Skin surgery & therapy 1

The bulk of the rest of skincancer909 is going to deal with clinical diagnosis, and the various clinical presentations you need to be familiar with. But first, I need to take you on a brief detour into some of the basic aspects of skin surgery. Why discuss therapy before diagnosis? Simply, because across different tumour types, we use a common handful of surgical techniques, and since we match therapy to the behaviour of a particular skin cancer, we first need to learn some of the basic surgical and therapeutic terminology. Trust me, it is easier this way — but we will revisit some of this content in the later skin surgery and therapy chapters.

We need to think about the tool we are using for the surgical task and understand the difference between incision and excision.

The image above shows a scalpel — essentially a knife, so I will say little more abut this— and a punch biopsy and a ring curette. The punch biopsy is a circular sharp blade that is useful for obtaining cylindrical samples of skin. You use it by quickly rotating the tool ‘too and fro’ (alternating clockwise and anticlockwise movements) with a firm downward pressure. The instrument is held perpendicular to the skin’s surface. The core of skin can then be detached from the deeper structures using scissors or a scalpel and sent for histopathological examination.

The ring curette is used differently. The edge is sharp and the instrument is pulled across the lesion in a direction parallel to the skin’s surface. It is akin to scratching with a razor-sharp fingernail. It will tend to produce fragments of tissue, but the normal architecture of the lesion will be damaged. Again, the contents can be sent for histopathological examination. A curette is useful, but after reading the previous sentences you may realise some of  its drawbacks.

Biopsy 1 is an excision — the whole of the lesion has been removed, and a scalpel was used to generate an ellipse (an ellipse shape makes apposition of the wound edges easier for the repair).

Biopsy 2 is also an excision (all the lesion is removed) but represents what might be possible for a very small lesion with a punch biopsy (a circular blade). In both Biopsy 1 and Biopsy 2, the intention was to remove all of the lesion, and the adequacy of this excision can be checked by histological examination.

By contrast, Biopsies 3, 4, and 5 are all incisional biopsies — the goal was not to remove all of the lesion, but obtain a diagnosis. Biopsy 5 might have been taken with a punch biopsy and may provide a sample adequate for the dermatopathologist for some tumours. Biopsies 3 and 4 include some normal tissue, and such sampling can be important to diagnose some rashes (or tumours) where the change from normal to abnormal is important. Large incisional biopsies ‘across the lesion’, such as in Biopsy 3, may also be necessary for the diagnosis of some large tumour types.

Sometimes, a technique called shave biopsy is used, usually using a scalpel. Here, as in example 1 below, the aim is not to remove all of the lesion merely to obtain a small sample for histological examination; or to remove ‘most of the lesion’. Obviously, such a technique is not appropriate unless the diagnosis is certain — you would not use this technique for a suspected melanoma.

Sometimes, in some body sites especially if they are convex, you may be able to deliberately excise a lesion using the shave technique (example 2).

If an excision is performed and the wound edges pulled together and the site closed, this is a primary closure. On some occasions it is not possible to pull together the edges (the surgical defect is too large), but it may be possible, especially at concave sites, to allow the wound to heal ‘from the base up’. This is referred to as secondary intention healing. Close attention has to be paid to postoperative dressings and care, but the result in some sites is superior to that obtained from a graft or flap (see below).

Most skin cancers can be treated with simple excision and primary closure (that is, bringing the wound edges together with side to side closure, using sutures). However, sometimes the surgical defect is so large, that a more advanced repair may be required, because it is not possible to close the defect by primary closure.

There are two terms you should know. Skin grafts are samples of skin taken from elsewhere on the body, detached from their blood supply, and used to ‘fill’ the defect. Flaps are donor areas of skin that keep their connection with their origin, and therefore have a blood supply, and are ‘moved’ such that the defect can be covered. In some flaps the connection with their origin will be later divided (‘broken’).

the difference between flaps and grafts relates to whether the donor is detached from its blood supply

There are many factors that influence whether grafts or flaps are used in any particular situation. Flaps generally require more skill, but are not always feasible.

One issue with grafts, is that because donor and defect sites are from different skin regions, the donor skin may not match the recipient site well leading to a poor aesthetic outcome (see image above).

The UK law on consent has recently changed. The Montgomery judgement rules that ‘the doctor is under a duty to take reasonable care to ensure that the patient is aware of any material risks involved in any recommended treatment, and of any reasonable alternative or variant treatment’. So now it is the patient rather than doctors who decide on the level of risk they wish to take in a particular situation, having been provided with all the relevant information.

A useful acronym to use in the consent process is PARQI:

• Procedure (what is involved?)
• Alternatives (what other ways of managing the condition are there?)
• Risks (what may go wrong?)
• Questions (consent is only meaningful if there is an opportunity to ask questions)
• Information leaflet (if available, use)

Using language the patient can understand, the procedure should be explained along with the alternatives. Surgical risks include:

• infection
• bleeding
• scarring
• recurrence
• nerve damage

Questions should be invited and an information leaflet provided. This should all be clearly documented in the notes.

Wrong site surgery is regarded as a ‘never event’. A never event is a ‘serious, largely preventable patient safety incident that should not occur if existing national guidance or safety recommendations had been implemented by health care providers’. There is no defence for wrong site surgery and it is virtually impossible to succeed in getting a surgeon to be declared not liable in cases of wrong site surgery. Ways of reducing wrong site surgery in dermatological surgery include:

• photography of the index lesion referred for surgery
• using a hand held mirror or mirror to identify the correct lesion for areas on the face or the back with the patient
• using accurate anatomical descriptions and landmarks

1% Lignocaine (Xylocaine) with adrenaline 1:200 000 is routinely used in skin surgery. The safe recommended dose of plain lignocaine is ~200mg (3mg/kg), which allows 20ml for a 70kg adult. When adrenaline is added, up to 500mg (~7mg/kg) can be used, which is ~50ml for a 70kg adult. The advantage of adrenaline is that it causes vasoconstriction assisting with visualisation of the surgical field. Lignocaine with adrenaline can be safely used on the nose and ears. It can also be safely used for digital ring blocks in healthy patients. In patients with severe peripheral vascular disease or Raynauds, plain lignocaine should be used for digital ring blocks to prevent the risk of digital necrosis.

Adrenaline in local anaesthetic can be used safely in mid to late pregnancy without altering uterine blood flow. There is no evidence that using small doses (<5ml) of lignocaine with adrenaline in the first trimester causes foetal harm, but it’s prudent to delay non-urgent surgical procedures until after this period.

There are no reports in the dermatology surgery literature of patients dying from a post surgical haemorrhage  having continued anticoagulants. There are reports however of individuals having catastrophic embolic events, resulting in death, who had stopped anticoagulants for skin surgery. We therefore do not routinely recommend discontinuing single agent anticoagulants. Patients taking warfarin should have an INR 24-48 hours pre-op and provided this is less than 3.5 then surgery can proceed, although the risk of bleeding is increased especially for complex procedures.

If a patient is on a single antiplatelet agent, such as aspirin or clopidogrel, it is not normally necessary to stop it. If the patient is on two agents, the increased risk of bleeding versus risk of an embolic event should be discussed with the patient and their other physicians. Stopping of these agents if thought necessary needs to be done 7 days preoperatively.

Cryotherapy is a popular and useful treatment for many premalignant lesions and occasionally for some malignant keratinocyte tumours. Do not use cryotherapy if you are uncertain of the diagnosis.

Liquid nitrogen at a temperature of -196C is sprayed onto the skin’s surface. The aim is for rapid freezing, followed by slow thawing. More than one round of freeze/thaw may be needed.To be effective the lesion temperature should drop to -55C. This causes intracellular and extracellular cell damage and vascular injury. Cryotherapy is painful, and is followed by inflammation, and possibly blister formation, ulceration and scarring. Cryotherapy of lesions on the hands may lead to tendon rupture or damage to the ulnar nerve.

Radiotherapy used to be the most commonly modality of treatment for BCC and many SCC. Today it is used much less commonly. In general, surgery is more effective. Radiotherapy still has a key role as a post-surgical therapy for some high risk non-melanoma skin cancer.

1. What is the difference between a flap and a graft?
2. Are all shave biopsies incisional?
3. Why might you use secondary intention healing?
4. Can you use a punch biopsy for an excision biopsy?
5. What do you think are the potential drawbacks of curetting a lesion?
6. Name three side effects of cryotherapy.
7. Why is adrenaline an advantage in local anaesthetics?
8. Lignocaine with adrenaline is contraindicated on the nose or ears. True or false?
9. Should warfarin or other anticoagulants be stopped prior to skin surgery?
10. What does PARQI stand for?

A PDF  containing the above questions and the answers is here. The video talkover below goes through the questions and answers in greater depth. 

Skincancer909 by Jonathan Rees is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Where different rights apply for any figures, this is indicated  in the text.