Excisional biopsy

An excisional biopsy is planned after considering the local anatomy. The excision’s axis depends on the skin creases (Fig. 2) and its margin on the nature of the lesion. The ellipse to be excised is drawn on the skin using a marker pen. An ellipse has an apical angle of about 30° and is usually three times as long as it is wide. If any shorter, ‘dog-ears’ appear at either end, although these can easily be corrected. After cleaning, local anaesthetic is infiltrated using a fine needle into the area of the lesion. Once numbed, the skin is incised vertically down to fat with the scalpel, in a smooth continuous manner to complete both arcs of the ellipse. The ellipse is freed from surrounding skin, secured at one end with a skin hook and removed from the underlying fat, usually using the scalpel blade (Fig. 3). In most cases, the wound can now be repaired, although any bleeding vessels will need to be stemmed with cautery, hyfrecation or suturing.

Fig. 2 Facial crease lines, with some examples of excision ellipses.

Fig. 3 Ellipse removal and suture insertion.

(a) The ellipse is removed, one end being secured with a skin hook. (b) The suture needle is inserted vertically through the skin surface. (c) The suture needle pierces the full thickness of the epidermis and dermis. (d) The tied suture is ‘flask’ shaped and slightly everts the skin surface.

In a simple interrupted skin suture, the needle is inserted vertically through the skin surface down through the dermis and up the other side of the incision to trace a flask-shaped profile (see Fig. 3). The wound is apposed and slightly everted. Stitches should not be tied too tightly. Nylon or polypropylene sutures are tied with three knots in alternating directions to produce a square knot. Care is exercised at sites where keloids may form (e.g. the upper back, chest or jawline), where scars may be obvious (e.g. the face of a young woman) and when healing may be poor (e.g. the lower leg). In cosmetically sensitive sites, running subcuticular stitches are preferable.

Incisional, punch and shave biopsies

An incisional biopsy is done for diagnostic purposes. The technique is similar to an excision except that less tissue is taken. A punch biopsy is a sharp circular blade, which is twisted and gently pushed into the skin to create a vertical cylindrical defect (normally 4 mm in diameter) and is used for removing small lesions or for diagnostic biopsies (Fig. 4).

Fig. 4 Punch biopsy.

After anaesthetizing, the skin is stretched at right angles to the tension lines, the punch blade is placed on the skin over the area to be biopsied and rotated under gentle pressure by rolling it between the thumb and the forefinger until it penetrates down to subcutaneous fat. The full-thickness cylinder of skin floats up and can be snipped off at the base. The defect is repaired with a single suture, cauterized or left to heal by secondary intention.

Shave biopsy is employed for protuberant benign lesions, usually intradermal naevi or seborrhoeic warts. The lesion is shaved off parallel to, but slightly above, the skin surface. Haemostasis is achieved with cautery or hyfrecation. Not all the lesion is removed, and shaving is not used if malignancy is a possibility. Skin tags can be removed by simply snipping them off with scissors and cauterizing any bleeding points.

Curettage

Curettage is performed for seborrhoeic warts, pyogenic granulomas or single viral warts (e.g. on the face), but not for naevi or possibly malignant lesions. Basal cell carcinomas can be treated by repeated cycles of curettage and cautery but careful case selection is required. After being anaesthetized, the lesion is removed by a gentle scooping motion with the curette spoon or ring (Fig. 5), and then the base is cauterized. Curettings should be sent for histological analysis in 10% formalin.

Fig. 5 Curettage.

The lesion is removed using the curette spoon in a gentle scooping fashion. Most of the curettes now employed are disposable (use only once) ring curettes.

Cautery

Cautery secures haemostasis and destroys tissue. The conventional cautery machine has an electrically heated wire and is self-sterilizing. The Birtcher hyfrecator, a unipolar diathermy, gives better controlled electrocautery. It is used to treat spider naevi and telangiectasia, and to give haemostasis, but should not routinely be employed in patients with cardiac pacemakers. Aluminium chloride 20% in an alcohol base (Driclor; Anhydrol Forte) or silver nitrate sticks provide chemical cautery.

Cryotherapy

Cryotherapy using liquid nitrogen is effective for viral warts, molluscum contagiosum, seborrhoeic warts, actinic keratoses, in situ squamous cell carcinoma and, in some instances, biopsy-proven basal cell carcinoma. The liquid nitrogen (at −196°C) is delivered by spray gun (e.g. Cry-Ac) or cotton wool bud and injures cells by ice formation. After immersion in a flask containing liquid nitrogen, a cotton wool bud on a stick is applied to the lesion for about 10 s until a thin frozen halo appears at the base. The spray gun is used from a distance of about 10 mm for a similar length of freeze (Fig. 6). Longer freeze times are given for suitable malignant lesions. Blisters may develop within 24 h. They are punctured and a dry dressing applied. Side-effects include hypopigmentation of pigmented skin and ulceration of lower leg lesions (not recommended in this site), particularly in the elderly. Treatment is repeated after 4 weeks if necessary.

Fig. 6 Liquid nitrogen treatment using a cryotherapy apparatus.