What causes seborrheic keratosis (SK)?

Updated: Jan 30, 2020
  • Author: Ginard I Henry, MD; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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The exact etiology of seborrheic keratosis is unknown. The lesions exist in varying patterns. Generally, the lesion is exophytic with a base level flat with the epidermis. An increased number of basal cells are typically observed. These form cords or sheets of cells with cysts of keratin (horn cysts). When the cysts communicate with the surface, they are visible as keratin plug-filled pits. This assists in the differential diagnosis when discriminating seborrheic keratosis from melanomas and nevi. All seborrheic keratoses have varying degrees of acanthosis, papillomatosis, and hyperkeratosis. Hyperpigmentation of the basal cells may occur with any type and may further confound the diagnosis.

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