Head and neck cancer

Head and neck cancer arises in the nasal cavity, paranasal sinuses, lips, mouth, salivary glands, throat, or larynx (voice box). Head and neck cancers are common in several regions of the world where tobacco usage and alcohol consumption is high. The age-standardized incidence rate in males exceeds 30/100,000 in regions of France, Hong Kong, the Indian subcontinent, Central and Eastern Europe, Spain, Italy, Brazil, and among US African Americans. High rates (>10/100,000) in females are found in the Indian subcontinent, Hong Kong and the Philippines. Of all newly diagnosed cancers, head and neck cancers comprise approximately 10% in the western world, but one third is in India. The variation in incidence by subsite of head and neck is mostly related to the relative distribution of major risk factors such as tobacco or betel quid chewing, cigarette or bidi smoking, and alcohol consumption.

Infection with cancer-causing viruses also contributes to cancer development. Cancer-causing types of human papillomavirus (HPV) are associated with cancer of the oropharynx and better prognosis in patients with advanced forms of cancer. A higher percentage of cancer in the oropharynx in the developed countries is attributed to HPV (up to 70% in the USA). Epstein-Barr virus plays important role in cancer development in the nasopharynx. Occupational exposure to wood or nickel dust or formaldehyde is a risk factor for cancers of the paranasal sinuses and nasal cavity. The occurrence of head and neck cancer in young adults and in non-users of tobacco and alcohol suggests that genetic predisposition may be a possible etiologic factor.

Most often, head and neck cancer show symptoms of a longstanding sore in the mouth or the throat, a lump in the neck, difficulty in swallowing, and a change or hoarseness in the voice.

Most head and neck cancers arise from the squamous epithelium and are squamous cell carcinomas of different histologic grades. The tumor cells in well-differentiated cancers closely resemble normal squamous epithelium, whereas poorly differentiated cancers are difficult to classify as being of squamous epithelial origin. Salivary gland tumors (mainly adenocarcinomas) comprise a minority of head and neck tumors. Squamous and salivary gland carcinomas spread by direct contiguity and by the lymphatic route draining into the regional lymph nodes.

For most head and neck tumors, diagnosis can be established by microscopic examination alone. Immunohistochemistry plays an important role in poorly differentiated tumors and in tumors with unusual morphological features. The most frequently used antibodies include cytokeratin (CK), p63, and S-100 (for the diagnosis of squamous cell carcinoma or salivary gland carcinomas). Routine evaluation of p16 expression is done on all oropharyngeal cancers, as a surrogate marker of HPV presence, bearing important information for the prognosis. Molecular studies are used in undifferentiated tumors for the evaluation of EBV presence or in salivary gland tumors for the evaluation of genetic alterations and confirmation of their subtypes.

The prognosis of patients with head and neck cancer varies among histological types and anatomic site. A 5-year survival is better in salivary gland cancer and cancers in the mouth, oropharynx, and larynx (around 60%) than in hypopharyngeal cancer (around 30%). The treatment of patients with head and neck cancer depends on a number of factors, including the location of the tumor, histological type, and the stage of cancer. Main treatment options include surgery and radiotherapy, as well as chemotherapy in advanced cases. Immunotherapy with checkpoint inhibitors may be an option in patients with squamous cell carcinoma.