Noninvasive anaplastic thyroid carcinoma: report of a case and literature review.

Anaplastic thyroid carcinoma (ATC) is an uncommon thyroid malignancy. Noninvasive ATC is a rare, surgically resectable variant with only four reported cases. We report a case of an 81-year-old man who presented with a 3.1 cm right thyroid lobe mass that on fine-needle aspiration biopsy was diagnosed as an ATC. Preoperative imaging revealed an encapsulated thyroid tumor without evidence of invasion of surrounding structures and no locoregional and distant metastases. A total thyroidectomy was performed that by histologic and immunohistochemical evaluation was diagnostic for a noninvasive ATC. Given the diagnosis of noninvasive ATC, adjuvant therapy was not administered. At 14 months following diagnosis, the patient remains disease free based on positron emission tomography/computed tomography imaging. A review of the outcomes of similar cases reported in the literature, as well as observations from our case, suggest a favorable prognosis for patients with noninvasive ATC. Noninvasive ATC may represent a distinct subset of resectable ATCs with an improved prognosis. The recently published American Thyroid Association (ATA) Guidelines for Management of Patients with ATC do not include this specific form of ATC. We encourage other authors to report similar cases in order to determine whether noninvasive ATC should be considered as a separate disease entity from the traditional highly lethal form of ATC.