Actinic keratoses

Actinic, or solar, keratoses (AK) is a common premalignant skin lesion that develops as a consequence of chronic sun exposure

Features

• small, crusty or scaly, lesions
• may be pink, red, brown or the same colour as the skin
• typically on sun-exposed areas e.g. temples of head
• multiple lesions may be present

Multiple actinic keratoses - hyperkeratotic papules on a background of sun-damaged skin

Key Histological Features

• Epidermal Atypia/Dysplasia: Dysplastic, crowded, and pleomorphic keratinocytes in the basal layer with nuclear hyperchromasia and increased mitosis.

• Keratinization Patterns:

  • Parakeratosis: Retained nuclei in the stratum corneum.
  • Hyperkeratosis: Thickening of the stratum corneum.
  • Thinning of the granular layer: Often present, particularly in atrophic variants.

• Dermal Changes: Solar elastosis (blue-gray elastic fibers) is a hallmark of chronic sun damage.

• Inflammation: A dermal lymphocytic infiltrate is typically present.

  Medscape

Grading (Röwert-Huber System)

• AK I (Mild): Atypia confined to the lower third of the epidermis.

• AK II (Moderate): Atypia extending to the lower two-thirds of the epidermis.

• AK III (Severe): Full-thickness epidermal atypia.

  PubMed Central (PMC) (.gov)

Variants

• Hypertrophic: Prominent irregular acanthosis and hyperkeratosis.