The incidence of thyroid cancer has been rising worldwide, likely due to diagnostic advances in ultrasonography (US) and fine-needle aspiration (FNA) biopsy, which have improved the detection of subclinical thyroid cancers [1,2]. Much of this is attributable to well-differentiated thyroid cancer (WDTC), with papillary thyroid cancer (PTC) being the most common histological subtype, followed by follicular thyroid cancer [3]. The vast majority of thyroid cancers occur in the glandular lobes, while cancer of the isthmus reflects less than 3–9% of all cases [4,5]. The thyroid isthmus is a band of tissue that connects the lobes on either side from the 2nd to 4th tracheal cartilage rings. For patients with cancer confined to the isthmus, there is no clear consensus on the extent of thyroid resection and role of prophylactic central compartment dissection. Some studies have suggested that compared to cancer of the thyroid lobes, cancers of the isthmus tend to have more aggressive features, including a higher rate of extrathyroidal extension, capsular invasion, and lymph node metastasis [6,7]. The unique anatomic location, blood supply, and lymphatic drainage of the isthmus may be to blame, though this remains to be investigated [8].

The 2015 American Thyroid Association (ATA) guidelines provide no specific recommendations for the treatment of thyroid cancer confined to the isthmus [9]. ATA and the National Comprehensive Cancer Network (NCCN) guidelines indicate thyroid lobectomy as an appropriate initial treatment for tumors of the lobe that are 1–4 cm in size without extrathyroidal extension or lymph node metastasis. Total thyroidectomy is recommended in the setting of extrathyroidal extension or lymph node metastasis (LNM) [10]. It remains unclear if the paradigm of partial resection for low-risk cancers of the lobes can also be applied to cancers of the isthmus. Moreover, there are no randomized controlled trials assessing the noninferiority of isthmusectomy compared to total thyroidectomy. Encouragingly, isthmusectomy has shown potential as a safe and effective treatment strategy for WDTC confined to the isthmus throughout the literature. We therefore undertook a systematic review of the literature to assess the use of isthmusectomy as surgical management for well-differentiated thyroid carcinoma of the isthmus.