Patients with Indeterminate Thyroid Nodules at Cytology and Cancer at Histology Have a More Favorable Outcome Compared with Patients with Suspicious or Malignant Cytology

Abstract

Background: The outcomes of patients with thyroid cancer proven by histology in patients in whom cytology was Thy 3 (indeterminate; Thy 3 patients in this study) based on the Italian consensus classification compared with those in whom cytology was Thy 4 (suspicious for malignancy) or Thy 5 (indicative for malignancy) (Thy 4-5 patients here) remains unclear.

Objective: To analyze the outcome of 371 Thy 3 patients versus 269 Thy 4-5 patients homogeneously treated with total thyroidectomy and ¹³¹I activity.

Results: T1 stage was observed in 46.0% of Thy 3 and in 38.8% of Thy 4-5 patients (p = 0.02), N0 in 95.9% of Thy 3 and in 75.5% of Thy 4-5 patients (p < 0.0001). 35/261 (9.6%) Thy 3 and 85/269 (31.5%) Thy 4-5 patients required >30 mCi of ¹³¹I (p < 0.0001). 359/371 (96.8%) Thy 3 and 232/269 (86.2%) Thy 4-5 patients were free of disease at the end of follow-up (p < 0.001). The time required to obtain 50% of patients in remission was 2 years in Thy 3 and 4 years in Thy 4-5 patients (p < 0.001). The most common histological type was the follicular variant of papillary thyroid carcinoma (FV-PTC) in Thy 3 patients (239/371, 64.4%) and the classic variant in Thy 4-5 patients (185/269; 68.8%). The FV-PTC had better prognostic features compared with the other PTC variants: T1 stage was observed in 133/277 (48.0%) FV-PTC patients and in 146/363 (40.0%) patients with the other variants (p < 0.001), N0 was present in 265/277 (96.0%) FV-PTC and in 290/363 (79.8%) patients with the other variants (p < 0.001). Overall, 267/277 FV-PTC patients (96.4%) and 324/363 patients (89.0%) with the other variants were free of disease (p < 0.0008) at the end of follow-up, and the time required to obtain 50% of patients in remission was 2 years in FV-PTC and 4.0 years in the other variants (p < 0.001).

Conclusion: Patients with Thy 3 cytology have better outcomes of thyroid cancer compared with patients with Thy 4 or Thy 5 cytology, and indeterminate cytology is commonly associated with the less aggressive FV-PTC.

Keywords: indeterminate cytology; thyroid; thyroid cancer; thyroid nodules.