Chapter 23
Practical Procedures and Skin Surgery

Raj Mallipeddi

Cutaneous Laser and Surgery Unit, St. John’s Institute of Dermatology, St. Thomas’ Hospital, UK

OVERVIEW

The object of physical treatments is to remove lesions and, if appropriate, to provide material for histological diagnosis.
Destructive methods of treatment include cryotherapy, electrocautery and laser treatment. Curettage both destroys the lesion and provides fragmented material for histology.
Cryotherapy involves the use of extreme cold to destroy the affected tissue. Solid carbon dioxide, nitrous oxide and ethyl chloride can all be used but liquid nitrogen is the most effective and commonly employed. It produces inflammation and may cause ulceration.
Electrosurgery is the use of electric current to destroy tissue by heat in two forms: electrocautery using a heated element and electrodessication using a high frequency alternating current.
Curettage is suitable for superficial lesions and is usually combined with electrocautery.
Specimens for histology can be part of a lesion or the entire sample. Usually only part of the lesion is obtained by incisional, shave and punch biopsies, and therefore, the resulting specimens do not give information on the extent of the lesion as compared to full excisions.
Surgical excisions require adequate training and knowledge of the management of skin lesions and correct surgical techniques to completely excise lesions while causing the least possible scarring.
This chapter focuses on the more conventional procedures undertaken in general practice.

Cryotherapy

This involves the destruction of tissues by extreme cold (Box 23.1). The tissue is frozen to subzero temperatures, which is then followed by sloughing of dead tissue. Several mechanisms are involved including the osmotic effects of intracellular water leaving the cell and causing dehydration, intracellular ice formation disrupting the cell membrane and ischaemic damage due to freezing of vessels. Liquid nitrogen is most commonly employed, although various freezing agents are available such as solid carbon dioxide, nitrous oxide and a mixture of dimethyl ether and propane. Unless otherwise stated the rest of this section relates to liquid nitrogen cryotherapy.

Box 23.1 Cryotherapy—practical points

Be confident of the diagnosis before treating any lesion with cryotherapy and if in doubt perform a biopsy or refer the patient to a specialist.
Monitor the freeze time, spray in short bursts to maintain an ice-ball and stop when the desired freeze time is over.
Warn patients about potential side effects including pain, redness, swelling and blistering.
Children do not tolerate cryotherapy well; therefore consider alternative treatments.

The low temperature of liquid nitrogen (−196 °C), ease of storage and relative low cost make it an effective and convenient cryogen. However, its low temperature also results in rapid evaporation and therefore it should be stored carefully in an adequately ventilated area and preferably in a pressurised container.

Application technique

The liquid nitrogen is best applied as a spray using a canister (Figure 23.1).

An alternative method is to use a cotton bud that is immersed in liquid nitrogen and then applied to the lesion being treated, using moderate pressure until frozen. More than one application may be needed. A fresh cotton bud should be used for each patient to diminish the risk of transferring human papillomavirus. However, with this method there in an increase in temperature partly due to poor thermal capacity of the cotton and also warming when the cotton tip is transferred from the liquid nitrogen container to the patient’s skin. The freeze time is important, and will vary according to the lesion being treated.

Freeze time is counted from the moment the entire lesion becomes frozen white rather than simply from when spraying begins. Once spraying is complete, the rate of thawing of the tissue is an important factor as more tissue destruction occurs with rapid freezing and slow thawing. The ‘freeze–thaw’ cycle may be repeated to increase the degree of damage and the additional freeze has a greater penetration due to improved cold conductivity of the previously frozen tissue. Freeze times and the number of freeze–thaw cycles depend on the type of lesion (i.e. whether benign or malignant) as well as the size and thickness.

Risks and precautions

Patients should be warned about reactions which can occur within the first 48 h after treatment such as pain, redness, swelling and blistering, so that they are not unduly alarmed. A potent topical steroid cream applied over the affected area for a few days can be used to limit this.
Ulceration may occur, particularly on the lower limb if there is poor perfusion.
Although secondary bacterial infection is rare, increased pain, redness or swelling after 2–3 days may be indicative of this.
Later risks include scarring and, particularly in darker skin types, hypopigmentation or hyperpigmentation. As might be expected, these are more of an issue with prolonged treatments.

Skin lesions suitable for freezing

Cryotherapy is usually initiated on the basis of a clinical diagnosis without prior histological confirmation, and therefore, the clinician must be confident of the diagnosis. If there is any diagnostic doubt, consider a biopsy first or alternative treatment modality where histology can also be obtained. The following lesions are frequently treated with cryotherapy.

Viral warts

A single freeze lasting 10–30 s per treatment, which includes a 1–2 mm margin of normal skin, is often sufficient, although a double freeze–thaw cycle may improve clearance, particularly for thicker warts. Usually several treatments at 2–3-week intervals are necessary and cryotherapy may be combined with topical therapies such as salicylic acid preparations for increased efficacy. Paring down the wart with a blade before cryotherapy can also be helpful.

Seborrhoeic keratoses

A single freeze of between 5 and 20 s including a 1- to 2-mm margin of normal skin should be effective for most lesions. A frozen lesion once thawed for a few seconds can also be curetted off. Larger, thicker lesions may require prolonged freezing or repeat freeze–thaw cycles, thereby increasing pain and inflammation. In these circumstances, it may be better to curette and gently cauterise the area.

Papillomas and skin tags

A single freeze of 5–10 s may be sufficient and it is helpful to stabilise the skin tag with metal forceps so that the liquid nitrogen is sprayed obliquely, avoiding non-lesional skin. An alternative method is to treat by compression with artery forceps dipped in liquid nitrogen.

Actinic keratosis

A single freeze of between 5 and 15 s including a 1- to 2-mm margin of normal skin is advised. When necessary, lifting away hard keratin to expose the underlying abnormal epithelium makes the freezing more effective. Rarely, a double freeze–thaw cycle may be needed but be aware that a lesion which does not respond to cryotherapy may be a squamous cell carcinoma.

Bowen’s disease

This is an intraepidermal (in situ) form of squamous cell carcinoma, which can be effectively treated with a single freeze of up to 30 s including a 1- to 2-mm margin of normal skin. Again, a biopsy is necessary should there be any doubt about the diagnosis, and follow-up is essential to make sure the lesion has cleared and is not progressing.

Basal cell carcinoma

If cryotherapy is to be employed, it is best limited to the treatment of the superficial type of basal cell carcinoma (BCC), when lesions are primary (i.e. previously untreated), small (<1 cm in diameter) and well defined. The cure rate for other types of BCC is inferior with cryotherapy than with other forms of treatment such as excision. Two cycles of freezing lasting between 20 and 30 s, including a 3-mm rim of clinically normal skin, with a thaw time of 2 min is effective.

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Practical Procedures and Skin Surgery

OVERVIEW

Cryotherapy