Introduction
The skin is complex with an array of functions. It is the body’s largest organ, undertaking the major physi- ological functions of regulation of the body tempera- ture, protection, sensation, excretion, immunity and synthesis of Vitamin D. Many skin disorders can be diagnosed through direct observation and palpation but others may require referral to a dermatology spe- cialist or expert. Patients can present with a wide range of skin anomalies. Some of these can prove to be relatively normal, whilst in the extreme, others can be life threatening, making accurate and timely assessment and diagnosis crucial. Investigations are often neces- sary and may involve a microscopic or histo-patho- logical examination of the area of skin involved, or radiological imaging.
Skin biopsy is a procedure where a portion of the skin is removed. This skin sample is examined by the histopathologist, who may provide insight to the likely diagnosis or aetiology of a skin disorder. This infor- mation can be obtained by using light-microscopic examination of paraffin-embedded tissue, electron/ ultrastructural microscopic examination, immunofluo- rescence studies and immunohistochemistry. Micro- biological studies, tissue culture and molecular biological methods such as in situ hybridization and polymerase chain reaction can also be done.
Indications
• Diagnostic skin biopsy – used to confirm a clini- cal diagnosis or aid in the establishment of a diag- nosis.
• Excision biopsy – used in the treatment of skin lesions particularly epidermal or dermal neoplasm or to remove lesions for cosmetic reasons.
• It could also be done in some situations, when a clinical diagnosis is not in doubt, to reassure the patient that the clinician is taking an interest in his or her condition.
Relative contraindications
• Infants – although local anaesthetic creams/gels make this easier
• Thrombocytopenia – to avoid uncontrollable bleeding
• Lower limbs in elderly patients, skin abused with topical steroids – poor healing may occur
•
Upper trunk – to avoid keloid formation
Methods of skin biopsy
• Elliptical biopsy – Using the scalpel, the skin is cut with the long axis following the natural crease lines of the skin then sutured. This is most commonly used for diagnostic and excision skin biopsy.
• Punch biopsy – Uses the biopsy punch which is a sharp cutting edge, metal cylinder of variable di- ameter attached to a plastic handle. Ideal for inci- sion biopsy and excision of very small lesions.
• Shave biopsy – used in certain superficial benign papular or nodular lesions. Lesions are shaved off with acceptable cosmetic result. Haemostasis is achieved by cauterization or use of aluminium chloride hexahydrate. Recurrence is common.
The following equipment should be prepared
• Clean dressing trolley or appropriate clean surface.
• Skin Biopsy Pack or a sterile dressing pack containing sterile non-woven swabs and a sterile towel.
• Correctly labeled specimen pot containing the appropriate medium. This is decided by the type of investigation required.
• A sterile occlusive latex free dressing.
• Wound closure strips.
• Needles and syringes.
• Disposable punch biopsy needle if required.
• Disposable scalpel.
• Sterile gloves.
• Disposable plastic apron.
• Alcohol based antiseptic cleaning solution, e.g. Chlorhexidine Gluconate 0.5%.
• Local anaesthetic, e.g. Lidocaine 1%. (Lidocaine with Adrenaline (Epinephrine) which is a powerful vasoconstrictor, therefore decreasing bleeding in wounds. However this may be contraindicated in areas of end artery flow i.e., fingers and toes. This can cause palpitations and tremors, so is therefore used with caution.