Postoperatively determined high-risk histopathologic features in papillary thyroid carcinoma initially eligible for thyroid lobectomy: a game changer.

Purpose: Recent clinical practice guidelines consider thyroid lobectomy a viable alternative for low-risk papillary thyroid carcinoma PTC measuring 1-4 cm in size. We aimed to assess the likelihood of finding postoperatively determined high-risk histopathologic features that would lead to the recommendation of completion thyroidectomy.

Methods: A retrospective review of patients who underwent total thyroidectomy for PTC measuring 1-4 cm in size between Jan 2012 and Jan 2018 was conducted. Patients with pre-operative high-risk characteristics were excluded: history of radiation exposure, positive family history, clinically suspicious cervical lymphadenopathy, and gross extrathyroidal extension (ETE). A hypothetical group of 245 patients remained eligible for lobectomy. The pathology specimens from the cancer-containing lobes were evaluated for high-risk features: aggressive histology, capsular and/or vascular invasion, microscopic ETE, and multifocality. A subgroup analysis was performed with 2 cm being the cut-off size.

Results: The average age was 39 years with 73% being females. Mean cancer size was 16 mm. Evaluation of the cancer-containing lobe for high-risk features revealed: aggressive histology (33%), ETE (12%), capsular invasion (33%), vascular invasion (17%), and ipsilateral multifocality (30%). The cumulative risk of having ≥1 high-risk feature mandating completion thyroidectomy was 59%. The risk was considerably higher for lesions ≤2 cm compared to larger lesions (64% vs.48%; p = 0.049; RR = 1.3).

Conclusions: A considerable proportion of patients initially eligible for lobectomy have high-risk features that only become evident at pathology. Therefore, a comprehensive approach is advocated to determine the extent of surgery for PTC incorporating patient preferences regarding risks and benefits.