SECTION 11: PRECANCEROUS LESIONS AND CUTANEOUS CARCINOMAS

EPIDERMAL PRECANCERS AND CANCERS

Cutaneous epithelial cancers [nonmelanoma skin cancer (NMSC)] originate most commonly in the epidermal germinative keratinocytes or adnexal structures. The two principal NMSCs are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). SCC often has its origin in an identifiable in situ lesion that can be treated before frank invasion occurs. In contrast, in situ BCC is not known, but minimally invasive "superficial" BCCs are common.

The most common etiology of NMSC in fair-skinned individuals is sunlight, [ultraviolet radiation (UVR)], and human papillomavirus (HPV). Solar actinic keratoses are the most common precursor lesions of SCC in situ (SCCIS) and invasive SCC occurring at sites of chronic sun exposure in individuals of northern European heritage (see Section 10). UVR and HPV cause the spectrum of changes ranging from epithelial dysplasia to SCCIS to invasive SCC. Much less commonly, NMSC can be caused by ionizing radiation (arising in sites of chronic radiation damage), chronic inflammation, hydrocarbons (tar), and chronic ingestion of inorganic arsenic; these tumors can be much more aggressive than those associated with UVR or HPV. In the increasing population of immunosuppressed individuals (those with HIV/AIDS disease, solid organ transplant recipients, etc.), UVR- and HPV-induced SCCs are much more common and can be more aggressive.

ACTINIC KERATOSIS ICD-10: L57.0

• Single or multiple, discrete, dry, rough, or adherent scaly lesions on the habitually sun-exposed skin of adults, usually on a background of DHe.

• Actinic keratoses can progress to squamous cell carcinoma.

• Synonym: Solar keratosis.

EPIDEMIOLOGY

AGE OF ONSET Middle age, although in Australia and southwestern United States, solar keratoses may occur in persons <30 years.

SEX More common in males.

RACE SPT I, II, and III; rare in SPT IV; almost never in people with black skin.

OCCUPATION Outdoor workers (especially farmers, ranchers, and sailors) and outdoor sportspersons (tennis, golf, mountain climbing, and deep-sea fishing).

PATHOGENESIS

Prolonged and repeated solar exposure in susceptible persons (SPT I, II, and III) leads to cumulative damage to keratinocytes by the action of UVR, principally, if not exclusively, UVB (290 to 320 nm).

CLINICAL MANIFESTATION

SKIN SYMPTOMS Lesions may be tender. Painful if excoriated with a fingernail.

SKIN LESIONS Takes months to years to develop. Adherent hyperkeratotic scale, which is removed with difficulty and pain (Figs. 11-1 and 11-2). Skin-colored, yellow-brown, or a brown that appears "dirty"; often there is a reddish tinge. Rough, like coarse sandpaper, "better felt than seen" on palpation. Most commonly <1 cm, oval or round (Fig. 11-2).