FFinalistSouthampton · 2027
Dermatology
AKT · Dermatology/Benign lesions

Seborrhoeic keratosis

Benign proliferation of epidermal keratinocytes

Overview

A very common benign warty plaque of older adults with a characteristic "stuck-on" appearance, as if it could be flicked off. Sharply demarcated with a greasy/verrucous surface and horn cysts. The job is to distinguish it confidently from melanoma and pigmented BCC.

Recognise

  • Well-demarcated, "stuck-on", waxy/verrucous plaque, tan to dark brown, on the trunk/face of older adults
  • Surface horn cysts (keratin plugs) seen with the naked eye or dermoscopy; greasy feel
  • Multiple lesions are typical; benign and stable

Red flags

  • The sudden eruption of MANY seborrhoeic keratoses (sign of Leser-Trélat) can be a paraneoplastic marker of internal (often GI) malignancy; a changing/irritated lesion mimicking melanoma → biopsy

Differentials & how to tell them apart

Malignant melanomaasymmetric, changing, irregular pigment network — seborrhoeic keratosis is "stuck-on" with horn cysts and stable
Pigmented BCCpearly with telangiectasia
Melanocytic naevussmooth mole without the warty stuck-on surface
Viral wartHPV, often hands, no horn cysts/greasy surface

Clinical image

We can't host this one — the image is DermNet's and their licence doesn't cover us republishing it. Their page for it is free to view.

Seborrhoeic keratosis — clinical imagesDermNet

Investigations

Clinical/dermoscopy (horn cysts, "brain-like" surface). Biopsy if it cannot be confidently distinguished from melanoma.

Management

Reassurance; cryotherapy/curettage only for symptoms or cosmesis

  1. 1Reassure — the stuck-on appearance with horn cysts is a benign seborrhoeic keratosis.Gate: A sudden crop of MANY seborrhoeic keratoses (sign of Leser-Trélat) can herald an internal malignancy → consider investigation; and biopsy any single lesion that cannot be confidently separated from melanoma
  2. 2Symptomatic/irritated or cosmetically unwanted → cryotherapy, curettage or shave excision (send for histology if any diagnostic doubt).
Reassurance / no treatment — benign
Cryotherapy / curettage / shave — for irritation or cosmesis (with histology if any doubt)

Key points

"Stuck-on" + horn cysts = benign. The two traps are mistaking a pigmented one for melanoma, and missing the Leser-Trélat paraneoplastic sign.

Monitor & prognosis

Stability; review irritated/changing lesions.

Benign.

Source: NICE CKS; DermNet