39 Hypopharyngeal Carcinoma
The hypopharynx extends from the lower limit of the oropharynx at the level of the hyoid bone down to the lower level of the cricoid cartilage at the opening of the oesophagus. For the purposes of tumour classification, the UICC recognises three anatomical sites:
1. Post-cricoid (The pharyngo-oesophageal junction). Extends from the level of the arytenoid cartilages and connecting folds to the inferior margin of the cricoid cartilage, thus forming the anterior wall of the hypopharynx.
2. Piriform fossa This extends from the pharyngoepiglottic fold to the opening of the oesophagus. It is bounded medially by the arytenoids and aryepiglottic folds and laterally by the inner surface of the thyroid cartilage.
3. Posterior pharyngeal wall Extends from the superior aspect of the hyoid bone (floor of the vallecula) to the level of the inferior border of the cricoid cartilage.
More than 90% of tumours of the hypopharynx are squamous cell carcinomas. Other epithelial and mesodermal tumours of benign and malignant behaviour do occur, but they are rare.
Carcinoma of the hypopharynx is an uncommon disease with a prevalence of less than 1 per 100,000 population and constitutes 5 to 10% of upper aerodigestive tract malignancies. It is a disease of the elderly and the incidence is higher in men than in women. The post-cricoid site is unusual in that women have a higher incidence. Tobacco smoking and alcohol are the main aetiological agents. Approximately 2% of patients with the Paterson–Brown–Kelly syndrome (iron deficiency anaemia, glossitis, angular stomatitis, pharyngeal web, koilonychia and splenomegaly) will develop post-cricoid carcinoma. A few patients who had irradiation for thyrotoxicosis many years ago present with pharyngeal carcinoma after a latent period of over 30 years.
Hypopharyngeal tumours are sometimes so advanced when first seen that it is difficult to determine the site of origin, but the piriform fossa (60–70%) is the most common site, with posterior pharyngeal wall tumours (10–20%) and post-cricoid carcinoma (5–15%) occurring less often. Tumours of the posterior pharyngeal wall and the upper iriform fossa tend to be exophytic, whereas an ulcerated lesion is typical of the other parts of the hypopharynx. Tumours of the lateral wall of the piriform fossa may invade the thyrohyoid membrane and present as a palpable neck mass which may represent direct extension of the tumour rather than an enlarged lymph node. Medial wall tumours invade the aryepiglottic fold and into the paraglottic space, causing fixation of the vocal cord and consequent hoarseness. Dissemination of hypopharyngeal tumours in the submucosal lymphatics leads to a high incidence of ‘skip lesions’. Approximately 5 to 10% of patients have a second tumour in the oesophagus or lungs. Hypopharyngeal tumours also have a propensity to metastasise to cervical lymph nodes. The piriform fossa has the richest lymphatic drainage, around two-thirds of these patients will have lymph node metastases at presentation (level IV), with half of these being bilateral. Post-cricoid tumours tend to spread to paratracheal nodes (level VI). The incidence of distant metastases at presentation is higher than for any other head and neck cancer.
39.2 Clinical Features
Early symptoms include soreness, odynophagia, the sensation of a lump or discomfort in the throat. There may be referred otalgia via the auricular branch of the vagus nerve (Arnold’s or Alderman’s nerve). Later the patient will usually present with dysphagia, at first for solids then for fluids. Hoarseness may occur as a result of invasion of the larynx or vocal cord paralysis. The patient with advanced disease may have anorexia and weight loss. There may be a history of food sticking and repeated aspiration which will cause pneumonia. Determination of weight loss, comorbidity and performance status (Karnofsky or WHO) are essential as morbidity and mortality rates are higher in patients with poor parameters.
Fibre-optic laryngoscopy may reveal an obvious tumour or oedema of the arytenoids with pooling of saliva in the piriform fossa. A Valsalva manoeuvre can be useful to open the piriform fossae for a better view. There may be vocal cord fixation. The neck must be examined for lymph node metastases and occasionally a direct extension of the tumour through the thyrohyoid membrane is palpable as a neck mass. Laryngeal crepitus may be lost as the prevertebral fascia is invaded, particularly in post-cricoid tumours.
1. Laboratory tests: A full blood count to exclude anaemia and biochemical tests (U&Es and liver function tests [LFTs]) are required as electrolyte disturbances and malnutrition are not infrequent.
• For those patients who present with a neck mass, an ultrasound-guided fine-needle aspiration biopsy (USSgFNAB) will be the first investigation. This will help delineate the presence of nodal disease (enlarged nodes, round shape with loss of fatty hilum) and confirm squamous cell carcinoma (sensitivity and specificity over 90%).
• Contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) should be used to assess the extent of the disease. Scans should be performed prior to biopsy as this will distort the images and may affect staging and treatment discussions. The key determinants for staging and treatment are the site and size of the tumour, the tumour’s upper and lower limits, the presence of thyroid cartilage invasion, the possibility of prevertebral fascia invasion (likely to be considered inoperable and incurable) and the presence of cervical node metastases. MRI is preferable to CT scanning in delineating the soft tissue extent and spread of tumour but can overestimate thyroid cartilage invasion.
• A CT scan of the chest is mandatory to exclude metastases and may demonstrate any consolidation due to aspiration.
• A barium swallow can be used to help demonstrate the extent and limits of a hypo-pharyngeal tumour or oesophageal lesion.
• Positron emission tomography CT (PET-CT) is recommended for advanced hypopharyngeal cancers for assessment of the inferior extent of disease and in assessment of post-treatment residual disease or recurrence.
3. Endoscopy: Panendoscopy performed under general anaesthetic allows assessment of the tumour and a representative biopsy to be taken. Laryngoscopy and oesophagoscopy can evaluate the site, size and extent of the lesion, with the upper and lower limits (the distances will be measured on the endoscope from the upper incisors) particularly needing to be assessed. Bronchoscopy can be performed to look for spread to the trachea and oesophagoscopy may reveal skip lesions or a synchronous oesophageal primary, but the addition of bronchoscopy (to the so-called triple endoscopy of laryngoscopy and oesophagoscopy with bronchoscopy) is not mandatory, unless imaging is suspicious, as chest imaging is much improved. Digital examination of the tumour is appropriate if there is superior spread. Palpation of the patient’s neck while he or she is under the general anaesthetic allows further confirmation of nodal disease and assessment of mobility of the nodes.
39.4 Staging of Hypopharyngeal Carcinoma
When the patient has had a clinical assessment, radiological analysis and histological confirmation of squamous carcinoma, the UICC/AJCC stage should be conferred. Nodal stage is identical to that of the other head and neck subsites. The 8th edition UICC/AJCC primary site T stage for hypopharyngeal carcinoma is as follows:
Tumour limited to one subsite of hypo-pharynx and/or 2 cm or less in greatest dimension.
Tumour invades more than one subsite of hypopharynx or an adjacent site, or measures more than 2 but less than 4 cm in greatest dimension.
Tumour measures more than 4 cm in greatest dimension, or with fixation of the hemilarynx, or extension to the oesophagus.
Tumour invades any of the following: thyroid/cricoid cartilage, hyoid bone, thyroid gland, oesophagus or central compartment soft tissues (strap muscles or subcutaneous fat).
Tumour invades pre-vertebral fascia, encases carotid artery or involves mediastinal structures.
Stage grouping is based on the TNM status: