DIFFERENTIAL DIAGNOSIS OF PIGMENTED LESIONS: INTRODUCTION
Perhaps the most difficult and concerning aspects of the dermatologic physical exam rest on the provider's ability to evaluate pigmented lesions. Such lesions represent a large portion of visits due to patients' concerns regarding rapid growth, change in shape, symptoms such as pruritus, or recent bleeding. The following figures highlight the most reliable features in evaluating pigmented lesions, though overlap does exist between characteristic features. When clinical doubt exists, skin biopsy for histopathologic evaluation or referral to a dermatologist is recommended.
Common Pigmented Lesions Encountered in Primary Care Medicine.
Melanocytic nevus These lesions show even pattern of pigmentation, with regular borders and symmetry. This papule is less than 0.5 cm in diameter.
Dysplastic nevus This lesion has both macular and papular components with uneven pigmentation but fairly regular borders and symmetry. There are no areas of "regression" (steel-gray discoloration that is residual from the body's attempt to have the lesion recede).
Melanoma This brown and black papule has uneven borders, is asymmetric, and has color variation including red and blue hues. The lesion is larger than 0.6 cm and arose quickly with uneven relief in its surface. Note that there is pigment spread suggesting lateral spread or "radial growth phase."
Seborrheic keratosis These lesions usually occur in multiples. A solitary verrucous papule may present diagnostic difficulty and biopsy is often indicated. A verrucous surface with "stuck on" appearance, horn cysts and lack of dermal infiltration, suggests a diagnosis of seborrheic keratosis.
Angiokeratoma This papule has a pebbled surface and is noncompressible (unlike a venous lake). On close examination, thrombosed vascular spaces can be seen (see arrow).
Pigmented basal cell carcinoma Confusion can arise with a cutaneous melanoma. Translucency in the lesion and a pattern of surrounding telangiectasia are more commonly seen in pigmented basal cell carcinoma.
Dermatofibroma Dome-shaped papule with regular and even pigmentation; when pressed from each side, a dimple sign can be elicited.
Pyogenic granuloma These acute papules and nodules occur soon after trauma, tend to be beefy-red and in the palms and soles have a collar of thickened stratum corneum at the base.