Seborrhoeic keratosis (syn. seborrhoeic wart, basal cell papilloma)

LAST UPDATED: Jun 05, 2026

Patient Information Leaflet
Link: Seborrhoeic keratoses

https://www.pcds.org.uk/patient-info-leaflets/seborrhoeic-keratoses

Introduction

A seborrhoeic keratosis (sebK) is a benign (harmless) overgrowth of epidermal keratinocytes of unknown aetiology that is prevalent in middle-aged and older individuals.

This chapter is set out as follows:

History

  • Age of presentation - most commonly present from the fourth decade onwards; younger adults can be affected
     
  • Symptoms
    • Can be asymptomatic or itch
    • May grow
    • Non-tender unless traumatised
    • Part / all of the lesion can come away with minimal trauma

Clinical findings

Clinical examination

  • Distribution
    • The trunk and face are commonly affected; can arise on almost any body site
    • It is not uncommon to find multiple lesions; some patients have very large numbers (especially if there is a family history)
       
  • Colour - yellow/brown to black, thinner lesions are paler, and traumatised lesions appear inflamed
     
  • The most common presentation is that of a thickened lesion with the following characteristics:
    • Scaly or 'greasy' in appearance, sometimes with an irregular verrucous surface
    • ‘Stuck-on’ - the lesion sits on top of normal looking skin and gives the impression that it can be easily picked off
    • Most are 1-3 cm in diameter; some are very large
    • Can grow on top of solar lentigos 
       
  • Thinner lesions most commonly arise on areas of thinner skin (eg lower legs and forearms) and are more subtle, generally lighter in colour 
     
  • A verrucous keratosis - is where a viral wart has started to grow within a seborrhoeic keratosis. These changes are apparent both clinically and histologically
     
  • The Leser-Trélat sign - this is characterised by the abrupt appearance of multiple seborrhoeic keratoses that rapidly increase in their size and number. There is debate as to whether or not this is a paraneoplastic phenomenon (associated with adenocarcinoma of the stomach or colon) due to the high prevalence of multiple seborrhoeic keratoses in elderly populations, however, should lesions erupt in the presence of weight loss, GI symptoms, malignant acanthosis nigricans or other 'red flags' then patients should be referred urgently for further investigations

Dermoscopic features (hover over terminologies for description)

Seborrhoeic keratoses take on various appearances. The four most common patterns are:

  1. Acanthotic lesions have a thickened epidermis with comedo-like openings (clods) and milia-like cysts. The comedo-like openings tend to be less regular in terms of shape and distribution compared to globules seen in melanocytic lesions, they can also appear more grainy as opposed to smooth. While milia-like cysts can appear in other conditions, multiple cysts (more than three) strongly suggest a benign non-melanocytic lesion, most commonly a seborrheic keratosis. Bloods vessels should be relatively uniform looped structures (for more information on vessels refer to the chapter Vessel patterns in dermoscopy)
     
  2. Multiple fissures and ridges, sometimes with a cerebriform pattern (looking like the surface of the brain). Before lesions thicken the fissures and ridges have not yet developed and so appear as pigment bands (broader than lines, of variable length and width, are linear irregular or curved, and can be intertwined. Commonly yellow or brown). Alternatively, in very thin lesions some have small keratin scales that can build up in to a layered appearance 
     
  3. Grouped skin-coloured clods with a central blood vessel - this pattern is mainly seen in pale lesions and gives a frogspawn-like appearance. Sometimes grouped clods are separated by fissures
     
  4. Multiple small, brown, grouped, monomorphic (of the same or similar appearance) clods or circles - seen in some thinner lesions on the trunk and limbs. This is sometimes referred to as the 'clonal' pattern. Circles can also be found in dermatofibroma (at the periphery) and melanocytic lesions. The circles of seborrhoeic keratoses tend to be larger than those seen in melanocytic lesions

Dermoscopy is good for screening out many seborrhoeic keratoses; where doubt remains lesions should be referred for teledermoscopy or on an Urgent  Skin Cancer Pathway.  

Clinical Images

Please refer to notes on image rights at bottom of the page with regards to individual image ownership.

Seborrhoeic keratosis (sebK)Copied with kind…
1
Dermoscopic appearance of previous figureMultiple…
2
Large seborrhoeic keratosis on the trunkNote…
3
Multiple seborrhoeic keratosesCopied with kind…
4
Seborrhoeic keratosis growing on top of a solar…
5
Seborrhoeic keratosis on the trunkCopied…
6
Seborrhoeic keratosis on the right shoulderCopied…
7
A thin seborrhoeic keratosisLesions that are…
8
Dermoscopic appearance of the previous figureA…
9
Seborrhoeic keratosis - a 'stuck-on'…
10
Dermoscopy of previous figureSmall keratin scales…
11
Seborrhoeic keratosisMultiple clues -…
12
Thin seborrhoeic keratosisCopied with kind…
13
Dermoscopic appearance of previous figureMany…
14
Seborrhoeic keratosis on the backCopied with kind…
15
Dermoscopic appearance of previous…
16
Seborrhoeic keratosisCopied with kind permission…
17
Dermoscopic appearance of previous figure…
18
Seborrhoeic keratosisCopied with kind permission…
19
Dermoscopic appearance of previous figureThe…
20
Seborrhoeic keratosis - skin of colourCopied with…
21
Dermoscopic appearance of previous figureFissures
22
Seborrhoeic keratoses
23
Dermoscopic appearance of previous figure
24
Seborrhoeic keratosisCopied with kind permission…
25
Dermoscopic appearance of previous…
26
Seborrhoeic keratosis Multiple fissures…
27
Seborrhoeic keratosis right pre-auricularCopied…
28
Dermoscopic appearance of previous figureMultiple…
29
Seborrhoeic keratosisCopied with kind permission…
30
Dermoscopic appearance of previous figureCopied…
31
Seborrhoeic keratosis - irritated  If you…
32
Dermoscopic appearance of previous figure
33
A verrucous keratosisThe lesion on the left is a…
34
A verrucous keratosisFeatures of both a…
35
Dermoscopic image of a verrucous keratosisShowing…
36
A hyperkeratotic seborrhoeic keratosisA number of…
37
An ugly duckling? At first glance this…
38
Dermoscopic appearance of previous figure A…
39
Seborrhoeic keratoses on the…
40
Dermoscopic appearance of previous…
41
Seborrhoeic keratosis left pre-auricular…
42
Dermoscopic appearance of previous…
43
Close-up of a seborrhoeic keratosisNote the…
44
Dermoscopic appearance of previous…
45
Seborrhoeic keratosisThe lesion had a very…
46
Dermoscopic appearance of previous figure…
47
Many comedo-like openings in a dark seborrhoeic…
48
Seborrhoeic keratosis - many comedo-like…
49
Seborrhoeic keratosis - skin of colourCopied with…
50
Dermoscopic appearance of previous figureFissures…
51
Seborrhoeic keratoses in skin of colourCopied…
52
Dermoscopic appearance of the larger lesion in…
53
Dermoscopic appearance of the smaller…
54
Seborrhoeic keratosis in skin of colour
55
Dermoscopic appearance of previous figure Red…
56
Seborrhoeic keratosisCopied with kind permission…
57
Dermoscopic appearance of previous…
58
Thin seborrhoeic keratosis on the shinThe lesion…
59
Dermoscopic appearance of previous figureLarge…
60
Seborrhoeic keratosisThe differential diagnosis…
61
Dermoscopic appearance of previous…
62
An ugly duckling Seborrhoeic keratoses can…
63
Dermoscopy to the rescue - same lesion as…
64
Seborrhoeic keratosis with looped/hairpin…
65
A very pale seborrhoeic keratosis - dermoscopy…
66
Dermoscopic appearance of previous figureA single…
67
Irritated seborrhoeic keratosisCopied with kind…
68
Dermoscopic appearance of previous figureEvidence…
69
Another irritated seborrhoeic…
70
Seborrhoeic keratosisCopied with kind permission…
71
Dermoscopic appearance of previous figure -…
72
Seborrhoeic keratosis on the right templeCopied…
73
Dermoscopic appearance of previous…
74
Dermoscopic vascular patterns in seborrhoeic…
75
Seborrhoeic keratosis - frogspawn patternCopied…
76
A thin seborrhoeic keratosis - top of…
77
Seborrhoeic keratosis - thinCopied with kind…
78
Dermoscopic image of previous figureMultiple…
79
Seborrhoeic keratosisCopied with kind permission…
80
Dermoscopic image of previous figureMultiple…
81
Seborrhoeic keratosisMultiple small, brown,…
82
Seborrhoeic keratosis
83
Dermoscopic image of previous figureMultiple…
84
Seborrhoeic keratosisWhen circles are seen in…
85
Seborrhoeic keratosisMultiple small, brown,…
86
A seborrhoeic keratosisYellow/brown with large…
87
Circles in different lesionsAs with any skin…
88
Collision tumour A collision tumour is…
89
Dermoscopic appearance of previous figure…
90
Collision tumour - dermoscopic…
91
Collision tumourSeborrhoeic keratosis (purple…
92
Dermoscopic appearance of previous…
93
Seborrhoeic keratosis on the right…
94
Seborrhoeic keratosis - same patient as…
95
Dermoscopic appearance of same lesion The…
96
Blue and black - sebk's (upper two images),…
97
An important lesson - dermoscopy must always be…
98
Clinical appearance of the previous…
99

Management

  • Most seborrhoeic keratoses do not require treatment but for those that do the majority can be treated by liquid nitrogen (for more information refer to the chapter Cryosurgery). Very thick lesions are best removed by curettage and cautery - all samples should be sent for histology
     
  • If there is any uncertainty about the diagnosis the patient should be referred urgently for teledermoscopy or to Secondary Care (Urgent Skin Cancer pathway)

Disclaimer - the author PCDS cannot accept responsibility for any misleading or incorrect statements, and the management of individual patients remains the direct responsibility of the individual doctor. We do however hope that visitors to this site can contact us regarding comments that are considered misleading or incorrect so that we can continue to improve the site.

Image Rights - The PCDS would like to thank Dermatoweb, DermQuest (Galderma), and others who have contributed images. All named individuals and organisations maintain copyright for the relevant images.

Download the Patient Information Leaflet PDF

Download

Quick Links

ALL
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z

Medical Images

It is important for the PCDS to build its own image bank, as such we welcome original images from our readers, especially in skin of colour:

The following pharmaceutical companies have had no involvement in the content of this website or in our conference programmes

Almirall
Galderma
Glenmark
Johnson & Johnson
La Roche-Posay
LEO Pharma
Pierre Fabre
Schuco

View all sponsors