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Squamous Cell Carcinoma

Squamous cell cancer (SCC) arises in the epithelium and is common in the middle-aged and elderly population. Squamous cell cancers are often separated into two major groups based on their malignant potential. Those arising in areas of prior radiation or thermal injury, in chronic draining sinuses, and in chronic ulcers are typically aggressive and have a high frequency of metastasis. SCCs originating in actinically damaged skin are less aggressive and less likely to squamous cell cancer.

Risk factors.

UVB radiation is important for the induction of SCC. UVB radiation damages DNA.

Location.

Like basal cell cancer, squamous cell cancer is most common in sun-exposed areas; however, the distribution.

Incidence.

The incidence is highest in lower latitudes such as the southern United States and Australia.

Pathophysiology.

Atypical squamous cells originate in the epidermis from keratinocytes and proliferate indefinitely. A flat, scaly lesion becomes an indurated SCC when cells

LESIONS FROM WHICH SQUAMOUS CELL CARCINOMA ORIGINATES

Actinic keratosis
Cutaneous horn
Bowen's disease
Erythroplasia of Queyrat
Chemical exposure
Arsenic (internal)
Tar (external), except therapeutic tars
Leukoplakia
Lichen sclerosis et atrophicus (vulva)
Sites of chronic infection
Chronic sinus tracts
Osteomyelitis
Thermal burn scars (Marjolin's ulcer)
Radiation-damaged skin


penetrate the epidermal basement membrane and proliferate into the dermis.

Clinical manifestations.

SCCs arising from actinic keratosis may have a thick, adherent scale. The tumor is soft and freely movable and may have a red, inflamed base. These lesions are most frequently observed on the

Those SCCs beginning in actinically damaged skin, but not from actinic keratosis, appear as firm, movable, elevated masses with a sharply defined border and little surface scale. SCCs that arise in

Keratoacanthomas vs. SCC.

Keratoacanthomas are sometimes difficult to differentiate from SCC. Keratoacanthomas appear suddenly and grow rapidly (see p. 638). They reach a certain size, usually 0.5 cm to 2.0 cm, stop