Head and neck squamous cell carcinomas
Head and neck squamous cell carcinomas (HNSCC) refer to squamous cell carcinoma (SCC) of the aerodigestive tract of the head and neck, as opposed to cutaneous SCC. They are the most common tumor of the head and neck region, and can arise from any structure with squamous cell mucosa.
HNSCC is commonly categorized based on specific location, each with characteristic clinical presentation, radiographic features, staging, and differential diagnoses:
- sinonasal squamous cell carcinoma
- nasopharyngeal carcinoma
- oral cavity squamous cell carcinoma
- oropharyngeal squamous cell carcinoma
- hypopharyngeal squamous cell carcinoma
- laryngeal squamous cell carcinoma
All categories of HNSCC have similar risk factors, and histopathology irrespective of specific location, and will be discussed in this article.
The epidemiology of HNSCC is thought to be substantially impacted by behavioral and environmental risk factors. Since most large epidemiological studies are based on major cancer databases, reported statistics probably have significant geographic bias.
- overwhelmingly affecting males more commonly than females 6
- peak incidence between 50-70 years of age
- although overall low, a rising incidence of HNSCC in younger patients is increasingly recognized
- HSCC in the setting of Plummer-Vinson syndrome may present at a younger age (30-50 years of age) and more commonly in females 2
- by location - fluctuating incidence by anatomic location 6:
- decreasing overall incidence of oral cavity SCC
- increasing overall incidence of oropharyngeal SCC
- increasing overall incidence of oral tongue SCC
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 (including smokeless tobacco)
- 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-esophageal reflux
- poor dental/oral hygiene
- snuff/chewing tobacco
- tertiary syphilis
- dystrophic epidermolysis bullosa
- lichen planus
- dyskeratosis congenita
Human papillomavirus (HPV) is increasingly being recognized as a potential risk factor for HNSCC, having been recognized 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.
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 visualization 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
Posttreatment response assessment and surveillance is most commonly performed with contrast-enhanced CT, preferably with FDG PET at least at the first (baseline) exam. Standardized reporting templates in this setting have been proposed by the American College of Radiology (NI-RADS).
Treatment and prognosis
Treatment is site-specific, but in general consists of surgical excision of the primary tumor, 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
- 6. LeHew, Charles W, Weatherspoon, Darien J, Peterson, Caryn E, Goben, Abigail, Reitmajer, Karolina, Sroussi, Herve, Kaste, Linda M. The Health System and Policy Implications of Changing Epidemiology for Oral Cavity and Oropharyngeal Cancers in the United States From 1995 to 2016. (2017) Epidemiologic Reviews. 39 (1): 132. doi:10.1093/epirev/mxw001 - Pubmed