Head and neck squamous cell carcinomas (HNSCC) refer to SCCs of the aerodigestive tract of the head and neck rather than cutaneous SCCs. SCC is the most common tumour of the mucosa of the upper aerodigestive tract, and can occur anywhere there is squamous cell mucosa.
Epidemiology, risk factors, and general principles are similar irrespective of location and are thus discussed below. Clinical presentation, radiographic features, staging, and differential diagnoses are site-specific and are therefore discusses separately, with only general principles discussed below:
- sinonasal squamous cell carcinoma
- nasopharyngeal carcinoma
- oral cavity squamous cell carcinoma
- oropharyngeal squamous cell carcinoma
- hypopharyngeal squamous cell carcinoma
- laryngeal squamous cell carcinoma
Patients are typically elderly men, with a peak incidence between 50-70 years of age. The exception to this rule are patients with Plummer-Vinson syndrome who are generally younger (30-50 years of age) and more frequently female 2.
Human papillomavirus (HPV) is increasingly being recognised as a potential risk factor for HNSCC, having been recognised for some time in squamous cell carcinoma of the cervix. Some types are more strongly implicated (e.g. types 16, 18 and 31). HPV-16 DNA has been isolated in up to 50% of oropharyngeal squamous cell carcinomas when their insertion into host cells results in deactivation of p53 and pRb, and overexpression of p16 1,5. HPV may be primarily responsible for up to 30% of oropharyngeal SCC, and 16% of hypopharyngeal SCC 1-2.
The most commonly implicated risk factors overall have historically been smoking tobacco and alcohol ingestion. Additional risk factors are being identified, including some strains of the human papillomavirus (HPV). Risk factors to be considered therefore include 1-2,4:
- tobacco smoking
- alcohol: not a carcinogen as such but rather acts as a promoter
- HPV (especially types 16, 18 and 31: see below)
- betel nut chewing
- severe gastro-oesophageal reflux
- poor dental/oral hygiene
- snuff/chewing tobacco
- tertiary syphilis
- dystrophic epidermolysis bullosa
- lichen planus
- dyskeratosis congenita
Radiology has a great deal to offer patients with HNSCC. As imaging findings are site specific, only general principles are described below. There are three main scenarios in which radiology is involved:
Patients suspected clinically of having a squamous cell carcinoma are most frequently initially imaged with CT, which should be performed with intravenous contrast.
In the setting of a patient presenting with a neck mass, ultrasound and ultrasound-guided final needle aspiration with cytology are invaluable.
MRI is also increasingly used, although availability in many regions is limited.
It is important to remember that direct visualisation with laryngoscopy is often able to identify thin superficial lesions that are inapparent on imaging 3.
Head and neck squamous cell carcinomas are staged using the TNM staging system, and each anatomic site has its own definitions. Radiology is essential in assessing all three components and thus dictating management.
Cervical lymph node levels have also been devised.
In instances where nodes are suspicious but not clearly involved, ultrasound-guided fine needle aspiration or FDG-PET may be used to clarify staging.
Imaging of patients who have undergone treatment is often challenging, as the combination of often extensive excisional and reconstructive surgery with superimposed radiotherapy distorts normal anatomy and alters tissue characteristics.
Additionally, a wide array of potential complications exist, including:
- breakdown of surgical repair, e.g. fistula formation
- radionecrosis, e.g. temporal lobe radionecrosis, mandibular osteoradionecrosis
Treatment and prognosis
Treatment is site-specific, but in general consists of surgical excision of the primary tumour, neck dissection of variable extent for lymph node assessment with or without radiotherapy.
Prognosis depends not only on staging but also on location (even corrected for stage). Hypopharyngeal squamous cell carcinoma fares most poorly, with a 5-year survival for stage I-II of only 47%, compared to, for example, laryngeal squamous cell carcinoma of similar stage which have a 5-year survival of 79% 1.
Another prognostic factor is p16 expression (as a surrogate for HPV infection), with p16-positive HNSCC having a better prognosis than p16-negative HNSCC 5.
- 1. Doherty GM. Current Diagnosis & Treatment Surgery. McGraw-Hill. (2010) ISBN:0071635157. Read it at Google Books - Find it at Amazon
- 2. Harrison LB, Sessions RB, Hong WK. Head and neck cancer, a multidisciplinary approach. Lippincott Williams & Wilkins. (2008) ISBN:0781771366. Read it at Google Books - Find it at Amazon
- 3. Lell MM, Gmelin C, Panknin C et-al. Thin-slice MDCT of the neck: impact on cancer staging. AJR Am J Roentgenol. 2008;190 (3): 785-9. doi:10.2214/AJR.07.3081 - Pubmed citation
- 4. Mafee MF, Valvassori GE, Becker M. Imaging of the head and neck. George Thieme Verlag. (2004) ISBN:1588900096. Read it at Google Books - Find it at Amazon
- 5. Langendijk JA, Psyrri A. The prognostic significance of p16 overexpression in oropharyngeal squamous cell carcinoma: implications for treatment strategies and future clinical studies. Ann. Oncol. 2010;21 (10): 1931-4. doi:10.1093/annonc/mdq439 - Pubmed citation