Skin lesions are easily accessible for removal or biopsy.
The procedure used needs to be appropriate to the site and type of lesion involved.
It is important also to keep scarring to a minimum.
Destruction of skin lesions is carried out with:
• Electrocautery
• Cryotherapy
• Laser treatment
This is suitable for lesions where the diagnosis is certain, as no specimen is available or histology.
Removal of skin lesions results in a specimen for the pathologist to examine.
The techniques used are:
• Curettage and cautery
• Surgical excision
• Incisional biopsy which provides a specimen for histology to supplement the clinical diagnosis.
Cryotherapy
This involves the destruction of tissues by extreme cold.
Current methods used are:
Carbon dioxide
Solid carbon dioxide (temperature 64°C) is produced by allowing rapid expansion of the compressed gas from a cylinder.
This can be mixed with acetone to form a slush that can be applied with a cotton wool bud.
A solid carbon dioxide stick, for direct application to lesions, is produced by an apparatus using “sparklet” bulbs.
The lesion must be frozen solid with a 1–2mm margin of surrounding tissue.
After thawing the freezing cycle should be repeated. Liquid nitrogen ( 196°C)
This can be simply applied using a cotton wool bud dipped in the vacuum flask of liquid nitrogen.
Freezing takes a little longer than using spray apparatus.
Various types of such apparatus are available with different sizes of nozzle.
The larger ones are used for seborrheoic keratoses on the back, for example, and the smaller sizes for small lesions on the face.
Freezing takes a few seconds and after thawing a further application can be made if necessary.
Ethyl chloride
This is sprayed directly on the skin, producing lowering of the temperature and temporary analgesia.
It is not generally used for treatment.
Nitrous oxide
A cylinder of compressed gas is used to cool a probe to approximately 80°C.
It is usually used for the treatment of warts and requires a 30 second freezing cycle.
Precautions
• Cryotherapy produces pain and inflammation.
Blistering and haematoma may occur.
This can be diminished by the application of a strong steroid cream immediately after freezing, except when treating viral warts as it tends to encourage proliferation of the warts.
• Damage to deeper structures is rare but may occur when freezing the deeper tissues for example, treating basal cell carcinoma.
• It is possible for adjacent structures to be damaged accidentally, especially with the liquid nitrogen spray.
This applies particularly when treating lesions on the face, when it is essential to screen the eyes adequately.
Skin lesions suitable for freezing
Viral warts
These may require several treatments at two to three week intervals.
Freezing very small plane warts can result in small depigmented areas, so they may be better treated with wart paint.
Seborrhoeic keratoses
These respond well to cryotherapy, but as they are superficial lesions care must be taken to avoid excessive freezing with resultant scars.
Papillomata and skin tags
These can be easily and permanently treated by compression with artery forceps dipped in liquid nitrogen.
Surprisingly, this is generally a painless procedure.
Dysplastic lesions
Early lesions, which are potentially neoplastic or of low grade malignancy, can be effectively treated.
This includes solar keratoses, if early and superficial, but follow up is essential.
The lesions can progress to squamous carcinoma, and if not responding to cryotherapy they should be excised or removed with curettage and cautery for histological examination.
Bowen’s disease
An intraepidermal carcinoma, if confirmed by incisional biopsy, can respond to repeated cryotherapy.
Follow up is essential since progression to an invasive squamous carcinoma can occur.
Basal cell carcinoma
The superficial spreading type can be treated with liquid nitrogen, but repeated and often prolonged freezing is required.
To be certain of effective treatment a thermocouple probe to record the temperature at the base of the tumour is used.
This is not usually a routine procedure in general practice or hospital outpatients.
Excision or radiotherapy are more effective methods of treatment.
Electrocautery
There are two forms of treatment:
(1) Heat from an electrically heated element, which is used for removal of skin tags and for treatment of the surface after curettage of warts, also seborrhoeic keratoses.
(2) High energy, low current “electrodesiccation” equipment which produces a high energy spark that can coagulate blood vessels or destroy some more papillomata.
A fine needle point should be used for small telangiectatic naevi or milia.
A larger needle is used for larger surfaces, for example after curettage.
Laser treatment
Laser Light Amplification by Stimulated Emission of Radiation—produces high energy radiation.
The first laser apparatus was developed from microwave technology in 1960 by the nobel prize winner TH Mamian.
It was initially used as a destructive tool to ablate tumours, but now different wavelengths can be directed at specific targets.
Blood vessels, for example, take up the blue/green light of the argon laser and the red light of a ruby laser is well absorbed by the green dye of tattoos.
Modern developments have resulted in laser equipment that produces minimal scarring and maximum specificity.
Although smaller portable units are available, laser treatment should still only be undertaken by those with appropriate training.
The skin lesions most commonly treated by laser are described below.
Tattoos
Tattoos contain a variety of pigments so that more than one type of laser may be necessary for complete removal.
The same pigment may vary in response in different patients.
Superficial dark pigment usually responds to the Q switch ruby laser, but deeper pigment may require the Nd : YAG laser or Alexandrite laser.
Green pigment is usually removed with a Q switch ruby laser and red pigment with a green light laser such as the Q switched Nd : YAG.
It is found that professional tattoos are usually more easily removed than the amateur type.
Pigmented lesions
Melanin absorbs light over a wide range of wavelengths, which can result in undesirable loss of skin colour following laser treatment.
This can be put to good use in the treatment of benign lentigines and café au lait patches or deeply seated pigmented naevi.
A wide range of laser types can be used, including Q switch ruby and Nd : YAG lasers.
Congenital pigmented naevi should not be treated unless the biopsy has confirmed that they are benign.
Hair follicles
Laser equipment is available for removing excess hair and is a very effective cosmetic tool.
Laser surgery
Lasers can be used as a cutting tool and recent studies have shown them to be a very effective means of producing incisions in the skin.
Curettage
This is a simple way of removing epidermal lesions.
A curette has a metal spoon shaped end with a sharp cutting edge.
There are a variety of shapes and sizes suitable for different lesions, from large seborrhoeic keratoses or papillomata to smaller ones for minute keratin cysts.
A specimen is provided for histology but completeness of removal cannot be accurately assessed.
Local anaesthetic is used and, with the skin stretched, the curette is applied at the edge of the lesion which is then scooped off.
It is advisable to work around the edges of larger or more firmly attached lesions.
The dermis normally feels firm but when curetting off a keratotic horn or solar keratoses; a soft consistency may indicate dysplastic change.
The base can be lightly cauterised to control bleeding, sterilise the site, and prevent recurrence.
Various types of disposable curettes are available and are easy to use.
Incisional biopsy and punch biopsy
It is essential to have a working clinical diagnosis, but wherever there is doubt the pathologists can provide much more precise information regarding the nature and extent of the lesion.
For example, a patch of Bowen’s disease (intraepidermal carcinoma) may resemble sclerosing superficial basal cell carcinoma and a biopsy will usually distinguish them.
Similarly, what seems to be a dysplastic pigmented naevus clinically may, on the one hand, prove to be benign or, on the other hand, turn out to be a malignant melanoma requiring wide excision.
Immunofluorescent staining of a blistering lesion differentiates dermatitis herpetiformis, which is treated with a gluten free diet, from pemphigoid, which requires corticosteroids and often immunosuppressant drugs.
Incisional biopsy
This is suitable for larger lesions and is taken across the margin of the lesion in the form of an elipse.
It is essential to include deeper dermis, as the significant changes in, for example, granuloma or lymphoid infiltrate may not be near the surface.
An adequate amount of normal tissue should be included, so this could be compared with the pathological area and this also means there is enough normal skin to suture the incision together.
Punch biopsy
The biopsy tool consists of a small cylinder with a cutting rim which is used to penetrate the epidermis by rotation between the operator’s finger and thumb.
There is minimal danger of damaging deeper structures as the elastic subcutaneous tissues merely rotate with the tool without being cut.
The resulting plug of skin is lifted out with forceps and cut off as deeply as possible.
With the smaller sized punches the resulting defect can be treated with electrocautery or left to heal spontaneously. With a punch larger than 3 or 4 mm a single suture can be used.
The main disadvantage of a punch biopsy is that it only provides a single small piece of tissue. It may not be representative or may miss an area of substantial change.
It tends to leave a more prominent scar than the incisional biopsy.
Excision of skin lesions is both curative and diagnostic.
It may be the best way of making a diagnosis if there are multiple small papules or vesicles, one of which can be excised intact.
Incisions should follow tension or wrinkle lines.
In the case of malignant lesions it is particularly important that the whole lesion is adequately excised.
The pathologist can report on the adequacy of excision, but not in multifocal basal cell carcinoma where this cannot be assessed.
If there is likely to be any doubt about the excision being complete it is helpful to attach a suture to one end of the excised specimen so the pathologist can describe which border, if any, extends over the excision margin.
Technique
The basic technique consists of making an elliptical incision with the length three times the width.
This enables suturing without the formation of “dog ears” at the end.
The long axis of the excision should follow the “wrinkle lines” of the skin, which are parallel to the collagen bundle in the dermis.
This produces stronger, narrower scars.
They are not the same as the deeper lines or fasical attachment or “Lange lines”.
Lesions on the sternal area, upper chest, and shoulders, where keloid scars often form, should only be excised when it is essential and may be best referred to a plastic surgeon.
Local anaesthetic is injected subcutaneously but close to the skin.
The incision should be vertical rather than wedge shaped. Monofilament sutures cause less inflammation and trapping of serum than the braided variety, but are harder to tie securely.
Methods of suturing and the more specialised techniques of flaps and grafts are outside the scope of this book.
It is an asset for the dermatologist to be able to carry out surgical procedures on the skin and suitable courses are generally available.
