Seborrhoeic keratoses and Variants

Seborrhoeic keratoses are a form of acanthoma or thickening with hyperplasia of normal keratinocytes in the epidermis. The rete ridges are usually flattened out or bulbous. The cells are not atypical and there are no mitoses.

The variants architecturally of Seb ks include acanthotic, hyperkeratotic, clonal and reticulated. These can also be irritated or inflammed. Irritated seb ks show structures called squamous eddies while inflammed show a lymphocytic infiltrate around them. A melanoacanthoma is a deeply pigmented vaiant of a seb k made up of keratinocytes and dendritic melanocytes.

The stratum corneum above a seb k is usually a loose lamellar type except if irritated or inflammed when you can see parakeratotic features. The stratum corneum over a melanoacanthoma is always parakeratotic.

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Seborrhoeic keratosis

Inflammed Seborrhoeic Keratosis

Irritated Seborrhoeic Keratosis

Reticulated Seborrhoeic Keratosis

Clonal Seborrhoeic Keratosis

Melanoacanthoma

Seborrhoeic Keratosis with SCC arising within