Anaplastic thyroid carcinoma.

A 68-year-old man was referred to us with a 3- to 4-week history of progressive dysphagia for solids and a 1-week history of progressive dyspnea. He had initially presented to the emergency department alter becoming acutely short of breath. Physical examination identified a firm, nontender, fixed, right anterolateral neck mass. Subsequent imaging (figure) and biopsy identified the mass as an anaplastic thyroid carcinoma. A tracheostomy was performed, followed by combined radiochemotherapy as a palliative treatment. However, the patient died 6 months later from extensive lung metastasis.

Anaplastic thyroid carcinoma, also known as undifferentiated thyroid carcinoma, is the most aggressive thyroid malignancy. (1) While it represents only 2% of all thyroid malignancies, it accounts for 40% of all deaths from thyroid cancer. (2) At the time of presentation, distant metastasis to the lungs, bones, and/or brain has already occurred in 50% of patients. (2) The mean survival time is 6 months after diagnosis. (2) Death usually occurs as a result of local extension and airway compromise or complications from lung metastasis. (3)

Like differentiated thyroid carcinoma, anaplastic thyroid carcinoma is more common in women than men by a margin of 3:1. (1) Unlike other thyroid malignancies, anaplastic thyroid carcinoma usually presents at a late age--that is, in the 6th and 7th decades of life--and is thought to arise from differentiated thyroid carcinoma or multinodular goiter by thyroid-stimulating hormone transformation. (4) It is locally invasive, and it can cause dyspnea, hoarseness, and dysphagia secondary to involvement of, respectively, the larynx or trachea, the recurrent laryngeal nerve, and the esophagus. Physical findings include a firm thyroid mass (usually larger than 5 cm), vocal fold paralysis (30% of cases), and cervical lymphadenopathy (40%). (2) Previous head and neck radiation therapy is a predisposing risk factor. (2)

Computed tomography (CT) will show a diffusely infiltrative, heterogenously enhancing thyroid mass with variable degrees of necrosis and hemorrhage. The mass invades the surrounding structures of the visceral space and the infrahyoid neck with amorphous calcifications that may be present in 60% of cases. (1) T2-weighted magnetic resonance imaging (MRI) will show variable iso- to hyper-intensity with moderate to marked heterogenous contrast enhancement. (2) Radioactive iodine [sup.131] I scintigraphy will show a poorly defined cold nodule. (1) Chest x-rays may demonstrate a lung metastasis or a deviation or narrowing of the trachea. Contrast-enhanced CT can help determine the extent of the disease and the involvement of adjacent structures. However, the use of iodinated contrast may delay the administration of [sup.131]I therapy in patients who turn out to have differentiated thyroid carcinoma. MRI may be more sensitive than CT for evaluating the extent of the tumor in the neck and mediastinum. (2)

The differential diagnosis based on imaging includes differentiated thyroid carcinoma, multinodular goiter, follicular adenoma, medullary carcinoma, non-Hodgkin's lymphoma, and hemorrhagic colloid cyst. While invasive features, calcifications, and necrosis may suggest anaplastic thyroid carcinoma, a definitive diagnosis is made by clinical evaluation and biopsy.

Treatment is usually palliative, with a combination of radio- and chemotherapy and tracheostomy tube placement. Surgery is reserved for early tumors without significant extension or local invasion. (2)

References

(1.) Som PM, Curtin HD, eds. Head and Neck Imaging. 4th ed. St. Louis: Mosby; 2003:2156-7.

(2.) Harnsberger HR, Hudgins PA, Wiggins RH III, et al. Anaplastic thyroid carcinoma. In: Harnsberger HR, Hudgins PA, Wiggins RH III, et al, eds. Diagnostic Imaging: Head and Neck. Salt Lake City: Amirsys; 2004.

(3.) Konstantakos AK, Graham DJ. Thyroid, anaplastic carcinoma. Available at http://www.emedicine.com/med/topic2687.htm (access verified March 29, 2007).

(4.) Dahnert W. Radiology Review Manual. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2003:396.

Troy Hutchins, MD; Paul Friedlander, MD; Enrique Palacios, MD, FACR 

From the Department of Radiology (Dr. Hutchins and Dr. Palacios) and the Department of Otorhinolaryngology (Dr. Friedlander), Tulane University Medical Center, New Orleans.