Skin biopsies are an integral part of the skin cancer diagnostic process, but they are also used for other skin conditions. Usually, we can diagnose a skin condition or a rash just from clinical examination and a careful history, but there are those times when we just cannot find the diagnosis. This is when a skin biopsy might be of benefit.

Skin biopsies are performed to help diagnose and plan treatment

They are generally not used to ‘treat’ the lesion, although sometimes you may get lucky and they actually remove the skin cancer by themselves. They are used to find out what skin condition or skin cancer you have, and therefore allow your doctor to plan the treatment that you need properly.

There are multiple types of skin biopsy, but they are all done for the same reason – to help diagnose the condition affecting the skin.

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Skin biopsies are done to aid in the diagnosis of skin conditions, including skin cancer, and we have different ways of doing them.

Skin Scraping

Not a biopsy as such, but these are often done for likely fungal infections. Usually, a scalpel blade is used to very lightly scrape the surface of the skin into a specimen jar and it’s then sent to the pathologist to test. This doesn’t usually hurt at all and doesn’t require any anaesthetic or dressing afterwards, or any special aftercare.

Time: very quick
Cost: quickest and therefore usually no extra coast
Used for: skin conditions e.g. suspected fungal infections
Anaesthetic: not needed
Aftercare: none specifically

Punch Biopsy

A punch biopsy pen is used to ‘punch’ a segment out of the skin. This is done with local anaesthetic as it uses a cylindrical scalpel blade to core out a piece of skin. Depending on the size of the biopsy taken, it may or may not require sutures (stitches). Usually, if it’s less than 6mm in diameter it will not require suturing, however on some parts of the body (e.g. lip) they can bleed a lot and so may benefit from a stitch anyway.

A local anaesthetic is injected around the biopsy site, then the biopsy is taken when the area is numb. Bleeding will be stopped by either electrocautery (the buzzer), chemical cautery or pressure. Personally I usually use Stingose gel to stop the bleeding. The aluminium sulphate in there cauterises the bleeding when agitated for around 15-20 seconds. My patients report anecdotally that they feel it gives better scarring and less irritation than electrocautery, though this is unproven.

The sample is sent to the lab, and after bleeding has stopped a suitable dressing is applied. Usually, I would apply a small layer of gel like Solosite, apply a small patch of alginate dressing like Algisite to help stop any bleeding that may occur later, and then a secondary dressing on top.

Punch biopsies are usually used on either small lesions (where you can actually just excise the whole thing with the punch) or on lesions that are just too big to biopsy in other ways. They are not usually used to diagnose skin cancers because they only test the part that was removed, not the whole lesion. If possible it is usually better to biopsy the entire lesion.

Time: quick
Cost: quick and therefore cheapest option normally
Used for: skin conditions or large skin cancers (multiple may be done)
Anaesthetic: local anaesthetic
Aftercare: dressings 24 hours usually. No sutures to remove.

Shave Biopsies

Using local anaesthetic to numb the area, part of the skin is ‘shaved’ off using either a scalpel or something like a dermoblade. Larger samples can be taken than the punch biopsy, although this is usually used for flat lesions. It can also be a good way to remove raised moles or benign lesions like seborrheic keratosis, although they can recur.

Advantages are they are quick to do, require little aftercare and heal fairly quickly (usually a few weeks for complete healing). The main disadvantage is that they generally should not be used for a potential melanoma unless the operator is skilled and experienced. The risk is that the melanoma can be transected (sliced through) which can greatly affect the accuracy of the results and diagnosis may be inaccurate.

Aftercare is similar to the punch biopsy. Usually, wounds can be exposed after only a few hours, although I usually suggest 24 hours of dressings.

Time: quick
Cost: quick and therefore cheapest option normally
Used for: flat skin cancers (or raised if the clinician is skilled and experienced)
Anaesthetic: local anaesthetic
Aftercare: dressings 24 hours usually. No sutures to remove.

Incisional Biopsy

If a lesion is too large to cut out, but we do not want to do shave or punch biopsies. For example, a suspected melanoma that is too large to remove in one pass. We may cut out part of it to send to the lab.

This has the same disadvantage as a punch biopsy, but less so given that we are taking more tissue for sending.

Only used on very large or difficult to biopsy lesions.

Time: medium
Cost: variable depending on lesion size
Used for: large skin cancers
Anaesthetic: local anaesthetic
Aftercare: dressings 24-48 hours usually. If sutures often 7-10 days to remove.

Excisional Biopsies

The gold standard of biopsies. Excisional means the entire thing is cut out, and usually, the defect (hole) is stitched back together. If the lesion is very small then this may be done with a punch biopsy tool and there may not be a need for sutures. Generally if above 6mm a suture will be needed.

This is the longest (time) form of biopsy as it is cutting the whole thing out and suturing it back together again.

Usually, a narrow margin will be taken, 1-2mm of healthy skin around. This is to make sure we have the whole thing to diagnose it properly. Despite this, this is not a definitive curative procedure and further treatment may be necessary.

Time: Longest
Cost: variable depending on lesion size, generally most expensive
Typically used for: Melanoma skin cancers
Anaesthetic: local anaesthetic
Aftercare: dressings 24-48 hours usually. If sutures often 7-10 days to remove.

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