Tumour size predicts risk of recurrence in tall cell subtype papillary thyroid carcinoma

Background: The tall cell subtype of papillary thyroid cancer (TCPTC) is the most common aggressive subtype and often treated aggressively. This approach may not be necessary in smaller tumours without adverse histological characteristics. Methods: 97 patients with TCPTC defined as a height-to-width ratio of >= 3:1 and at least 30% tall cells were compared against 390 classical papillary thyroid carcinoma (CPTC) based on tumour size with recurrence free survival (RFS) as the primary outcome. Results: TCPTC are more likely to present with adverse histological characteristics. In smaller tumours (<2 cm), only central lymph node metastasis (HR7.16 p = 0.03) and multifocality (HR10.11 p = 0.026) increased recurrence risk. In larger tumours, TCPTC histology (HR3.78 p = 0.002), lymphovascular invasion (HR3.02 p = 0.014) and central lymph node metastasis (HR3.24 p < 0.001) significantly increased recurrence risk. Conclusion: TCPTC tumours <2 cm without central lymph node metastasis and multifocality are similar in risk of recurrence to classical PTC and could be managed with lobectomy.