroid cancers. Classical PTC has a 10 year survival rate of over 95%. Although the histopathological diagnosis of thyroid tumors, which started in the 1950s, has improved significantly in the last few decades, the effect of aggressive subtypes on survival has not been fully clarified. In our study, we investigated the effect of aggressive cytologic subtypes on behavior and prognosis in patients followed up with a diagnosis of PTC.

Method: Our retrospective study included 484 patients who underwent bilateral total thyroidectomy and were diagnosed with PTC. There were 11 patients with aggressive subtype (columnar cell, tall cell, diffuse sclerosing, solid, hobnail PTC), 382 patients with nonaggressive subtype (papillary, follicular PTC), and 91 patients with mixed subtype. 36 month follow-up results were analyzed. Demographicall findings, imaging and laboratory results, histopathological features (tumor diameter, capsule invasion, vascular invasion, extrathyroidal invasion, lymphatic invasion, distant metastasis), radioactive iodine (RAI) treatment were noted from the records. Dynamic risk scoring (excellent response, biochemical incomplete response, structural incomplete response, indeterminate response) was performed.

Results: The mean age at diagnosis was lower in the aggressive subtypes (44.36±10.63) than in the nonaggressive and mixed subtypes (46.14±12.82 and 47.71±13.24, respectively) (P=0.501). Tumor size was significantly larger in the aggressive subtypes (1.83±2.27 cm) than in the nonaggressive and mixed subtypes (1.21±1.1 cm and 1.60±1.1 cm, respectively) (P=0.019). According to the American Thyroid Association (ATA) risk classification, the proportions of those identified as intermediate and high risk were higher in the aggressive and mixed subtypes (72.7% and 68.1%, respectively) than in the nonaggressive subtypes (23.9%) and the difference was statistically significant (P<0.001). Remission, persistence, recurrence and metastasis rates during follow-up did not differ significantly between groups (P=0.926, P=0.903, P=0.776 and P=0.920, respectively). There was no significant difference in treatment responses according to dynamic risk scoring after initial treatment 6-12 months, 12-18 months, 18-24 months, 24-36 months (P=0.931, P=0.961, P=0.892, P=0.698, respectively).

Conclusion: In our study, we found that tumor size was larger in the aggressive subtype, and those with intermediate and high risk, according to the ATA risk classification, were more common in the aggressive and mixed subtypes. In patients with PTC, aggressive and mixed subtypes in the initial treatment phase may create differences in approach, and further studies are needed.