Anaplastic thyroid carcinoma (ATC) is an undifferentiated tumor derived from the follicular epithelium, which is infrequent and extremely aggressive. It has an annual incidence rate of 1–2 cases per million inhabitants and represents 1%–2% of all thyroid cancers.1 However, despite its low incidence rate, ATC accounts for 20%–50% of all deaths associated with thyroid cancer.2 All patients with ATC are categorized according to the TNM system of the American Joint Committee on Cancer (AJCC) as stage IV.3 The 1-year survival rate after diagnosis is very low. In a study published in 2017 that included 1,288 patients with unresectable or incompletely resected ATC, the median survival was 2.3 mo, and only 11.3% and 6.6% of patients survived more than 1 or 2 years, respectively,4 although there are published case series describing a 10-year survival ranging between 3% and 10% in patients without metastatic disease.5, 6

ATC has a higher incidence rate in women. It generally manifests between the 6th and 7th decades of life, and unlike differentiated thyroid cancer, it is practically never diagnosed before the 3rd decade of life.7 Similarly, unlike thyroid lymphomas, the presence of autoimmune thyroid disease is not an associated risk factor for the development of ATC.7

It is essential to make the differential diagnosis of this entity with other rapidly growing masses in the anterior cervical region, such as thyroid lymphoma, sarcoma, squamous cell carcinoma of the larynx, or pathological lymph nodes due to aggressive neoplasms of the aerodigestive tract, since these conditions have different therapeutic approaches.

The management of ATC requires a multidisciplinary team to assess therapeutic options, as well as the risks and benefits of different treatments. Although it is an oncological emergency, there are not many published series of ATC in the literature. Despite advances in the treatment of other oncological processes, the prognosis of ATC remains bleak and justifies research to focus on this disease. The objective of this work is to present our experience with the clinical presentation, diagnosis, management, and survival of ATC in the hospitals of the Public Health Service of Castilla-La Mancha (SESCAM), Spain.