ATC presents as a rapidly enlarging neck mass (Figure 4-1). The rate of growth is one of the fastest of all neoplasms; it is not unusual to see the masses double in size in a matter of days. The lesions are typically firm and large. Over 80% of ATC masses are larger than 5 cm on initial presentation.9 As the tumor grows rapidly, it can outgrow its blood supply, and the resulting necrotic areas can feel fluctuant in an otherwise firm background. The tumor cells may infiltrate the skin and cause overlying necrosis. More than 40% of patients present with associated adenopathy in other areas of the neck.3,5,9 The tumor has a tendency to invade the vital structures of the neck and to not respect tissue planes (Figure 4-2). Up to 30% of patients can present with hoarseness owing to vocal cord paralysis following tumor involvement of the recurrent laryngeal nerve.3,5,9 They can also present with dyspnea owing to airway
compromise following tracheal or laryngeal invasion. ATC invasion of the superior vena cava (SVC) can result in obstruction of the SVC (Figure 4-3). Patients with SVC syndrome present with upper body, face, and neck plethora. They also show signs of neck, chest, and upper extremity vascular congestion causing edema and prominent superficial venous engorgement. If the tumor mass invades the
esophagus, patients can experience dysphagia. The rapid growth rate can result in significant pain owing to invasion into nerves or muscles. Occasionally, ATC masses can present with leukocytosis that results from independent production of granulocyte colony-stimulating factor.
ATC is diagnosed with a tissue biopsy. Fine-needle aspirations tend to yield an accurate diagnosis; there can be false-negative or nondiagnostic results if the sample is obtained from an area of inflammatory or fibrotic reaction or from an area of hemorrhage. Several passes or the use of larger-core needles may be necessary. Rarely, one may need to carry out an incisional biopsy to obtain enough tissue for accurate classification. Unlike WDTC, there is usually no role for radioactive iodine scanning in
ATC. The use of serum markers is also of limited value because ATC cells do not secrete thryoglobu-lin, calcitonin, or carcinoembryonic antigen (CEA). In fact, the presence of an elevated CEA level and an elevated calcitonin level would suggest that the tumor is more likely to be a poorly differentiated medullary carcinoma of the thyroid. The presence of an elevated CEA without elevated calcitonin may be seen in a metastatic neoplasm involving the thyroid. Both of these entities may have a better prognosis than ATC so that accuracy in diagnosis is quite important. In younger patients, it is crucial to exclude tumors with much better prognosis. Young patients who present with poorly differentiated tumors should have their serum checked for the presence of a-fetoprotein and human chorionic gonadotropin (PhCG), which would suggest that one is dealing with a poorly differentiated germ cell tumor, quite curable, rather than with an incurable ATC.
Imaging studies are helpful in assessing the extent of disease. Magnetic resonance imaging (MRI) is particularly helpful in the neck (Figure 4-4) and brain. Computed tomography provides more information for the lungs and mediastinum (Figure 4-5). The scans can help assess the extent of disease to help define anatomic planes in anticipation of surgery or radiation. ATC is a systemic disease, with 50% of patients presenting with distant metastases. At least 80% of these patients will present with clinically evident pulmonary metastases, 15% of patients can present with bone metastases, and 13% with brain metastases.10 Distant metastases to the adrenals are seen in 33% and to intra-abdominal lymph nodes in 17%.210 Autopsy studies have shown that metastases are microscopically present in many patients, even when the imaging tests have been negative. One autopsy series showed pulmonary metastases in 100%, bone metastases in 80%, invasion of adjacent cervical soft tissues in 60%, and tracheal invasion in 27%.11 MRI of the brain can detect the presence of occult brain metastases and should be performed as part of the initial staging procedure. Bone scans are also valuable to confirm the presence of metastases in vulnerable weight-bearing areas, whether or not patients have actual symptoms. Positron emission tomography is gaining acceptance as a staging modality; its true value remains to be fully established. Staging procedures help determine the extent of disease, which, in turn, leads to early intervention. Although not curative, radiation to the brain or to bones affected with metastases can help preserve function and quality of life while avoiding seizures or catastrophic fractures.
The staging system in ATC is quite simple. The American Joint Committee on Cancer (AJCC) automatically classifies all patients with a histologic diagnosis of ATC as stage IV12 All ATC tumors are considered T4. They are further divided into T4a (confined to the thyroid, surgically resectable) and T4b (extending beyond the thyroid, surgically unresectable). Stage grouping is listed in Table 4-1.
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