Seborrheic Keratosis (SK) (Figure 5.1A–C) - Common benign growth often seen after third decade of life
- Typically light brown to yellow to dark brown papule or plaque with waxy or verrucous appearance and “stuck on” appearance
- Histology: hyperkeratosis, papillomatosis, acanthosis of epidermis, horn pseudocysts, and often increased melanin in basal layer or throughout entire epidermis
- At least five histological variants:
- Acanthotic SK: most frequently seen histologic type; smooth domeshaped papule with slight hyperkeratosis/papillomatosis but significant acanthosis and many invaginated horn pseudocysts, increased amount of melanin within keratinocytes
- Hyperkeratotic SK: exophytic lesion with significant hyperkeratosis and papillomatosis, only mild acanthosis, fewer horn pseudocysts
- Reticulated (adenoid) SK: interlacing thin strands of basaloid cells and horn pseudocysts
- Clonal SK: intraepidermal well-defined nests of basaloid cells with uniform appearance
- Irritated SK: squamous eddies (whorls of eosinophilic keratinocytes) within epidermis, ± scattered necrotic keratinocytes, lymphoid infiltrate (lichenoid, perivascular or diffuse)
- Pigmented SK (melanoacanthoma): acanthotic, heavily pigmented SK
- Treatment: reassurance, cryotherapy, curettage, shave removal, laser treatment
| | | | | | Sign of Leser-Trelat: sudden eruption of SKs typically on trunk and associated with underlying adenocarcinoma (i.e., stomach, colon, etc.) | | | | | |
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| | Figure 5.1
A: Seborrheic keratosis
B: Seborrheic keratosis
C: Multiple SKs |
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