Oropharynx Carcinoma

Anatomy of Oropharynx

The oropharynx extends from the level of the hard palate superiorly to the level of the hyoid bone inferiorly, situated posterior to the oral cavity. The palatoglossal muscles (anterior pillars) demarcate the boundary between the oral cavity and the oropharynx, with the oropharyngeal isthmus forming the arched opening between the two left and right palatoglossal muscles. The palatopharyngeus muscles are present just posterior to the anterior pillars. The palatine tonsils reside in the tonsillar fossa between the palatoglossal and palatopharyngeus muscles in the lateral walls of the oropharynx. The oropharyngeal isthmus is bounded superiorly by the soft palate, inferiorly by the upper surface of the posterior third of the tongue, and laterally by the palatoglossal arch (anterior pillar).

Subsites of Oropharynx: Base of tongue, Tonsil and tonsillar fossa, Faucial arch and Pharyngeal wall

Boundaries of the Oropharynx

• Anterior Wall: Deficient superiorly and bounded by the anterior boundary of the palatoglossus muscles (anterior pillars), facilitating communication with the oral cavity. Inferiorly, it is formed by the posterior third of the tongue, containing lingual tonsils and valleculae. Valleculae are cup-shaped depressions between the base of the tongue and the anterior surface of the epiglottis, bounded medially by the median glossoepiglottic fold and laterally by the pharyngoepiglottic fold, and are prone to retention cysts.
• Posterior Wall: Related to the retropharyngeal space and lies opposite the second and upper part of the third cervical vertebrae.
• Lateral Wall: Formed by the anterior and posterior pillars and the palatine tonsils located between these pillars.
• Superior Wall: Composed of the soft palate.

Oropharyngeal cancer refers to malignancies occurring in the oropharynx, a region that includes the posterior one-third of the tongue, the tonsils, the soft palate, and the lateral and posterior pharyngeal walls. These cancers are often associated with significant morbidity and mortality, largely due to late diagnosis and the aggressive nature of the disease. Early detection and a comprehensive understanding of the risk factors, symptoms, and treatment options are essential for effective management.

Symptoms

The clinical presentation of oropharyngeal cancer can be subtle in the early stages, often delaying diagnosis. Common symptoms include:

• Sore Throat: Persistent throat pain that does not resolve with standard treatment.
• Odynophagia: Painful swallowing, which can become progressively worse.
• Dysphagia: Difficulty swallowing, often leading to weight loss and nutritional deficiencies.
• Voice Changes: Hoarseness or alterations in voice quality due to tumour involvement of vocal structures.
• Neck Mass: A palpable lump in the neck, often indicative of lymphatic spread.
• Referred Otalgia: Ear pain due to referred pain from the primary site of the tumour.
• Globus Sensation: A feeling of a lump in the throat.
• Trismus: Difficulty opening the mouth, often due to tumour invasion of the muscles of mastication.
• Dysarthria: Difficulty speaking, resulting from decreased tongue mobility or involvement of oral structures.
• Base of Tongue Mass: Detected on palpation, this is often a sign of advanced disease.

Risk Factors

• Smoking: A primary risk factor for squamous cell carcinoma of the oropharynx.
• Alcohol Abuse: Heavy alcohol consumption synergizes with smoking to significantly increase the risk.
• Tobacco Use: Including chewing tobacco, which is strongly linked to cancer of the oral cavity and oropharynx.
• Epstein-Barr Virus (EBV): Particularly associated with lymphoepitheliomas, a subtype of oropharyngeal cancer.

 

Malignant Tumours

Oropharyngeal malignancies can arise in various locations within the oropharynx, each with distinct pathological and clinical features. The common sites for malignancies include the posterior third of the tongue, the tonsils and tonsillar fossa, the faucial palatine arch (soft palate and anterior pillar), and the posterior and lateral pharyngeal walls.

Gross Appearances of Tumours. Malignant tumours in the oropharynx can be categorized into four gross morphological types:

1. Superficially Spreading Tumours: These are often located in the palatine arch and are rarely associated with metastasis.
2. Exophytic Tumours: These tumours protrude into the oropharyngeal cavity and are also typically found in the palatine arch. They have a low rate of metastasis.
3. Ulcerative Tumours: Commonly located at the base of the tongue and tonsils, these tumours have a poor prognosis due to their tendency to invade deep tissues and metastasize regionally.
4. Infiltrative Tumours: Similar to ulcerative tumours, these invade deeply and have a high likelihood of regional and distant metastasis.

Histological Types

1. Squamous Cell Carcinoma (SCC): This is the most common type of oropharyngeal cancer, accounting for over 90% of cases. SCCs vary in their degree of differentiation and can arise in multiple locations within the oropharynx:
   • Tonsil/Lateral Wall: 60% of cases
   • Base of Tongue: 25% of cases
   • Soft Palate: 10% of cases
   • Posterior Wall: 5% of cases

2. Lymphoepithelioma: A poorly differentiated variant of squamous cell carcinoma, often associated with EBV. It is typically found in the tonsils, base of the tongue, and vallecula. These tumours are radiosensitive.
3. Adenocarcinoma: These arise from minor salivary glands, most commonly found in the palate and faucial arches.
4. Lymphomas: These consist almost entirely of non-Hodgkin’s lymphomas. Both Hodgkin and non-Hodgkin lymphomas can originate from the tonsils and the base of the tongue, often presenting in younger patients. Cervical lymphadenopathy is a common presenting feature.
5. Minor Salivary Gland Tumours: Most minor salivary gland tumours in the soft palate are benign pleomorphic adenomas. However, in other parts of the oropharynx, malignant forms like adenoid cystic carcinoma and mucoepidermoid carcinoma are more common.
6. Other Types: Sarcomas and metastatic diseases, although rare, can also occur in the oropharynx.

Treatment Options of Oropharyngeal carcinoma. The management of oropharyngeal cancer is multidisciplinary, with treatment strategies tailored to the individual patient’s disease stage, tumour location, and overall health. The main treatment modalities include:

1. Surgery Alone: Surgical excision is often used for localized tumours, particularly in early-stage disease.
2. Radiation Therapy Alone: This is commonly used for tumours that are radiosensitive or in patients who are not surgical candidates.
3. Combination of Surgery and Radiotherapy: This approach is often employed for advanced tumours to maximize local control and survival.
4. Chemotherapy: Chemotherapy may be used as a primary treatment, in combination with radiation, or as an adjunct to surgery in cases of advanced disease.
5. Palliative Therapy: For patients with advanced, unresectable disease, or poor performance status, palliative care focuses on symptom management and quality of life.

Carcinoma of the Posterior One-Third or Base of Tongue

This type of carcinoma is relatively common, especially in regions like India. It often goes unnoticed until it has metastasized to cervical lymph nodes. Early symptoms can include a sore throat, a sensation of a lump in the throat, and mild discomfort during swallowing. As the disease progresses, symptoms such as ear pain, dysphagia, bleeding, and speech changes may develop.

Spread:

1. Local: The tumour may deeply infiltrate the tongue musculature, epiglottis, pre-epiglottic space, tonsils, and hypopharynx.
2. Lymphatic: Cervical node metastases are present in about 70% of cases at diagnosis, frequently involving jugulodigastric nodes.
3. Distant: Common sites of distant metastasis include bones, liver, and lungs.

Diagnosis: Indirect laryngoscopy may reveal the tumour, but palpation under anaesthesia often provides a more accurate assessment of the extent of infiltration. Imaging studies, such as a CT scan, are crucial for staging, and a biopsy is necessary for a definitive diagnosis.

Treatment: Treatment varies depending on the centre and may include radiotherapy, surgery, or a combination of both. Early-stage tumours (T1 and T2) with limited nodal involvement are often treated with surgery and possibly postoperative radiation. Advanced tumours (T3 and T4) generally require extensive surgical resection, including mandibular resection, neck dissection, and postoperative radiation. In cases where the disease is very advanced and the patient’s general health is poor, palliative treatment is the primary option.

 

Carcinoma of the Tonsil and Tonsillar Fossa

Squamous cell carcinoma is the most common malignancy in the tonsils. It often presents as an ulcerated lesion with a necrotic base. Lymphomas can also occur in the tonsils, presenting as unilateral enlargement, sometimes mimicking a peritonsillar abscess.

Spread:

1. Local: The tumour may extend to the soft palate, anterior and posterior pillars, base of the tongue, pharyngeal wall, and hypopharynx. Invasion of the pterygoid muscles and mandible may lead to pain and trismus. The parapharyngeal space may also be involved.
2. Lymphatic: Approximately 50% of patients have cervical node involvement at presentation.
3. Distant: Distant metastases occur in advanced cases.

Clinical Features: Patients often present with a persistent sore throat, difficulty swallowing, ear pain, and a neck lump. In advanced cases, symptoms like bleeding, foul breath, and trismus may occur.

Diagnosis: Physical examination, including palpation of the tonsillar area, is crucial for assessing the tumour’s extent. A biopsy is necessary for histological confirmation.

Treatment: Early-stage, radiosensitive tumours are typically treated with radiotherapy, including irradiation of the cervical nodes. For larger tumours, wide surgical excision, often involving hemimandibulectomy and neck dissection, is required. Combined therapy, which may include chemotherapy, is often employed for advanced cases.

 

Carcinoma of the Faucial (Palatine) Arch

These carcinomas are usually of the squamous cell type and involve the soft palate, uvula, and anterior tonsillar pillar. They tend to spread superficially and are generally well-differentiated, with a lower tendency for early nodal metastasis.

Spread: Local spread to adjacent structures and lymph nodes, particularly the upper deep cervical and submandibular nodes, is common.

Clinical Features: Patients typically report a persistent sore throat, localized pain, or earache. The tumour may be discovered during a routine examination.

Treatment: The primary treatment is either irradiation or surgical excision, depending on the tumour’s size and location.

 

Carcinoma of the Posterior and Lateral Pharyngeal Wall

These carcinomas often remain asymptomatic until they have spread submucosally to adjacent structures such as the tonsil, soft palate, tongue, nasopharynx, or hypopharynx. They may invade the parapharyngeal space or anterior spinal ligaments. Lymph node metastases are present in 60% of cases, often involving bilateral nodes.

Treatment: The preferred treatment is irradiation or surgical excision, often combined with block dissection when nodes are palpable. Access to the posterior pharyngeal wall is typically achieved through lateral pharyngotomy, sometimes requiring mandibular osteotomy for better access.

——– End of the chapter ——–

Learning resources.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Stell and Maran’s, Textbook of Head and Neck Surgery and Oncology
• R. Pasha, Otolaryngology-Head &Neck Surgery
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
   

  Author:

  

  Dr. Rahul Bagla
  MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
  Fellow Rhinoplasty & Facial Plastic Surgery.
  Renowned Teaching Faculty
  Mail: msrahulbagla@gmail.com
  India

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