A Quick Guide to Skin Biopsy

Sampling Skin Lesions on the Foot

A biopsy is a medical procedure that involves taking a small sample of body tissue so it can be examined under a microscope (NHS). There are several ways a sample is taken.

The skin, being both visible and superficial to other structures, often shows changes that make it difficult to decide whether there is a change that leads to concern. The key areas that are easily missed include under the nail or between the toes.

As we age, reaching and seeing the foot can be challenging because of its limitations due to inflexibility. The sole can hide blemishes, while swellings can at least be felt by hand.

The good news is that the foot, while having many blemishes, does not present life-changing problems that are as common as we might believe. The last thing any responsible professional wants is a stampede of pointless referrals, wasting time on one hand and not dismissing worry on the other.

However, the skin often shows more cancer than deeper parts, such as bone, joints, or muscles. Cancer does not have to be life-threatening, and some cancers are slow to develop and can be managed. 

The key signs of abnormal changes include an area that changes colour, bleeds, itches, changes shape, or alters the surrounding border. We call any change from normality a LESION.

Any change in a lesion should be photographed, dated, and followed carefully. If the lesion changes, an early consultation is required. Phone the GP practice and tell the reception staff that you have an area that has changed on your foot and would like to see someone.

Today, 111 is a direct helpline to the NHS (UK), and someone will guide you if you cannot see a GP. Podiatrists can also guide you, and many have now introduced special diagnostic tests such as dermoscopy to improve diagnosis and classify whether a referral or a biopsy is required. We do not want to cut into the skin unless necessary, and then we need to confirm our suspicions and provide treatment. Treatment can range from heat or cold to laser, cryotherapy, or surgery.

The dermatoscope. Click on the image to see the difference between this and a magnifying glass.

Surgical Skin Biopsy

The surgeon has several techniques available. We can shave the top to acquire a sample, or we can punch a section out with a small punch. The last technique is an excisional biopsy, which is often used as part of treatment.

Shave, punch, and excisional biopsy are different techniques. The biopsy is designed as a diagnostic method for testing for abnormal skin cells. Sometimes needles are used, and the technique is called a needle biopsy, but, for the most part, we use needles to draw fluid for sampling for infection and gouty crystals seen in joints.

Preparation

Local anaesthetic is used mainly for these outpatient-based procedures. This means you can go home after the procedure has been completed. Pain medication is recommended if the area is likely to be sore or if more than one sample has been used. The skin or cell samples are placed in a pot and sent off to the laboratory to be viewed and reported on. The sample is carefully handled, and then slices are cut so that it fits under a microscope on a glass slide. Simple samples are usually returned within a week, although it depends on the urgency stated by the clinician. 

1- Shave

Video of shave biopsy is often used for lesions that stick up and have thin stalks. They are not ideal for lesions that involve deeper structures. As a podiatric surgeon, I would prefer to remove the whole lesion, taking some healthy tissue with the sample. One of the things I learned when training was that my consultant pathologists would scribble all over the report that an insufficient sample was taken. This is embarrassing for the clinician, and of course, the patient may have to come back for a repeat procedure. The reason that pathologists would rant was that they needed healthy side tissue to make a reasoned comparison. 

The author is taking a punch biopsy. (C) Tollafield DR

2- Punch

A punch biopsy is generally better for flat lesions that have depth. These are valuable because the site heals quickly. The sampling technique is fast and can reach down to the bone to ensure the pathway is free of abnormal cells.

The diameter varies with these punch biopsies from 4 mm upwards. I found I could punch through a nail so as not to remove the nail plate, which is better for the patient. One of the problems with punches is that if the diameter is small, you may not capture the edge where healthy tissue exists, invoking an angry scribble on the report! Smaller punches can prove difficult to retrieve the sample.

Sutures are less likely than with excisional biopsy, but of course, as the diameter widens, closure may require a suture. The following link is valid and offers some more material. Click here. The YouTube film may be helpful for students and those with stronger constitutions.

Click on the image for the video. Punch biopsy

3- Excisional

Excisional biopsy is the standard for lesions in general for two reasons. It provides visual depth, and the surgeon can assess the changes in tissue, offering a high suspicion of concern or not. The lesion can be excised to give a good sampling of normal tissue. The closure is made with steristrips (tapes) or sutures. It is, in effect, a surgical procedure and must be carried out to the same standards as any surgery.

 This 35-second video helps the uninitiated to understand this technique.

Summary

Three techniques have been described and shown, each with a specific indication and benefit for sampling skin lesions on the foot. For the clinician, planning is essential, and larger areas of excision are best performed in a dedicated theatre environment.

The use of dermoscopy has reduced the immediate need for surgical biopsy where the lesion may be unclear to diagnose. Remember, most lesions are harmless and take time to develop problems. However, if the site is painful, itching, changing colour, bleeding, or discharging, or the border has lost shape, then it is essential to obtain a medical opinion early.

The foot may be hidden, but it can be exposed to the sun. The skin may burn when on the beach or outside in the open. Injuries that may appear to heal partly can turn nasty, and infections, if left, can also alter the skin cells and become malignant.

Thanks for reading ‘Biopsy in the Foot’, a short introduction to the benefits of biopsy in the foot by David R. Tollafield

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