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For the clinician a clear knowledge of the most common benign tumors and important. Identifying a lesion that falls outside of the spectrum of common benign tumors and requires further evaluation or referral is critical. This fundamental insight will help alleviate the concern of a patient who presents with an otherwise benign lesion. It will also allow the clinician to first screen and differentiate common lesions that may have simple treatments, or no required treatment, from those lesions that are of more concern.


Clinical Presentation

History and Physical Examination

Seborrheic keratoses are present in approximately 50% of adult patients. Many patients present with a history of a changing pigmented "mole" and a concern about melanoma. Patients may complain of pruritus or irritation from clothing. A classic seborrheic keratosis has a predilection for the trunk and presents as a well-defined hyperpigmented papule or plaque with a waxy hyperkeratotic surface, ranging in size from a few millimeters to several centimeters in diameter (Figure 16-1). They are often oval in shape with their long axis following the natural tension lines of the skin. The astute clinician can quickly recognize these lesions and avert the need for a biopsy, but occasionally even with the most trained eye a biopsy is indicated. Variants include the macular seborrheic keratosis of the face and scalp that present as a slightly raised velvety plaque or pigmented macule on the head and neck. These lesions are often misdiagnosed as a lentigo with concern for lentigo maligna melanoma. A facial variant is dermatosis papularis nigra which presents primarily in African Americans with small dark papules (Figure 16-2). Stucco keratosis is another variant and presents as smaller scattered lightly pigmented or white keratotic papules on the distal lower extremities (Figure 16-3).

Figure 16-1.

Seborrheic keratosis. Tan to brown plaques with a waxy hyperkeratotic surface.

Figure 16-2.

Dermatosis papularis nigra. Variant of seborrheic keratosis seen in African Americans.

Figure 16-3.

Stucco keratosis. Variant of seborrheic keratosis seen on legs and feet. Presents with small white hyperkeratotic papules.

Laboratory Findings

Histopathology shows that all variants of seborrheic keratosis are limited to thickening of the epidermis with trapping of keratin in elongated tracks called horn pseudocyts. These can be seen under dermoscopy or by careful observation with the unaided eye.

Differential Diagnosis

  • Lentigo: Macule with even hyperpigmentation and a smooth scalloped border, most commonly on sun-exposed areas of face and hands.

  • Nevus: Tan to black macules or papules; surface is ...

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