Anaplastic Thyroid Carcinoma
Anaplastic Thyroid Carcinoma (ATC)
Anaplastic Thyroid Carcinoma (ATC) is the most advanced and aggressive thyroid cancer and is the least likely to respond to treatment. Even when diagnosis is established, surgery is less likely to provide any cure and chemotherapy or radiation is indicated. Fortunately, anaplastic thyroid carcinoma is rare and found in less than 1% of patients with thyroid cancer.
The diagnosis of ATC can often be suspected clinically, but pathological / histological tissue evaluation is mandatory to establish the diagnosis and to exclude other less aggressive and treatable entities that can mimic ATC. Diagnosis with fine-needle aspiration (FNA) biopsy may be diagnostic, but may be not always yield diagnostic material. In this case core biopsy or open biopsy may be needed. ATC has three main histological growth patterns: spindle cell pattern, pleomorphic giant cell pattern, and squamoid pattern. One of these patterns may predominate in a given tumor, or the tumor may show a mixture of two or three different patterns.
In addition to tissue diagnosis, cross-sectional imaging including neck ultrasound, CT scans or MRI (for the neck and chest), and PET/CT fusion scans should be used. All assessments that are required prior to primary treatment of ATC should be completed as rapidly as possible. Every patient should undergo initial evaluation of the vocal cords.
All anaplastic thyroid cancers are considered T4 tumors at the time of diagnosis.
T4a: The tumor is still within the thyroid.
T4b: The tumor has grown outside the thyroid.
NX: Regional (nearby) lymph nodes cannot be assessed.
N0: The cancer has not spread to nearby lymph nodes.
N1: The cancer has spread to nearby lymph nodes: N1a: The cancer has spread to lymph nodes around the thyroid in the neck (called pretracheal, paratracheal, and prelaryngeal lymph nodes); N1b: The cancer has spread to other lymph nodes in the neck (called cervical) or to lymph nodes behind the throat (retropharyngeal) or in the upper chest (superior mediastinal).
M0: There is no distant metastasis.
M1: The cancer has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc.
All anaplastic thyroid cancers are considered stage IV, reflecting the poor prognosis of this type of cancer.
Stage IVA (T4a, any N, M0): The tumor is still within the thyroid (T4a). It might or might not have spread to nearby lymph nodes (any N), but it has not spread to distant sites (M0).
Stage IVB (T4b, any N, M0): The tumor has grown outside the thyroid (T4b). It might or might not have spread to nearby lymph nodes (any N), but it has not spread to distant sites (M0).
Stage IVC (any T, any N, M1): The tumor might or might not have grown outside of the thyroid (any T). It might or might not have spread to nearby lymph nodes (any N). It has spread to distant sites (M1).
Current ATA Guidelines recommended that resectability of ATC should be determined by routine preoperative imaging studies (ultrasound, CT, MRI, and/or PET scan of the neck and chest). If locoregional disease is present and a grossly negative margin (R1 resection) can be achieved, surgical resection should be considered. In patients with systemic disease, resection of the primary tumor for palliation should be considered to avoid current or eventual airway or esophageal obstruction. Stage IVA/ IVB, resectable disease may benefit from a multimodal (surgery, IMRT for loco regional control, and systemic therapy) approach. A total lobectomy or total or near-total thyroidectomy with a therapeutic lymph node dissection should be performed in patients with intrathyroidal ATC. However, a majority of patients present with unresectable locoregional disease. Early palliative care involvement is inclusive of life-prolonging therapies. The sudden onset and explosive course of ATC necessitates immediate involvement by surgeons, radiation and medical oncologists, and palliative care teams.
Patients with stage IVA/IVB resectable disease have the best prognosis, particularly if a multimodal approach (surgery, radiation, systemic therapy) is used, and some stage IVB unresectable patients may respond to aggressive therapy. Patients with stage IVC disease should be considered for a clinical trial or hospice/palliative care, depending upon their preference.Patients with ATC have a median survival of 5 months and less than 20% survive 1 year. Early tumor dissemination results in 20-50% percent of patients having distant metastases and 90% having adjacent tissue invasion on presentation.
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