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Seborrheic Keratosis 

Author: Dr Amy Prideaux 

Chief Editor: Dr Daniel Keith

Macroscopic Appearance

Also known as basal cell papillomas, they are very common presentation to primary care!

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Macroscopically these often have a 'stuck on' appearance. They are benign, age related spots of no consequence to general health. Despite this they a significant cause of patient anxiety.

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Multiple Seborrheic keratosis on the back of a patient with Fitzpatrick Skin Type 2. As you can see, there can be a wide variety of pigment variation within and between lesions, which can cause a lot of concern for patients and clinicians alike.

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Multiple Seborrheic keratosis on the back of a patient with Fitzpatrick Skin Type 6. As you can see the pigment variation is present, but much less pronounced than in the adjacent image displaying Type 2 Skin. The apperance of the lesions is otherwise extremely similar.

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Macroscopic example of a Seborrheic keratosis in Fitzpatrick Skin Type 2.

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Macroscopic example of one large and a few smaller Seborrheic Keratosis in Fitzpatrick Skin Type 6.

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Macroscopic example of a large Seborrheic Keratosis in Fitzpatrick Skin Type 2 (zoomed in on the largest lesion on the back of the patient above on the left).

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A collection of seborrheic keratosis on the cheek of a patient with Fitzpatrick skin type 2. 

Dermoscopic Appearance

Milia like Cysts and Comedo Like Openings

 

Dermoscopic appearance in Fitzpatrick Skin Type 2

 

Milia like cysts:

  • bright yellow or white circles

  • represent pearls of keratin under the surface

 

NB Milia like cysts will show up more clearly in polarised dermoscopy!

 

Comedo like openings:

  • small holes or pits in the surface

  • sometimes plugged with keratin pearls

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In this image you can see the dermoscopic appearance in Fitzpatrick Skin Type 6.

 

As you can see the features are exactly the same as in the above example of Type 2 skin:

 

  • Milia like cysts

  • Comedo like openings

 

The only difference between this example, and example 1 above, is the addition of more pigment throughout.

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Another nice example of milia like cysts and comedo like openings, in Fitzpatrick Skin Type 6.

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A further dermoscopic example in Fitzpatrick Skin Type 2 showing multiple comedo-like openings and milia like cysts.

Papillomatous features

 

These features are seen in any papillomatous lesions including seborrheic keratosis and viral papilloma.

 

They may consist of:

  • Frog spawn sign (bubbly appearance)

  • Fat fingers (these are warty like projections and can occur when the frog spawn sign elongates into sausage or finger like projections)

 

Below are two examples (annotated and unannotated) in Fitzpatrick Skin Type 2.

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Comedo like openings + Milia like cysts + Papillomatous Features

 

Again in Fitzpatrick Skin Type 2, there are some small comedo like openings visible in the darker area on the left, along with a few small milia like cysts.

 

This transitions into papillomatous features in the central and right sided paler area. In this case you can mainly see the frog spawn sign with it's bubbly appearance.

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Cerebriform pattern

 

This is another pattern you may come across in a seborrheic keratosis. It resembles the appearance of a brain and you may be more likely to come across this pattern in crypts and folds in the surface of the lesion.

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Sulci in this example are highlighted by make up which couldn't be cleaned out fully.

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This is an annotated example in Fitzpatrick Skin Type 2.

Some further examples of seborrheic keratosis directly comparing the macorscopic to the dermoscopic appearance in different skin types:

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Macroscopic appearance in this example of Fitzpatrick Skin Type 6:

  • Pigmented, stuck on lesion which stands out from the surrounding skin and is well defined

  • Warty, subtle pigment variation

  • In comparison to Skin Types 1 and 2, the pigment is deeper with less colour variation.

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 6:

  • lots of bright milia like cysts

  • crypts and comedo like openings can also be seen

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Macroscopic appearance in this example of Fitzpatrick Skin Type 1:

  • Pigmented lesion which clearly stands out

  • Multiple colours - shades of brown, red, black

  • Asymmetrical

  • Well defined borders and 1cm across

  • Appears stuck on

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 1:

  • lots of bright milia like cysts

  • some small comedo like openings

  • papillomatous features with frogs spawn at the top

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Macroscopic appearance in this example of Fitzpatrick Skin Type 1:

  • warty

  • large

  • asymmetrical

  • multicoloured - light and dark brown with some black spots

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 1:

  • papillomatous features - fat fingers and crypts

  • the dark capillaries are thrombosed capillaries, which can also be seen in papillomatous lesions

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Macroscopic appearance in this example of Fitzpatrick Skin Type 2:

  • large, warty lesion on the scalp

  • noticed after shaving head

  • 2cm irregular lesion

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 2:

  • multiple finger like, warty projections frogs spawn bubbly appearance

  • some thrombosed capillary loops in the lower aspect of the image

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Macroscopic appearance in this example of Fitzpatrick Skin Type 2:

  • very dark, ugly duckling type lesion which was itchy

  • warty stuck on appearance

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 2:

  • milia like cysts

  • crypts and comedo like openings

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Macroscopic appearance in this example of Fitzpatrick Skin Type 2:

  • 6mm warty lesion which appears to have been bleeding

  • signs of picking some sensory change

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Dermoscopic appearance in this example of Fitzpatrick Skin Type 2:

  • papillomatous/cerebriform features

  • trauma to the top edge where it has been scratched or picked (not unusual to see)

  • grey speckling superior to the trauma which may be regressing lichenoid keratosis (see below)

Regressing lichenoid keratosis

 

  • Where a keratosis (usually seborrheic keratosis or benign solar lentigo) undergo spontaneous regression

  • May be accompanied by inflammation or preceding trauma

  • It is the shadow left behind after a lesion suddenly becomes inflammed, itchy and swollen, before falling off and can occur at any point in this cycle

  • Dermoscopically you see annular granular dusty grey pigmentation.

  • The dusty appearance is typical, and the patient can be reassured as this is benign

  • The shadowy, left over debris will slowly fade over a number of months

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Below are macroscopic and dermoscopic examples of this phenomenon

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Referred as an itchy lesion on the face

 

Since referral the lesion had fallen off or had been shaved off during normal shaving

 

A grey shadow on the cheek can just about be made out

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Under dermoscopy you can see the granular, grey, dusty pigmentation.

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Irritating longstanding wart on the arm which suddenly started itching

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Under dermoscopy there are some comedo like openings, but at the periphery you can see the granular grey pigment.

 

It is likely that this seborrheic keratosis may spontaneously involute over the next few weeks, leaving the grey dust behind.

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A macroscopic example. As you can appreciate the upper section of the lesion resembles a grey shadow, in keeping with regressing lichenoid keratosis.

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You can see on dermoscopy at 6 o'clock the residual seborrheic keratosis, and above this is the granular grey dust of regressing lichenoid keratosis.

The following images show further examples of regressing lichenoid keratosis, and are specifically credited to Dr. Catherine Matthews, GP.

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Macroscopic image of a seborrheic keratosis in it's normal state

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After traumatisation

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Dermoscopy of the grey granular dusty debris

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