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Skin lesions

Surgery

Objectives

  • Describe the use of topical and infiltrated local anaesthetics.
  • Describe primary excision and closure of a small skin lesion.
  • Know the indications for electrosurgery.

Key points

  • Where possible, an excision should be parallel to natural skin creases and wrinkles.
  • Scarring may be conspicuous in childhood, in dark skinned individuals and in certain sites such as the upper sternum.
  • Haematoma, infection and wound dehiscence increase scarring.
  • Emla is a topical anaesthetic cream applied an hour or two prior to removal of superficial skin lesions.
  • The addition of adrenaline 1:100,000 to lignocaine prolongs its duration, reduces toxicity and controls bleeding.
  • The maximum safe volume of 1% plain lignocaine in an adult on a single occasion is about 20ml.
  • Suspicious pigmented lesions should be removed with a 2-3mm margin of clinically normal skin.
  • Non-melanoma skin cancers on the face are best referred to a dermatologist or plastic surgeon. Elsewhere excision margins should include 4mm of clinically normal skin.
  • Sutures should be removed 4 to 7 days after the procedure from the face and 7 to 14 days elsewhere.
  • Mohs micrographic surgery is used for primary and recurrent non-melanoma skin cancer in high-risk areas.
  • Haemostasis can be obtained by localised pressure, using chemical haemostatic agents, electrosurgery or ligature of the bleeding vessel.
  • Electrosurgery is used for haemostasis and desiccation of tissue using high-frequency (0.1-1 MHz), high voltage, low-amperage currents in a modulated manner.
  • Electrocautery uses red-hot wire to burn the tissue.

Introduction

The surgical management of benign and malignant skin lesions ranges from a simple shave biopsy to complex excision and reconstruction, depending on the size and location of the lesion.

The aim is for minimal scarring. To achieve this, the excision should occur at right angles to the direction of the resultant pull of the muscles or parallel to natural skin creases and wrinkles – the more creases and wrinkles the less obvious the scar.

More conspicuous scarring arises in the following circumstances:

Hypertrophic scar on sternum (coronary artery bypass procedure)

Hypertrophic scar arose after surgical wound became infected

Conspicuous scarring following gravel abrasions


Anaesthesia

See local anaesthetics, DermNet.

Topical anaesthesia may be useful for:

This may be delivered as freezing spray at the time of the procedure (ethyl chloride, nitrous oxide or very light liquid nitrogen), or as a cream applied an hour or two earlier – such as eutectic mixture of prilocaine and lidocaine (Emla).

Most skin procedures require intradermal anaesthetic. Lignocaine, an amide, is most commonly used. The onset of action is rapid (one to two minutes) and it lasts one to three hours. The addition of adrenaline 1:100,000 prolongs its duration, reduces toxicity and controls bleeding. The adrenaline should not be used for circumferential block of a digit or penis, or in those with impaired peripheral circulation or serious heart disease.

The maximum safe volume of 1% plain lignocaine in an adult on a single occasion is about 20ml (detailed safety information can be found on manufacturers’ data sheets on the Medsafe site).

Vasoconstriction caused by local application of EMLA

Infiltrating local anaesthetic prior to skin biopsy


Elliptical excision and closure

Many general practitioners perform minor surgery for benign and small malignant skin lesions. Refer patients with large lesions or lesions on the face to a dermatologist or plastic surgeon for management. First, obtained the patient’s informed consent for the procedure (generally in writing).

Suspicious pigmented lesions should be removed in a fusiform shape with a 2-3mm margin. Small non-melanoma skin cancers should be given a margin of 4mm as the tumours are generally larger than clinically evident.

Instruments typically used for excision of a 0.5 to 1cm diameter skin lesion

Identify the margin of the lesion in a good light using magnification. Use a surgical pen to mark out the excision ellipse, which should be two or three times as long as it is wide and follow the lines of least tension.

Infiltrate with local anaesthetic, (usually 2% lignocaine with adrenaline) using a short (half- to one-inch) and fine needle (27-30 gauge) injected into the superficial dermis. Generally, 0.5ml is sufficient to anaesthetise an area of about 1cm2.

Scrub up and don surgical gloves and gown. Cleanse the surgical area with povidone iodine, chlorhexidine or alcohol solution. Apply surgical guards for aseptic technique.

With one hand, stabilise the incision area by traction. Using controlled pressure on the scalpel, cut along the marked lines vertically. Dissect down to mid subcutaneous tissue, and remove the specimen. The specimen should be placed in formol saline and the pot marked with at least the patient’s name and the site of the lesion.

If necessary, use blunt-tipped scissors undermine the skin edge by about 5mm below the dermis to free up the overlying skin to allow suturing without tension. Obtain haemostasis. Close the wound in a single layer using simple interrupted loop sutures tied using the needle holder, inserting and removing the needle in the line of its curve. There should be an equal “bite” of each side including at the least the whole dermis. Tie the knot so the edges of the wound are lightly in contact and slightly everted.

Deeper larger wounds may require insertion of interrupted absorbable subcutaneous sutures to eliminate dead space (which enhances the chance of haematoma and infection).

Apply light pressure to ensure bleeding has completely stopped, and apply a protective dressing for at least 24 hours. Typically, smear petroleum jelly over the excision line and apply a non-adherent hypoallergenic adhesive dressing. A waterproof dressing may be preferred.

Marking out area to excise

Prior to applying dressing


Advise the patient regarding wound care. In most cases, the first dressing should be removed at 24 hours and the wound should be gently cleansed with tap water. Dressings are then used if required to protect the wound from injury.

Sutures should be removed very gently as soon as possible (to avoid suture marks), using scissors or a scalpel blade and fine dissecting forceps. The number of days after the procedure depends on body site, the size of the wound and the amount of tension on it:

Mohs micrographic surgery

The indications for Mohs surgery are:

If a Mohs surgeon is unavailable, these lesions are removed by standard techniques.

Mohs surgery is performed under local anaesthesia. The majority of the lesion is first removed using a curette (a sharp spoon-shaped instrument). An intact two to three millimetre layer is then taken around the margins and under the base of the tumour. The specimens must be precisely orientated, divided, colour coded and mapped then processed by taking horizontal sections. It allows identification of any remaining tumour on the slide, the map and patient so that a second stage of excision can be specifically directed at residual tumour. The process is repeated until the tumour is clear without removing unnecessary unaffected skin.

The wound may be left to heal by secondary intention but is more frequently reconstructed.

Haemostasis

Methods of haemostasis include:

Electrosurgery

Electrosurgery is used for haemostasis and desiccation of tissue using high frequency (0.1-1 MHz), high voltage, and low-amperage currents in a modulated manner. It should in general be avoided in those with pacemakers although modern units are probably quite safe in stable patients providing the path of the electric current does not pass through the heart.

For sterility, disposable tips or needles are used with the hand piece inserted in a sterile glove or specific polythene casing. Reusable tips should be sterilised in an autoclave.

Methods include:

Alternatively, electrocautery uses red-hot wire to burn the tissue.

Skin lesion Electrosurgical method
Skin tags, warts, syringomas Gentle electrodessication prior to curettage
Telangiectasia Fine needle electrode and very low power electrodesiccation
Small non-melanoma skin cancers Dermatologists: Shave &/or curette the lesion prior to electrofulguration / desiccation or cautery (always send specimen for histology)

Tray set out for curettage and diathermy

Curetting out the lesion

Electrofulguration to base of lesion