Individualizing Surgery in Papillary Thyroid Carcinoma Based on a Detailed Sonographic Assessment of Extrathyroidal Extension

Background: Lobectomy may be sufficient for patients with intrathyroidal papillary thyroid carcinomas (PTC) <4 cm without nodal metastasis. Based on the 2015 American Thyroid Association guidelines, a strategy using ultrasound to identify appropriate candidates for lobectomy was implemented.

Methods: Patients with Bethesda V or VI cytology who underwent surgery for PTC (January 2016 to May 2017) were retrospectively reviewed. Eligibility for lobectomy was based on both tumor (unilateral, intrathyroidal tumors ≤3 cm in size) and non-tumor (history of hypothyroidism, radiation exposure, etc.) characteristics. A detailed sonographic assessment of extrathyroidal extension (ETE) included surgeon-performed evaluation of thyroid capsular distortion, a long interface between tumor and thyroid capsule, irregular or indistinct tumor margins abutting the thyroid capsule, or a tracheal footprint.

Results: Of 141 patients with PTC, 35 (25%) patients were candidates for lobectomy, and 105 (75%) patients were not candidates for lobectomy because of non-tumor (n = 46) or tumor (n = 59) characteristics. Of the 35 patients who were candidates for lobectomy, 27 had sonographic ETE on detailed assessment. Total thyroidectomy was performed in 23 patients, while thyroid lobectomy was performed in 12 patients. Total thyroidectomy was indicated based on final histopathology in 15 patients (ETE, aggressive histology, vascular invasion, or cervical metastasis). Histopathologic ETE was present in 13 of these 15 patients and was the only indication for total thyroidectomy in the remaining eight patients. Positive and negative predictive values for the prediction of ETE based on detailed sonographic assessment were 52% and 100%, respectively. In comparison to a strategy of routine total thyroidectomy, a detailed sonographic assessment of ETE reduced the rate of potentially avoidable total thyroidectomy from 57% to 31%.

Conclusions: Patients with PTC who are potential candidates for lobectomy often require total thyroidectomy based on microscopic ETE detected on surgical pathology. A detailed sonographic assessment of ETE can reliably rule out microscopic ETE, reducing the rate of potentially avoidable total thyroidectomy.