Anaplastic thyroid cancer: prevalence, diagnosis and treatment.

UNLABELLED: Anaplastic thyroid cancer (ATC) is a rare aggressive tumor arising from the follicular cells of the thyroid gland (as does well differentiated thyroid cancer, WDTC), but ATC cells do not retain any of the biological features of the original follicular cells, such as uptake of iodine and synthesis of thyroglobulin. Prognosis is almost invariably fatal. In this article the Authors review the pathology, epidemiology, clinical presentation, diagnosis and treatment options of ATC. ATC incidence typically peaks at the 6-7th decade of life (mean age at diagnosis 55-65 years), women representing 55-77% of all patients. ATC represents 2-5% of all thyroid tumors, with a decreasing trend with respect to the incidence of WDTC. The histologic patterns of ATC include giant-cell, spindle-cell and squamoid-cell tumors; these subtypes frequently coexist and are not predictive of patients' outcome. Immuno-cyto-chemistry for thyroglobulin is usually negative or weakly positive and some cases are also negative for keratin, particularly in the spindle-cell areas. ATC may arise de novo, but in most cases it develops from a pre-existing WDTC, especially the follicular subtype. Most ATC patients complain of local compressive symptoms, such as dysphagia, dysphonia, stridor and dyspnea in addition to neck pain and tenderness; in over 70% of the patients the tumor infiltrates surrounding tissues, such as fat, trachea, muscle, esophagus, and larynx. The clinical course of a rapidly enlarging mass that is firm and fixed to surrounding structures in an elderly patient is quite suggestive for ATC. Diagnosis can be confirmed by fine needle aspiration cytology or, in doubtful cases, by histology on core biopsy. Computed tomography (CT) scan and magnetic resonance imaging (MRI) are useful for defining the local extent of disease and for identifying distant metastases, as is also positron-emission tomography (PET) with [(18)F]FDG. Tracheoscopy and esophagoscopy should be performed every two months, or whenever patients refer the appearance or worsening of local symptoms. Bone scintigraphy may be included in the follow-up of patients with a longer survival and relatively good health. Because of its aggressive behavior, the latest American Joint Committee on Cancer Staging Manual classifies all ATCs as T4 and Stage IV tumors, regardless of their actual overall tumor burden. Treatment of ATC has not been standardized because it is not clear whether or not therapy is effective in prolonging survival; most patients die within six momths from diagnosis, primarily because of asphyxiation caused by local tumor invasion. When employed alone, surgery, radiotherapy, or chemotherapy are seldom adequate to achieve overall control of the disease, but a combination of these treatments may improve local control. Surgical treatment of local disease offers the best opportunity for prolonged survival if the tumor is intrathyroidal. When the tumor is extrathyroidal, the surgical approach to ATC is controversial. Some favourable results have recently been reported with newly developed chemotherapy agents and hyper-fractioned radiation therapy. Tracheostomy should be performed in patients with impending airway obstruction when death is not imminent from other sites of disease, and if patients are not candidates for local resection or chemoradiation. Interventional bronchoscopy, including Nd-YAG laser and airways stenting are alternatives to surgery in inoperable ATC-induced tracheal obstruction. Gene therapy is under investigation. Although very rare, ATC is a highly aggressive tumor that belongs to the group of killer tumors with median survival time not longer than 6-8 months. Surgery, chemotherapy and radiotherapy are the conventional therapeutic strategies performed in the attempt to improve survival. Unfortunately, very often they do not succeed any clinical benefit but only palliative

RESULTS: New therapeutic strategies based on molecular approaches are desirable.