Malignant Tumors of the Base of Tongue Workup

• The standard initial evaluation for distant metastases includes a chest radiograph and serum chemistry studies.

  • Chest radiographs have an approximate sensitivity and specificity of 50% and 94%, respectively, for the detection of pulmonary metastases.
  • Elevated serum levels of alkaline phosphatase are highly specific for the presence of bone metastases, but the sensitivity is low (20%).
  • Although serum liver function tests assess hepatic function, abnormal values are found in almost half the patients with head and neck cancer because of chronic alcohol use and, therefore, are of little value in identifying patients with liver metastases during the initial assessment. Modest elevation of liver function test results does not always require further investigation to exclude hepatic metastases.
• In general, obtain a chest CT scan if the chest radiograph yields abnormal findings; obtain a bone scan if the alkaline phosphatase level is elevated or symptoms are present; and perform an ultrasound, CT scan, or MRI on the liver when liver function test results are significantly elevated, depending on tumor stage and associated comorbidities.

• Patients in whom a malignant neoplasm of the base of the tongue is suggested should undergo an imaging study as part of their evaluation to aid in accurate staging of the primary site and necks.

  • CT scanning with intravenous contrast has been the standard imaging technique since its introduction.
  • MRI offers the advantages of finer tissue detail and multiplanar views and should be considered the imaging test of choice.
  • Chest radiographs are useful as a screening test for metastatic disease or a second primary malignancy.
  • Ultrasound is used in some parts of the world to assess tumor thickness.
  • Positron emission tomography (PET) alone or in combination with MRI is helpful when the diagnosis is unclear, in cases of unknown primary malignancy, or as a pretreatment assessment prior to nonsurgical treatment.
  • PET scanning is a new imaging technique that provides absolute and comparable quantitative data on tumor metabolism before and after chemotherapy. Radiolabeled fluorodeoxyglucose is used to measure metabolic activity. As tumor cells consume more glucose relative to surrounding normal cells, a difference in signal intensity can be identified. The presence of PET activity correlates with pathologic findings in patients with head and neck cancer. Elevated or rising PET activity after radiation therapy strongly suggests persistent or recurrent disease that may not be detected by CT scan or MRI.
  • Patients with hypopharynx or cervical esophagus cancer who are candidates for chemoradiation protocols should undergo PET scanning as part of their preoperative evaluation.

Patients with underlying lung disease, such as chronic obstructive pulmonary disease or emphysema, should undergo pulmonary function testing, arterial blood gas, and consultation with a pulmonary medicine clinician prior to a final decision regarding treatment choice.

• The extent of disease at the primary site, the status of the lymph nodes in the neck, and the evaluation for metastatic disease are vital to appropriate treatment planning. Examining a biopsy specimen obtained via endoscopic examination of the primary site with the patient under anesthesia remains the definitive procedure to establish the diagnosis and accurately assess the primary tumor.
• The indications for routine panendoscopy for the detection of second primary malignancies have significant geographic variation that is not based on differences in patient or tumor characteristics. Substantial disagreement exists in the literature regarding the value of endoscopic screening for synchronous tumors. The prevalence rate of second primary malignancies of the upper aerodigestive tract varies from 3-15%, and most tumors are detected within 2 years of initial presentation. Second primary malignancies are more common in patients with hypopharynx and esophageal carcinoma relative to other head and neck sites.

  • A higher detection rate is reported for patients undergoing routine panendoscopy. Others recommend regular endoscopic intervention within 2 years of treatment for optimum detection of second primary cancers.
  • Critics of routine screening esophagoscopy and bronchoscopy point out the low yield, potential for increased morbidity, questionable impact on expected survival and outcome, and cost in support of their position.
  • The decision regarding routine panendoscopy in the evaluation of hypopharynx and cervical esophagus cancer is currently at the discretion of the clinician.

The most common histology finding in patients with malignant neoplasms of the base of the tongue is squamous cell carcinoma. The physical appearance of these lesions can be confused with benign lesions, such as necrotizing sialometaplasia and ectopic gastric mucosa. Other less common histologies include neuroendocrine carcinomas, extrapulmonary bronchogenic carcinoma, typical and atypical carcinoid tumors, adenocarcinoma and adenosquamous carcinoma, basosquamous carcinoma, and lymphoepithelioma. Malignant transformation of a thyroglossal duct cyst may involve the tongue base secondarily.

Perineural invasion; vascular invasion; positive nodal status; extracapsular spread; contralateral, bilateral, or fixed nodes; level 4 or 5 positive nodes; and N2 disease are all significant predictors of lower survival, a higher incidence of neck recurrence, greater risk of distant metastases, and a poorer outcome.

Extranodal non-Hodgkin lymphoma of the head and neck is a relatively uncommon disease. If the nasopharynx (16%), tonsil (12%), and base of the tongue (8%) are grouped together, this combined site (Waldeyer ring) becomes the most common site of disease (36%).^[3] Most Waldeyer ring lymphomas express the B-cell phenotype. The clinical features and immunohistological findings suggest that Waldeyer ring lymphomas, other than those of the nasopharynx, share some of the characteristics of mucosa-associated lymphoid tissue lymphomas.

In difficult cases, detection of monoclonal immunoglobulin, an absence of keratin staining, and a lack of epithelial features based on electron microscopy findings are useful adjuncts for diagnosis. Three fourths of the patients have stage I or II disease, and approximately two thirds of them have intermediate-grade lymphoma. Patients with lymphomas of high histopathologic grade and recurrent and disseminated disease have the poorest prognosis.

Other malignant histologies, including minor salivary gland cancer (eg, mucoepidermoid carcinoma, adenocarcinoma, adenoid cystic carcinoma), have been reported. Liposarcoma, leiomyosarcomas, and alveolar soft part sarcoma have been described in the base of tongue area, but these are rare.

Staging for malignant neoplasms of the base of tongue follows the guidelines described in the Manual for Staging of Cancer produced by the American Joint Committee on Cancer and is similar to staging of other subsites within the oropharynx. Staging of the primary site depends on the size of the lesion and the degree of involvement of adjacent structures. Note that staging of the neck for patients with malignant neoplasms of the base of the tongue is according to the American Joint Committee on Cancer criteria for tumors of the oropharynx.

• T1 - Tumor (T) smaller than 2 cm in greatest dimension
• T2 - Larger than 2 cm but smaller than 4 cm in greatest dimension
• T3 - Larger than 4 cm in greatest dimension
• T4 - Invades adjacent structures (eg, bone, soft tissue of neck, deep muscles of tongue)