Squamous Cell Carcinoma Introduction and Overview

Summary Thoughts: Squamous Cell Carcinoma

Squamous cell carcinoma (SCCa) is, without question, the most common malignancy in the H&N. Recent developments in the understanding of the molecular nature and causes of SCCa now reveal it to be a heterogeneous malignancy.

In most sites of the H&N, tobacco is the most common causative agent in the development of mucosal dysplasia and neoplasia. Alcohol is a synergistic cofactor, while poor oral hygiene and genetics are also contributing risk factors. Paralleling the declining trend of smoking over the last 30 years, there has been an overall decline in the incidence of H&N SCCa, particularly in the oral cavity, larynx, and hypopharynx. Conversely, in the oropharynx there has been a rise in base of tongue (BOT) or lingual and palatine tonsillar SCCa , particularly in patients under 60 years, who may have a limited or no history of tobacco and alcohol use. This increasingly common group of SCCa tumors is positive for human papillomavirus (HPV), most commonly the HPV-16 subtype, which is also responsible for cervical and anogenital neoplasms. Currently in the United States, ~ 60% of oropharyngeal SCCa (especially tonsil and BOT) are due to HPV . HPV(+) SCCa appears to be more responsive to chemoradiation than HPV(-) SCCa, and patients have an overall better survival. Patients with HPV(+) tumors who are also smokers carry an intermediate prognosis.

Nasopharyngeal carcinoma (NPCa) is a distinctly different neoplasm with the most common histopathologic subtypes associated with Epstein-Barr virus infection. The least common and most aggressive form (keratinizing NPCa) is related to tobacco and alcohol abuse, although some pathology literature has also suggested an association with HPV infection.

While the current understanding of SCCa is evolving through greater molecular interrogation of these tumors, the clinicians' roles remain largely unchanged. At the time of diagnosis, the clinician must determine details about the primary tumor to assign a tumor stage , including the size and local extent of the primary, detecting perineural tumor (PNT), and assessing regional nodes and distant spread of disease. Following treatment, both baseline and surveillance imaging require careful evaluation to detect residual or recurrent SCCa , treatment complications , and 2nd primary neoplasms .