Abstract
Purpose
Recent diagnostic criteria updates of the tall cell variant of papillary thyroid carcinoma (TCPTC) by the World Health Organization (WHO) have determined the inclusion of tumours with 30-49% of tall cells. However, the impact of tall cell percentage on papillary thyroid carcinoma (PTC) patients’ prognosis is still debated. We aimed to evaluate whether tall cell percentage affects patients’ outcome in the absence of aggressive features.
Methods
Rates of aggressive features, recurrence-free survival (RFS) and distant RFS (DRFS) (5-year median follow-up) were compared among tumours with less than 30%, 30-49% and at least 50% of tall cells. We also evaluated the impact of the new tall cell cut-off on patient management.
Results
Overall, 3092 tumours (15.7% of all PTC) were collected: 792 PTC had less than 30%, 503 had 30-49%, and 1797 had 50% or more tall cell areas. With the new definition of WHO, the number of TCPTC increased by 28%. There were no differences in recurrence rates according to tall cell percentage. The coexistence of BRAF and TERT promoter mutations predicted a worse RFS. Considering the new definition of TCPTC, the level of risk according to the American Thyroid Association increased from low to intermediate in 4.2% of cases. However, the recurrence rate within this subgroup was comparable to low-risk.
Conclusions
TCPTC and PTC with tall cell areas can be considered as a unique group with similar recurrence risk. However, whenever aggressive features are absent, tumors have a low risk of recurrence independently of tall cell percentage.
Risk of needing completion thyroidectomy for low‐risk papillary thyroid cancers treated by lobectomy
