HYPOPHARYNX: MALIGNANT TUMORS
- Computed tomograhy and magnetic resonance imaging are important tools for establishing the extent of the primary tumor, especially in the postcricoid and esophageal verge areas.
- Computed tomography and magnetic resonance imaging are important tools for establishing the extent of cervical and retropharyngeal lymph node metastases.
- These factors help to determine optimal treatment strategies.
- Used judiciously, fluorine-18 2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) can further aid this diagnostic process.
- Surveillance imaging can be by a combination of anatomic and/or radionuclide imaging.
The basic staging and medical decision-making procedures for hypopharyngeal cancer include indirect laryngoscopy, direct laryngoscopy with biopsy, contrast-enhanced computed tomography (CECT) or contrast-enhanced magnetic resonance (CEMR) depending on the practice preference, and a chest x-ray. The imaging studies are essential in this clinical-diagnostic evaluation, providing unique and often pivotal information. Imaging provides additional information concerning the deep extent and regional spread of disease. Chest computed tomography (CT) and FDG-PET are necessary in selected cases.
This chapter describes the important role of diagnostic imaging in clinical decision making for hypopharyngeal cancer. Squamous cell carcinoma (SCCA) will be discussed in the first section and the less common malignant tumors in the second section.
A thorough knowledge of the following anatomy and anatomic variations of normal in each of the these areas is required for the evaluation of hypopharyngeal malignant tumors. This anatomy is presented in detail with the introductory material on the larynx, hypopharynx, cervical esophagus, and infrahyoid neck in general:
Primary Site Evaluation
- With regard to the hypopharynx and esophagus, knowledge of the detailed relationship of the hypopharynx to the larynx and pyriform sinus apex region is required. The relationship of the postcricoid region and esophageal verge must be completely understood. As well, the relationship of the postcricoid region and the upper cervical esophagus to the upper trachea and thyroid gland is important adjunctive information (Chapters 201, 209, and 221).
- With regard to the larynx, the relationship of mucosal landmarks and functional structures of the larynx to the hypopharynx is critical knowledge for assessing tumor spread in this region. This fund of knowledge must include the detailed anatomy of the laryngeal skeleton and its normal variations as well as the paraglottic space (PGS) and pre-epiglottic space (PES) relationships to the hypopharynx (Chapters 149, 201, and 221).
- Tongue base region and low oropharyngeal wall (Chapter 190).
Evaluation of Extrapharyngeal Spread
- Visceral compartment of the neck, thyroid gland, trachea, and related fasciae (Chapter 149).
Evaluation of Regional Lymph Node Disease
- Detailed knowledge of normal node and perinodal morphology and the common drainage pathways of laryngeal cancer, which emphasizes nodal levels 2 through 6 (Chapters 149 and 159).
Evaluation of Perivascular and Perineural Spread
- Knowledge of the entire course of the vagus and recurrent laryngeal nerves on both sides and of the superior laryngeal neurovascular bundle (Chapter 201).
Techniques and Relevant Aspects
The hypopharynx is studied in essentially the same manner as the larynx for the evaluation of known cancer and masses of uncertain etiology. The principles of using these studies are reviewed in Chapters 201, 206, and 215. Specific problem-driven protocols for CT and magnetic resonance imaging (MRI) of the hypopharynx and larynx are presented in Appendixes A and B.
There is little or no use for ultrasound in studying hypopharyngeal cancer or masses of uncertain etiology. It is used in some practices to assess the risk of lymph node metastases.
The approach with radionuclide studies depends on the aim of the examination. Most of the current usage is limited to cancer evaluation with FDG-PET. This is discussed in more detail in conjunction with the larynx (Chapter 201).
Pros and Cons
Indications for Study in Potential Hypopharyngeal Cancers
Evaluation of the Primary Site and Regional Disease
Almost all hypopharyngeal carcinomas are studied with imaging. CT is usually the initial examination. The primary tumor and all cervical and retropharyngeal nodes must be studied. MRI is used most efficiently in a supplemental role as directed by CT findings to localized areas of interest, usually the lower extent of the tumor at the pyriform sinus apex, postcricoid region, and esophageal verge (Figs. 219.1–219.4).
All primary tumors must be evaluated for the extent of the hypopharyngeal spread of the primary; cartilage invasion; spread to adjacent structures including the larynx, oropharyngeal walls, trachea, and esophagus; and extrapharyngeal spread to the soft tissues of the neck (Figs. 219.1–219.4). The evaluation must also include a search for regional adenopathy (Fig. 219.5) and spread along neurovascular bundles at risk (Figs. 219.3 and 219.4). Finally, the risk of any acute adverse complication, such as rapidly progressive airway obstruction, should be anticipated.
There are several areas where CT or magnetic resonance (MR) images consistently provide better information than the endoscopic examination. These include sometimes entirely submucosal spread to the postcricoid region upper cervical esophagus (Figs. 219.6 and 219.7) and larynx including the PGS and PES, laryngeal cartilage invasion (Figs. 219.6 and 219.7), and spread to the extrapharyngeal soft tissue of the neck along several pathways including the superior laryngeal neurovascular bundle (Figs. 219.6–219.8). These imaging studies also allow tumor volumes that may reside in these deep spaces to be measured along with the more exophytic component (Fig. 219.8F–H).
MRI strengths related to soft tissue contrast resolution may be exploited to help in making critical management decisions. In the hypopharynx, MR is most often used to study lesions that on CT are suspicious for submucosal spread within the postcricoid region that threaten spread toward or involve the esophageal verge (Figs. 219.7 and 219.9). This information is critical to surgical planning. A significant proportion of MR studies used to more generally evaluate hypopharyngeal cancer will be of poor quality owing to motion artifacts.
Detection of Recurrent Tumor
Diagnostic CT is the examination for detection of recurrence in the neck, study of the neopharynx, or the irradiated larynx and hypopharynx; in selected cases, FDG-PET may be useful. These issues are detailed more completely in the section on posttreatment surveillance that follows later in this chapter.
Evaluation of Hypopharyngeal and Laryngeal Dysfunction and Submucosal Masses
Some patients have SCCAs growing entirely beneath intact mucosa. The can cause vocal cord or swallowing dysfunction. Rarely, these tumors may arise out of sight of the endoscopist in the pyriform sinus apex or postcricoid region (Fig. 219.6) and grow anteriorly into the PGS. Submucosal masses are rarely caused by other submucosal tumors, such as minor salivary and benign mesenchymal tumors, and cannot be distinguished from squamous cell cancers. These may actually present first as a palpable neck mass. A rare paraganglioma might be anticipated when a mass bulging from the medial pyriform sinus wall shows intense vascularity and an enlarged superior laryngeal vascular bundle (Fig. 218.5). About half of all submucosal laryngeal masses will be a laryngocele (Chapter 203) that can mimic a submucosal mass arising along the lateral and or medial wall of the pyriform sinus. The presence of a laryngocele always requires a search for an obstructing primary tumor (Figs. 203.3 and 203.6). Deformity of the laryngeal skeleton due to old trauma or developmental variations may cause hypopharyngeal dysfunction and a mucosal bulge in the parapharyngeal space and pyriform sinus region that is readily recognized on CT or MR images. These conditions are discussed in more detail elsewhere (Chapters 150, 203, 205, and 207).
CT and MR vastly improve the clinical detection of subtle cartilage invasion. A thin (,3 mm) slice thickness is preferred for this task so that CT is likely the better choice as the primary examination. Some reports suggest that MR is better than CT for detection of early cartilage invasion. CT and MR are both imperfect in detecting early macroinvasion and, of course by definition, cannot directly show micro invasion. This issue is discussed in detail with regard to laryngeal cancer (Chapter 206).
FDG-PET for Staging and Other Indications
In most hypopharyngeal neoplasms, FDG-PET has a limited primary role, as this technique does not allow one to reliably assess the anatomic extent of the lesion and the possible invasion of the tumor into adjacent structures. Its value in determining or planning a more accurate gross target volume (GTV) for radiotherapy (RT), planning in hypopharyngeal cancer remains unproven with regard to it providing some incremental survival benefit (Chapter 5).
FDG-PET can detect neck nodal metastasis with a relatively high accuracy, but both false-positive and false-negative results occur. Although FDG-PET sometimes detects nodal metastasis missed by other imaging techniques, the high cost of this technique does not warrant its routine use for this indication since the nodes on both sides must be included in all treatment plans. Anatomic imaging will aid the initial treatment planning strategy more than FDG-PET data in patients with advanced neck disease.
In patients with advanced hypopharyngeal cancer, FDG-PET is useful to detect distant metastases and to exclude coincident primary tumors outside the head and neck region.
This technique must be used with discernment rather than applied indiscriminately for diagnosis and staging given its expense and often low potential to truly alter management decisions or have a measurable survival benefit.
Some investigators suggest that high fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) uptake may be a useful parameter for identifying aggressive tumors. Patients with a high standard uptake value (SUV) appear to be more resistant to the effects of RT with or without chemotherapy.1 A high SUV is also a negative predictive factor in patients primarily treated by surgery and postoperative RT.2 Currently, there is no agreement on how this information should be used in planning patient management. Also, specific SUV levels must be established at each institution. While trends related to SUV may apply across institutions, specific values related to trends are not necessarily transportable from one FDG-PET facility to another.
Hypopharyngeal Squamous Cell Carcinoma
Cancer of the hypopharynx is clearly linked to cigarette smoking and postcricoid cancer associated with the Plummer-Vinson syndrome; this is rarely seen in the United States and continental Europe but is more commonly encountered in the United Kingdom.3
Prevalence and Epidemiology
Hypopharyngeal cancer is about four times less common than laryngeal cancer. Hypopharyngeal cancer is mostly seen in the age group between 50 and 70 years. About 71% arises in the pyriform sinus, 17% in the postcricoid region, and 12% on the posterior hypopharyngeal wall.4 This cancer is more prevalent in men than in women; only postcricoid cancer is more common in women because of the association with Plummer-Vinson syndrome, which occurs almost exclusively in women.5
Pharyngeal wall and pyriform sinus cancers usually present with sore throat. Unilateral sore throat is a particularly worrisome symptom since sore throat from pharyngitis is almost always bilateral. Dysphagia, sensation of foreign body in the throat, otalgia, bloody saliva, aspiration, and voice change are typically later findings associated with more advanced disease.
Hoarseness is usually not an early presenting symptom in patients with hypopharyngeal cancer. Changes in voice quality do occur. Dysphagia and referred otalgia (from the vagus to Arnold nerve) are common presenting complaints. In hypopharyngeal cancer, a neck mass due to metastatic adenopathy is a common presenting sign.
Physical examination is mainly done by rigid and flexible fiber-optic endoscopes. The physical examination should establish whether the vocal cord is mobile, paretic, or fixed. The exact relationship of tumor to the pyriform sinus, postcricoid region, and esophageal verge may be uncertain even after careful direct endoscopy.
Localized pain or tenderness to palpation over the thyroid lamina suggests gross invasion of the cartilage.
A palpable neck mass may occasionally be direct extension of the primary tumor rather than adenopathy. Imaging is essential for clarification of these issues.
Pathophysiology and Patterns of Disease
More than 95% of malignant hypopharyngeal tumors are SCCAs. There is a tendency for cancers in this region to show carcinoma in situ at and frequently as much as 5 to 10 mm below surgical margins and well beyond grossly obvious mucosal margins (Figs. 219.6, 219.9, and 219.10). Skip areas of carcinoma in situ may make it difficult to obtain clear margins.
Minor salivary gland tumors are rare. Adenoid cystic carcinoma is likely the most common of these rare epithelial carcinomas arising in the lower pharynx and tracheal junction region. Sarcomas, metastases, and lymphoma are even rarer.
Patterns of Spread
Generally, tumor growth in the hypopharynx is directed by existing natural anatomic barriers. A tumor margin may be infiltrative or have pushing, well-defined borders (Chapters 21 and 23). There is a tendency for tumor to remain, at least for a time, confined to its area of origin. However, there is no real anatomic barrier that restricts spread from one area to the next.
CT and MR are very useful for evaluating some specific growth patterns of interest in medical decision making. The majority of pyriform sinus carcinomas are advanced at presentation. Even cancers that appear to be relatively limited clinically will frequently have gross involvement of the laryngeal framework and show extralaryngeal spread when imaged (Figs. 219.6–219.10). There is often submucosal spread well beyond visible mucosal margins. Invasion of the laryngeal skeleton and extralaryngeal spread (Figs. 219.6 and 219.7) occurs mainly in pyriform sinus primary tumors.