Lesion	Location	Surface	Color	Outline	Other features
Squamous cell carcinoma	Areas exposed to sunlight, radiation or arsenicals	Rough, irregular, sometimes scaly, sometimes has visible vessels, sometimes warty or with fleshy masses	Skin-colored at first, sometimes reddened later	Vague	New lesions may appear near old ones
					Does not clear with corticosteroid therapy
Keratoacanthoma (a variant of squamous cell carcinoma)	Exposed areas, especially face and hands	Smooth dome, becoming volcano-shaped	Skin-colored or slightly reddened	Well-defined	Goes through aperiod of very rapid growth, often regresses
Eczema and atopic dermatitis (Figure 13)	Atopic dermatitis behind ears, on flexure areas	Reddened, slightly scaly, sometimes with vesicles	Dry at first, fissured, may weep	Indefinite	Common in atopic persons and those exposed to irritants
Contact dermatitis (Figure 14)	Wherever skin comes in contact with an irritant	Reddened, slightly scaly, sometimes with vesicles	Dry at first, fissured, may weep	Circumscribed	Dermatitis clears with corticosteroid therapy
Psoriasis (Figure 15)	Elbows, knees, scalp, sacral cleft, nails	Scaly with underlying reddened base	White dry scales, smooth pink or red wherescales are removed; may bleed	Well-demarcated; round, irregular or confluent	Often widespread, sometimes itchy; varies with season
Seborrheic dermatitis (Figure 16)	Scalp, forehead, nasolabial fold, midline trunk	Raised, with scales	Yellow or brown	Well-demarcated	Some lesions can be easily removed