Dermoscopy of other non-melanocytic lesions

Learning objectives
Introduction
Dermoscopy of haemangioma
Dermoscopy of haemorrhage
Dermoscopy of dermatofibroma
Dermoscopy of neurofibroma
Dermoscopy of Bowen's disease
Dermoscopy of actinic keratosis
Dermoscopy of lichenoid keratosis
Dermoscopy of porokeratosis
Dermoscopy of sebaceous hyperplasia
Dermoscopy of viral warts
Dermoscopy of epidermal naevus
Dermoscopy of nipple
Dermoscopy of cysts
Dermoscopy of clear cell acanthoma
Other uses for dermoscopy
Activity

Learning objectives

• Describe dermoscopic features of pigmented and non-pigmented non-melanocytic lesions

Introduction

Dermoscopy is useful to distinguish pigmented non-melanocytic lesions from benign and malignant melanocytic lesions. There are specific features that help to distinguish these.

Careful observation has resulted in the description of the dermoscopy of many non-pigmented lesions as well, which may be sometimes helpful in diagnosis for an itchy rash.

Dermoscopy of vascular lesions

The dermoscopic features of haemangiomas or angiomas are:

• Widespread red-blue lacunes
• Red-bluish-black homogeneous areas

Cutaneous lymphatic malformation (formerly called lymphangioma circumscriptum) has yellowish lacunes, sometimes tinged with blood.

Kaposi sarcoma under polarised microsocopy is characterised by multicoloured rainbow pattern in association with bluish-red colour, scaling and small brown globules. The rainbow pattern is occasionally seen in melanoma and other skin lesions.

Dermoscopy of haemangiomas

Cherry angioma	Cherry angioma	Cherry angioma	Cherry angioma
Cherry angioma	Angioma on lip	Venous lake on lip	Haemorrhagic lymphatic malformation

Dermoscopy of haemorrhage

Haemorrhage can be distinguished from pigmentation due to melanin by the purple colour. On plantar surfaces (e.g. talon noir) it may appear to have a parallel ridge pattern of discolouration with peripheral reddish-black globules. It may be helpful to shave off the surface keratin – sometimes biopsy is necessary to rule out melanoma.

Blood on dermoscopy

Haemorrhage within seborrhoeic keratosis	Thrombosed haemangioma	Senile purpura diffuse pinkness	Subungual haemorrhage
Talon noir (macro) black heel, due to trauma	Talon noir (dermoscopy) globules on ridges	Talon noir (dermoscopy) globules on ridges	Talon noir (dermoscopy) globules on ridges

Dermoscopy of dermatofibroma

The dermatofibroma (also known as histiocytoma) is usually easy to diagnose clinically because of a firm fibrous consistency and surface dimpling on compression. Typically, dermoscopy of a dermatofibroma shows a faint network or pseudonetwork surrounding a pale amorphous area. Sometimes the central white area has white lines and brown holes (negative network).

Haemosiderotic dermatofibroma (uncommon) is composed of numerous small vessels, extravasated erythrocytes and intra- and extracellular haemosiderin deposits. Dermoscopy reveals multicomponent pattern with a central bluish or reddish homogeneous area in combination with white or yellowish structures and a peripheral delicate pigment network.

Dermoscopy of dermatofibroma

Dimpling sign (dermatofibroma)

Dermoscopy of neurofibroma

The common type of solitary neurofibroma is often clinically misdiagnosed as dermal naevus or skin tag. They are soft to firm papules or nodules. The buttonhole sign is helpful: you can push the lesion through a defect in the dermis and it bounces back when pressure is removed.

Dermoscopy reveals a featureless nodule.

Dermoscopy of neurofibroma

Dermoscopy of Bowen's disease

Dermoscopy can be helpful for diagnosing pigmented Bowen's disease (squamous cell carcinoma in situ). Irregular so-called ‘glomerular vessels’ are characteristic. They may be associated with a scaly surface, small brown globules and/or homogeneous pigmentation.

Non-pigmented Bowen's disease can be difficult to diagnose by dermoscopy. Compared with basal cell carcinoma, there is more scaling and the vascular pattern is glomerular rather than arborising. Compared to psoriasis, the lesion is asymmetrical and the structure irregular.

Dermoscopy of Bowen's diseae: purple arrow shows glomerular vessels

Deeply pigmented lesion resembling melanoma

Dermoscopy of actinic keratoses

Actinic (solar) keratoses may be pigmented or non-pigmented. They have an erythematous pseudonetwork on facial skin, in which there are prominent hair follicles surrounded by a white halo. If the folllicle has a yellow central plaque they may look like a target. Pigmentation may be due to grey or brown dots and globules, or to a broken-up pseudonetwork, resembling lentigo maligna.

On non-facial sites, actinic keratoses present with uniform pink or tan-coloured background and prominent keratin (white or yellow scale).

Dermoscopy of solar keratoses

Pigmented solar keratosis with pseudonetwork		Non-pigmented solar keratoses

Dermoscopy of lichenoid keratosis

Lichenoid inflammation affecting a solar lentigo or seborrhoeic keratosis typically results in localised destruction of melanocytes and free melanin in the dermis or melanin within melanophages. These appear as granular areas of grey dots. Grey dots can also be typically seen within melanoma. However the lichenoid keratosis has no pigment network and there are usually amorphous areas with or without keratinous surface /or other features of seborrhoeic keratosis.

Dermoscopy of lichenoid keratosis: yellow arrows show grey dots

Dermoscopy of porokeratosis

Porokeratosis is distinguished by a cornoid lamella around the lesion. Sometimes there is prominent follicular plugging

Dermoscopy of porokeratosis

Porokeratosis of Mibelli

Disseminated superficial actinic porokeratosis

Follicular plugging

Dermoscopy of sebaceous hyperplasia

Sebaceous hyperplasia is distinguished by pale yellow lobules around a central follicular opening. Telangiectasia is common but tends to be uniform, in contrast to the irregular arborising vessels seen in basal cell carcinoma.

Dermoscopy of sebaceous hyperplasia

Dermoscopy of viral warts

Viral warts are keratinocytic lesions with a lobular structure (like frog spawn), sometimes with a central thrombosed capillary within each lobule. The normal dermatoglyphics are interrupted. Some have a papilliform structure.

In contrast, a corn has a translucent central core, and a callus is hyperkeratotic without other distinguishing features.

Dermoscopy of viral warts

Common wart

Common wart

Plane warts

Plantar wart

Dermoscopy of epidermal naevus

An epidermal naevus resembles a seborrhoeic keratosis or viral wart, with fissures, crypts and milia. However it is very uniform in appearance and appears within the first decade.

Dermoscopy of epidermal naevi

Dermoscopy of nipple

The areola and nipple are usually clinically obvious of course. However, an accessory nipple (present in 1 in 18 individuals) may resemble a compound naevus. Characteristically, the breast tissue has a delicate uniform peripheral pigment network.

Dermoscopy of the nipple

Accessory nipple (Dermoscopy not available)

Normal areola

Normal areola & naevus

Normal areola & naevus

Dermoscopy of cysts

Close inspection of a cyst will show the follicular opening.

Dermoscopy of cysts

Large epidermal cyst

Large epidermal cyst

Giant comedo

Xanthelasma (no opening)

Dermoscopy of clear cell acanthoma

The clear cell acanthoma is an unusual benign epidermal tumour with characteristic dermoscopic features. There are multiple pinpoint or dotted vessels arranged in line like a string of pearls.

Dermoscopy of clear cell acanthoma

Other uses for dermoscopy

The vascular pattern seen on dermoscopy can be used to diagnose red scaly plaques:

• Amelanotic melanoma: atypical and polymorphous vascularity
• Superficial basal cell carcinoma: arborising telangiectasia, ulceration
• Squamous cell carcinoma in situ: grouped glomerular vessels
• Psoriasis: uniform distribution of red dots on a light pink homogeneous background
• Lichen planus: white Wickham's striae, paucity of vessels

Red scaly plaques

Psoriasis (macro)

Psoriasis (dermoscopy) Vessels are tiny red dots; scale is in flakes

Lichen planus (macro)

Lichen planus (dermoscopy) Avascular, white scaly line

Other uses for dermoscopy include:

• To identify a scabies mite and/or its faeces within its burrow. The head is triangle shaped on its back, and anchor shaped on its front, like a jet-plane.
• To confirm the presence of nits gripping a hair shaft in pediculosis capitis (a filled egg case has a dark tip and is bullet shaped; an empty one is transparent, and shorter with a flat top).
• For cuticular capillaroscopy in suspected connective tissue disease.

Other uses for dermoscopy

Burrow: arrows point to scabies mites

Burrow: arrow points to scabies mite

Capillaroscopy: normal nail fold

Cutaneous lupus prominant loop capillaries

Activity

How does nail fold capillaroscopy distinguish lupus erythematosus from systemic sclerosis?

 

Page 9 of 15. Next topic: The first step algorithm. Back to: Dermoscopy course contents.