What are pigmented skin lesions?
Pigmented skin lesions refer to lesions that are brown, black or blue in colour, or may be confused with brown or black lesions (for example, vascular lesions, which sometimes look black with the naked eye but under dermatoscopy appear red, purple or blue).
What is the pigment?
The colour of pigmented skin lesions is due to:
- Melanin
- Blood
- Exogenous pigment (for example, tattoo)
What are the possible diagnoses for pigmented skin lesions?
Pigmented skin lesions are most often melanocytic. However, non-melanocytic lesions can also be pigmented, particularly in dark-skinned individuals. Non-melanocytic lesions are keratinocytic, vascular, or reactive.
Melanocytic lesions
- Benign melanocytic naevus (moles of various kinds including blue naevus)
- Melanoma
Pigmented melanocytic lesions
Keratinocytic lesions
- Seborrhoeic keratosis
- Lentigo (freckles of various kinds including solar lentigo)
- Epidermal naevus including Becker naevus
- Pigmented basal cell carcinoma
- Pigmented actinic keratosis and intraepidermal carcinoma (also called squamous cell carcinoma in situ, Bowen disease)
- Pigmented squamous intraepithelial lesions of vulva, penis, anus
- Pigmented invasive squamous cell carcinoma
Pigmented keratinocytic lesions
Vascular lesions
- Trauma eg splinter haemorrhage in nail
- Purpura from bruise, capillaritis, vasculitis
- Cherry angioma
- Angiokeratoma
- Angiosarcoma
- Kaposi sarcoma
Dark-coloured vascular lesions
Reactive pigmentation
- Dermatofibroma
- Dermatofibrosarcoma protuberans
- Postinflammatory pigmentation
- Other pigmented skin condition such as lichen planus
Reactive pigmented lesions
Many other lesions and skin conditions are occasionally mistaken for a melanocytic or keratinocytic pigmented skin lesion.