Squamous Cell Carcinoma
Arising from keratinizing epidermal cells, squamous cell carcinoma of the skin is an invasive tumor with potential for metastasis. It occurs most commonly in fair-skinned white males older than age 60. Outdoor employment and residence in a sunny, warm climate (southern United States and Australia, for example) greatly increase the risk of squamous cell carcinoma.
Lesions on sun-damaged skin tend to be less invasive with less tendency to metastasize than lesions on unexposed skin. Notable exceptions are squamous cell lesions on the lower lip and the ears; almost invariably, these are markedly invasive metastatic lesions with a poor prognosis.
Causes
Predisposing factors associated with squamous cell carcinoma include overexposure to the sun’s ultraviolet rays, X-ray therapy, ingestion of herbicides containing arsenic, chronic skin irritation and inflammation, exposure to local carcinogens (such as tar and oil), hereditary diseases (such as xeroderma pigmentosum and albinism), and the presence of premalignant lesions (such as actinic keratosis or Bowen’s disease).
Rarely, squamous cell carcinoma may develop on the site of smallpox vaccination, psoriasis, or chronic discoid lupus erythematosus.
Transformation from a premalignant lesion to squamous cell carcinoma may begin with induration and inflammation of the preexisting lesion. When squamous cell carcinoma arises from normal skin, the nodule grows slowly on a firm, indurated base. If untreated, this nodule eventually ulcerates and invades underlying tissues.
Complications
Lymph node involvement and visceral metastasis, resulting in respiratory problems, are possible complications from disease progression.
Assessment
The patient history may disclose areas of chronic ulceration, especially on sunexposed skin.
Inspection may reveal lesions on the face, ears, and dorsa of the hands and forearms and on other sun-exposed skin areas. The lesions may appear scaly and keratotic with raised, irregular borders. In late disease, the lesions grow outward (exophytic), are friable, and tend toward chronic crusting.
As the disease progresses and metastasizes to the regional lymph nodes, the patient may complain of pain and malaise. He may also complain of anorexia and resulting fatigue and weakness.
Diagnostic tests
An excisional biopsy provides definitive diagnosis of squamous cell carcinoma. Appropriate laboratory tests depend on systemic symptoms.
