Skin Lesions

Description of a skin lesion

When describing a skin lesion, it is important to note the following features:

• Size
• Type
• Shape and symmetry
• Colour and pigmentation
• Surface features (smooth; rough)
• Distribution over the body (extensor surfaces; flexor surfaces)

Lesions may be further subdivided into primary and secondary lesions:

Primary lesion

 An area of tissue with impaired function due to damage by trauma or disease.

Secondary lesion

 A lesion arising as a consequence of any primary lesion.

1) Types of skin lesions

Lesions can be classified as primary or secondary lesions. Primary lesions can be classified into the following types:

• Macule
• Patch
• Papule
• Nodule
• Plaque 
• Vesicle
• Bulla
• Pustule
• Abscess

Secondary lesions can be classified into the following types:

• Scale
• Crust
• Ulcer
• Fissure
• Atrophy
• Lichenification

Flat lesions

Macule

A flat lesion, less than 0.5cm in diameter with an area of colour change. 

Conditions in which macules appear:

• Small pox
• Purpura
• Roseola

Patch

A lesion which is more than 0.5cm in diameter with an area of colour change. 

Examples of a patch:

• Measles
• Flat moles
• Freckles

Raised lesions

Papule

A palpable lesion which is less than 0.5cm in diameter.

Examples of papules:

• Actinic jeratosis
• Senile sebaceous hyperplasia
• Dermatofibroma

Nodule

 A papule with a diameter of more than 0.5cm.

Examples of nodules:

• Herpes simplex virus 
• Rheumatoid arthritis 

Plaque

 A papule with a diameter of more than 0.5cm. 

Examples of plaques:

• Psoriasis typically present with a plaque-like lesion

Fluid-filled lesions

Vesicles

 Fluid-filled lesions with a diameter less than 0.5cm.

Examples of vesicles:

• Impetigo
• Contact dermatitis
• Insect bites

Bulla

 A fluid-filled lesion with a diameter more than 0.5cm.

Examples of bullae:

• Bullous pemphigoid 
• Pemphigus 
• Dermatitis herpetiformis 
• Chronic bullous dermatosis 
• Cutaneous radiation syndrome
• Epidermolysis Bullosa

Pustule

 A fluid-filled vesicle containing neutrophils (ie pus).

Examples of causes of pustules-

• Acne vulgaris
• Rosacea
• Folliculitis

Abscess

A fluid-filled lesion containing neutrophils and is more than 0.5cm in diameter. Bacterial infections of skin such as Staphylococcus Aureus can cause abscesses on the skin. 

Secondary lesions

Scales

 Epidermal cells produced by abnormal keratinisation of the skin which have died and then been shed.

Crust

 A dried collection of serum and cellular exudates.

Ulcer

 A discontinuation of an epithelial lining extending into the epidermis/dermis.

Example of ulcers-

• Arterial ulcer- caused by ischaemia and are usually located on the lateral aspect of the ankle or distal ends of the digits of the lower limbs
• Venous ulcer- due to valvular insufficiency of the veins 
• Neuropathic ulcer- related to sensory loss in the lower limbs, most common in diabetes

Fissure

 A linear discontinuation of the epithelial lining with a sharply demarcated margin, which can extend in to the dermis.

Fissures may occur as a consequence of the primary lesions mentioned or may also occur in response to-

• Scratching
• Trauma
• Infection.

Atrophy

 A thinning in the epidermis/dermis which in turn leads to depression of the skin. 

Lichenification

Thickening of the epidermis which may be caused by scratching.

Examples of lichenification-

• Eczema
• Contact dermatitis.

2) Colour-

Examples of colour changes in lesions:

Red/purple

Erythema- redness due to increased blood flow to blood vessels (vasodilatation) in that area.

Purpura- red/purple discolouration due to extravasation of blood into the skin from a blood vessel.

Brown

Melanin- a pigment found in the skin which gives a brown discolouration.

Haemosiderin- the breakdown product of haemoglobin so can follow on from purpura and appears as a brown discolouration.

Yellow

Lipid deposition- xanthelasma (cholesterol deposits around the eyelids) and xanthomata (cholesterol deposits in the tendons) can occur in hyperlipidaemia disorders.

Bilirubin- yellow discolouration due to jaundice (which is defined as bilirubin >35µmol)

3) Describe the surface features

Normal- lesion lies below skin surface

Or-There may be evidence at the skin surface such as-

Break in epithelial surface- exudate, crust, ulcer or a fissure.

Change in the size of epidermis/dermis-lichenificationor epidermal/dermal atrophy.

Change in the stratum corneum (the outermost layer of the epithelium composed of dead cells)-

Hyperkeratinosis- thickening of the stratum corneum due to increased keratin deposition in these cells.

Scales

4) Define the area involving the lesion-

Is the border well or poorly defined?

Look at the centre of the lesion- is it continuous with the rest of the lesion or is it raised/depressed?

5) Desribe the shape of the lesion-

The shape of the area on the skin surface- is it round, oval or irregular?

Overall shape of the lesion- spherical, domed, pedunculated (lesion attached to skin by a narrow stalk), flat-topped.

6) Findings on palpation-

Consistency-

is it soft, firm, hard or indurated (can feel thickening within the lesion)?     

or the lesion could have the consistency of normal skin.

Conclusion-

When describing a skin lesion consider the six points covered-

1) type of lesion,

2) colour of lesion,

3) surface features,

4) area involved,

5) shape of lesion,

6) findings of palpation.

OSCE example-

Example OSCE station:

"Please describe the lesion on the right."

In order to describe the lesion follow the 6 steps detailed above-

1) Type-

• This is a primary lesion as it is a pathology in its own right rather than a consequence of an existing pathology, thus you can rule out secondary lesions such as scale, crust, ulcer etc.
• It is a non-raised lesion- thus you can rule out raised lesion types such as papule, nodule and plaque
• There is no fluid so you can rule out fluid-filled lesions such as pustule and abscess, vesicle and bulla
• Thus the remaining two are macule and patch depending on the size of lesion, if it is >0.5cm it is a patch and <0.5cm it is a macule

2) Colour- the lesion is dark, a potential cause of this colour could be the pigment melannin

3) Describe the surface features- this is a non-raised lesion which lies below the skin surface

4) Define the area involving the lesion- the lesion has a poorly defined border

5) Describe the shape of the lesion- the lesion has an irregular shape

6) Findings on palpation- is it hard vs. soft?

  firm vs. moveable?

Thus a summary of the description of this lesion could be something along the lines of:

"This is a dark, non-raised macular lesion with a poorly defined border and an irregular shape. Given the dark discolouration and the nature of the shape and the lesion's border, a possible cause could be melanoma."