Other SCC lesions associated with more aggressive behavior include those that involve the lips, ears, anogenital region, or nerves; those that develop within a scar or chronic wound; those larger than 2 cm; those that have invaded the subcutaneous fat; those with poor differentiation; and those representing a recurrent disease.9 SCCs in the following locations are associated with high rates of metastasis: scalp, forehead, temple, eyelid, nose, dorsal surface of the hands, penis, and scrotum.8

Unlike BCC, SCC on an eyelid can invade the ocular nerve or the bone of the orbit, or can metastasize to more distant locations, to become fatal.10 Of clinical importance is squamous cell in situ (Bowen disease), a cancerous malignancy that will progresses to invasive SCC if left untreated. SCC in situ often appears as a pink or mildly scaly plaque, patch, or macule.

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An actinic keratosis (AK) is a common skin lesion that can progress to SCC. AKs can be subtle to obvious. They are often rough or scaly macules or plaques of pink, tan, or brown color. These lesions often wax and wane but rarely resolve on their own. AKs can be diagnosed clinically and treated, but because a clinical diagnosis can be wrong, patients should be followed for complete resolution of a treated AK.

A lesion identified as an AK that does not resolve may in fact be an SCC. A more definitive way to differentiate between an AK and SCC would be to biopsy the lesion.

Once an AK is diagnosed, treatment options include liquid nitrogen cryotherapy, photodynamic therapy, and topical prescription chemotherapy. Patients using topical prescription chemotherapeutic agents such as topical 5-fluorouracil, imiquimod cream, and ingenol mebutate (Picato) can expect to experience irritation, redness, swelling, and scabbing of the skin during cutaneous treatment of AK.

However, ingenol mebutate and other new topical agents require as few as 3 days of application, compared with up to 12 weeks of application required by some older medications, and the skin normally returns to baseline (the AK resolves, as does any inflammation or crusting) in 14 to 21 days.

Correctly identifying AK is important in terms of preventing SCC, which can have much more devastating treatment and life-expectancy outcomes.

Treatment. Uncomplicated, solitary, small lesions caught early can be treated with ED&C. However, excision or Mohs surgery excision are the more commonly used treatments due to the potentially aggressive nature of SCC. Chemotherapy or radiation therapy may be used adjunctively or for patients who are not surgical candidates. 

This article originally appeared on Clinical Advisor