Continuing medical educationCutaneous squamous cell carcinoma: Incidence, risk factors, diagnosis, and staging
Section snippets
Epidemiology and estimates of incidence
Key points Cutaneous squamous cell carcinoma is the second most common nonmelanoma skin cancer after basal cell carcinoma, and in some studies approaches the incidence of basal cell carcinoma The incidence of cutaneous squamous cell carcinoma is increasing yearly in the United States Estimates of mortality rates of cutaneous squamous cell carcinoma approximate that of renal and oropharyngeal carcinomas and melanoma in the southern and central United States
Cutaneous squamous cell carcinoma (cSCC) is the
Pathogenesis and etiologic risk factors
Key points Genes commonly mutated in patients with cutaneous squamous cell carcinoma include TP53, CDKN2A, Ras, and NOTCH1 Risk factors that predispose to the development of cutaneous squamous cell carcinoma include light skin (Fitzpatrick skin types I-III), age, male sex, exposure to sunlight or other ultraviolet radiation, immunosuppression, human papillomavirus, chronic scarring conditions, familial cancer syndromes, and environmental exposures, such as arsenic
Clinical and histopathologic diagnosis
Key points Histopathologic subtypes of cutaneous squamous cell carcinoma that are well-differentiated with low metastatic potential include keratoacanthoma and verrucous carcinoma This includes Buschke–Lowenstein tumors found in the genitalia and groin and epithelioma cuniculatum, which is found on the plantar surface of the foot Histopathologic subtypes of cutaneous squamous cell carcinoma with poor prognosis include desmoplastic cutaneous squamous cell carcinoma, adenosquamous cutaneous squamous cell
Factors associated with local recurrence and metastases
Key points Tumor diameter >2.0 cm is the risk factor most highly associated with disease-specific death Perineural involvement of nerves >0.1 mm in caliber is associated with increased nodal metastases and increased mortality risk
Lymph node metastases from head and neck cSCC have a high cure rate when identified and treated early.48, 49 Risk factors that predispose an individual to a higher rate of local recurrence and metastasis are discussed below.
Various classification schemes and clinical application
Key points The American Joint Committee on Cancer's (AJCC) most recent staging system, AJCC-8, published in October 2016, uses tumor diameter ≥2 cm as the distinguishing factor between T1 and T2 tumors High-risk features in AJCC-8 staging, which result in upstaging to T3, include tumor diameter ≥4 cm, minor bone erosion, invasion of nerves 0.1 mm in caliber or in subcutis, or deep invasion (≥6 mm or beyond the subcutaneous fat) T4 is reserved for major bone involvement or skull base invasion An alternative
AJCC-8
In October 2016, the AJCC introduced the 8th edition of its cancer staging systems. AJCC-8 includes a revision of the cSCC staging system, which was developed within the head and neck committee and therefore only applies to cSCCs located on head and neck skin and vermillion lip. It is not specified how cSCCs located elsewhere on the body are to be staged. The AJCC-8 staging system classifies cases by local tumor burden (T), nodal status (N), and metastatic disease (M). The T category is based
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Funding sources: None.
Dr Schmults was involved in the development of the Brigham and Women's tumor staging system for cutaneous squamous cell carcinoma. Drs Que and Zwald have no conflicts of interest to declare.
Reprints not available from the authors.
Date of release: February 2018
Expiration date: February 2021