Dermoscopy

Dermoscopy of seborrhoeic keratosis CME

Created 2008.

Learning objectives

  • Describe dermoscopic features of seborrhoeic keratosis

Introduction

Dermoscopy is useful to distinguish pigmented non-melanocytic lesions from benign and malignant melanocytic lesions. There are specific features that help to distinguish seborrhoeic keratosis from basal cell carcinoma and melanoma. However, the distinction is not always possible and it may be necessary to excise some clinically atypical but histologically benign lesions.

The ‘wobble sign’ may be useful to distinguish a papillomatous melanocytic naevus from a stable seborrhoeic keratosis.

Dermoscopic features of seborrhoeic keratosis

Seborrhoeic keratoses typically reveal dermoscopic features that are fairly specific for the diagnosis. However, on occasions, melanocytic lesions, especially dermal naevi, congenital naevi, Spitz naevi and nodular melanoma, may have similar features and can be just as difficult to distinguish from seborrhoeic keratoses by dermoscopy as clinically.

Seborrhoeic keratoses can have an irregular structure and multiple colours (skin coloured, pink, grey, yellow, tan, dark brown, black, bluish).

Typical dermoscopic features include:

  • Milia-like cysts – there are two types:
    • Tiny white starry
    • Larger yellowish cloudy
  • Irregular crypts
  • Fissures/ridges
  • Blue-grey globules
  • Light brown fingerprint-like parallel structures
  • ‘Fat fingers’ (the gyri of a cerebriform surface)

There may also be a faint network or pseudonetwork. Blood vessels can be prominent in some seborrhoeic keratoses, tending to arise as tiny hairpin shaped capillaries surrounded by a halo within a lobule.

Dermoscopy of seborrhoeic keratoses

Identification of seborrhoeic keratoses by Chaos and Clues method

Seborrhoeic keratoses demonstrate "chaos" by modified pattern analysis, ie, they often have asymmetry of colour and structure on dermatoscopy — like pigmented skin cancers. Clinical clues to seborrhoeic keratoses are:

  • Multiple grouped similar lesions
  • Stuck-on lesion
  • Waxy or scaly surface

Dermatoscopic clues to seborrhoeic keratoses by modified pattern analysis are:

  • Multiple orange clods
  • Multiple white clods
  • Thick curved lines
  • Sharply demarcated border over total periphery

If features are equivocal, excise the lesion. Partial biopsy may be acceptable if low-risk lesions, providing full excision is arranged should the atypical lesion prove to be melanocytic.

Activity

Evaluate 20 pigmented seborrhoeic keratoses by dermoscopy. What proportion contain each of the following features:

  • Pigment network
  • Milia-like cysts
  • Irregular crypts
  • Fissures
  • Multiple colours (3 or more)

 

Acknowledgements

Online continuing medical education designed for health professionals and students.

Learning objectives will be listed for each topic.

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Acknowledgements  

Developed in collaboration with the University of Auckland Goodfellow Unit in 2007.

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2008.  

Images have been sourced from the following:

Course contents

  

 goodfellow unit logo

 

Related Information

References

  • Sahin MT, Ozturkcan S, Ermertcan AT, Gunes AT. A comparison of dermoscopic features among lentigo senilis/initial seborrheic keratosis, seborrheic keratosis, lentigo maligna and lentigo maligna melanoma on the face. J Dermatol. 2004 Nov;31(11):884-9. Medline.
  • Braun RP, Rabinovitz HS, Krischer J, Kreusch J, Oliviero M, Naldi L, Kopf AW, Saurat JH. Dermoscopy of pigmented seborrheic keratosis: a morphological study. Arch Dermatol. 2002 Dec;138(12):1556-60. Medline.
  • Chaos and Clues. An Algorithm for the Diagnosis of Malignancy (any type) in Pigmented Skin Lesions by Dermatoscopy. Rosendahl C, Cameron A, Tschandl P, Bulinska A, Gourhant JY, Kittler H. PDF file from cliffrosendahl(at sign)bigpond.com

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