Skin biopsy

A skin biopsy involves taking a small sample of tissue for examination by a pathologist, which involves analysing the cells and tissue structure under a microscope. It can help to confirm or establish a diagnosis of various skin conditions and, in some cases, provide the information needed to classify them and decide on the next steps.

What is a skin biopsy and what information does it provide?

During a skin biopsy, a small sample of skin is taken from an area selected by the specialist. The sample is sent to the pathology department, where the structure of the tissue and the characteristics of its cells are examined under a microscope.

This analysis can help diagnose tumours, inflammatory or autoimmune diseases, infections and other skin conditions. Depending on what is being investigated, specific techniques may be used, such as special stains, immunohistochemistry, immunofluorescence, cultures or molecular tests.

The result does not always provide a single answer. It may confirm a diagnosis, point to several possibilities or, in some cases, be insufficiently conclusive.

To interpret it correctly, the pathologist needs to know which lesion was biopsied, where it was located, how it had progressed, and what treatments had been used.

Types of skin biopsy

The technique is chosen based on the size, location and depth of the lesion, as well as the information that needs to be obtained.

Shave biopsy

This involves removing the superficial part of a lesion using a blade or a specialised instrument. It may be suitable for certain superficial or raised lesions, but is not the technique of choice when it is essential to examine the full depth of the lesion.

Punch biopsy

This uses a circular instrument to remove a small cylinder of skin that may include the epidermis, dermis and part of the subcutaneous tissue. Depending on the size of the sample and the area, the wound may be closed with stitches or may heal without sutures.

Incision biopsy

This removes only part of the lesion. It may be used when the lesion is large or deep, or when it is not appropriate to remove it completely during the initial diagnostic procedure.

Excision biopsy

This procedure aims to remove the entire visible lesion. The term ‘excisional’ describes the intention to remove the entire lesion, but does not necessarily mean that treatment is complete. Subsequent analysis allows the nature of the lesion and its relationship to the margins of the sample to be assessed.

Why is a skin biopsy carried out?

It may be requested to examine pigmented or tumourous lesions and determine whether they are benign, precancerous or malignant. When a tumour is identified, the analysis can provide information about its type and other relevant characteristics to help plan treatment.

It can also help diagnose inflammatory and autoimmune conditions, such as certain types of psoriasis, lichen planus, cutaneous lupus, vasculitis or bullous diseases.

In these conditions, different processes can produce similar microscopic patterns. The result is therefore interpreted in conjunction with the distribution of the lesions, the symptoms, the course of the condition and the treatments used.

When an infection is suspected, the biopsy may reveal changes consistent with infection or enable specific tests to be carried out to identify microorganisms. In some cases, separate samples are required for culture or molecular techniques.

It can also be used to diagnose certain types of alopecia, nail disorders, panniculitis and conditions affecting the blood vessels or the tissue beneath the skin.

How the site and type of biopsy are chosen

The quality of the diagnosis depends largely on obtaining representative tissue. In the case of a tumour, it may be necessary to obtain a sufficient depth of tissue. In the case of an inflammatory condition, an active margin or a recent lesion may be more useful than an area that has been scratched, ulcerated, scarred or intensively treated.

The age of the lesion may also be a factor, as some diseases display their most characteristic changes at specific stages of their progression.

In some autoimmune diseases, two biopsies may be required: one for conventional microscopic examination and another for immunofluorescence, a technique that uses labelled antibodies to detect specific deposits in the tissue.

Where there are multiple lesions or it may prove difficult to identify the exact site later, a photograph or record of the biopsied area may be taken.

How to prepare for a skin biopsy

Most skin biopsies are carried out under local anaesthetic and do not require you to fast. Instructions may differ if sedation, a more extensive procedure or an operation in the operating theatre is planned. Before the test, you should inform the healthcare team about:

• Anticoagulants, antiplatelet agents, aspirin and other treatments.

• Allergies to anaesthetics, antiseptics, adhesives or latex.

• Diabetes, immunosuppression or previous problems with wound healing.

• A tendency to develop thick scars or keloids.

• Pregnancy.

• Creams, corticosteroids, antibiotics or antifungals applied to the lesion.

• Previous reactions to skin procedures.

Anticoagulants, antiplatelet agents or other medicines must not be stopped without medical advice. The healthcare professional will assess both the risk of bleeding and the potential risks of discontinuing treatment.

The team must also be aware of which products have been applied to the lesion and for how long, as some treatments may alter the microscopic appearance of the tissue.

How a skin biopsy is carried out

Before starting, the healthcare professional confirms which lesion is to be biopsied, reviews your medication and medical history, and explains what information they hope to obtain.

The skin is cleaned with an antiseptic and a local anaesthetic is administered – a medicine that numbs only the area to be treated. The needle prick and the injection of the anaesthetic may cause a stinging sensation or a feeling of pressure for a few seconds.

Before taking the sample, the healthcare professional checks that the area is sufficiently numbed. During the biopsy, you may feel pressure, movement, scraping or tightness, although the anaesthetic reduces any pain.

Bleeding is then controlled by applying pressure, using haemostatic agents, electrosurgery or stitches, depending on the nature of the wound.

The sample is labelled and placed in the appropriate container for the requested test. Some techniques, such as immunofluorescence or certain cultures, require a separate sample and specific storage conditions.

What you may feel during and after a skin biopsy

You will usually feel a prick and a brief stinging sensation whilst the anaesthetic is being administered. Whilst the sample is being taken, you may feel pressure, tugging or movement. If you experience any pain, please let the staff know so they can check the anaesthetic before continuing.

Once the anaesthetic wears off, you may experience tenderness, tightness, mild to moderate pain and a small bruise. The severity depends on the size and depth of the biopsy, its location and how your skin heals.

The duration depends on the technique used, the number of samples taken and the type of closure. Small biopsies are usually carried out on an outpatient basis and generally allow you to return home afterwards.

How to look after the wound after a skin biopsy

After the procedure, the wound is covered with a dressing. If stitches have been applied, the medical team will advise when they need to be checked or removed. The specialist’s instructions take precedence, as not all wounds require the same care.

For many biopsies, it is recommended that you gently clean the area, pat it dry without rubbing, apply the prescribed product and keep it protected with a clean dressing. You should not apply alcohol, hydrogen peroxide, iodine or other products unless specifically instructed to do so, as these may irritate the tissue.

The medical team will also explain when you can have a shower, when you can submerge the area, and which movements or exercises you should avoid. Wounds near a joint or subject to strain may require additional precautions.

How a skin biopsy is analysed

The sample is processed in the pathology department and examined under a microscope. Standard staining allows the architecture of the skin and the characteristics of its cells to be studied. Depending on the condition being investigated, additional sections, special stains, immunohistochemistry, immunofluorescence, cultures or molecular techniques may be used.

The pathologist needs to know the location, duration of the condition, the appearance of the lesion, the diagnoses being considered and any previous treatments. This correlation between clinical information and microscopic findings is particularly important in conditions that may share similar histological patterns.

The time taken to receive the results depends on the laboratory and whether further investigations are required. The centre must specify how and when the report will be communicated.

How to interpret the results of a skin biopsy

A biopsy report does not always provide a simple ‘positive’ or ‘negative’ result.

Definite diagnosis

In some cases, the microscopic findings allow a specific diagnosis to be made. If a lesion has been removed, the report may also indicate whether it extends to the edges of the sample. This information helps to determine whether the procedure carried out is sufficient or whether further treatment is required.

Compatible or suggestive result

On other occasions, the tissue shows a pattern that can be seen in several different conditions. The report may suggest various possibilities, which must be considered in conjunction with the skin examination, symptoms, laboratory tests, medication or the patient’s clinical course.

Insufficient or unrepresentative sample

A sample may be too small, too superficial, or taken from an area that does not contain the characteristic changes of the condition. The tissue may also be altered by scraping, ulceration, scarring or previous treatments.

In such cases, it may be necessary to carry out further investigations, review the slides, seek a second opinion or take another biopsy. If the report does not tally with the clinical presentation or the progression of the lesion, the correlation between dermatology and pathological anatomy should be reviewed before finalising the diagnosis.

Limitations of skin biopsy

A biopsy examines a specific sample and does not always represent the entire lesion or all the affected areas. Its accuracy may be reduced if the sample taken is too superficial, an unrepresentative area is selected, or the disease is at a stage where its most characteristic changes are not yet apparent.

Previous treatments, scratching, ulceration and scarring can also alter the tissue.

Furthermore, different conditions may share similar microscopic patterns. In complex cases, it may be helpful to seek the opinion of a dermatopathologist – a pathologist with specialist experience in skin diseases.

Risks and possible complications of a skin biopsy

As the biopsy involves piercing the skin, it may leave a scar or cause a permanent change in colour or texture. It is common to experience tenderness, tightness, minor bleeding or a bruise during the first few days.

Persistent bleeding, bruising, infection, the wound opening up or reactions to the dressing, the antiseptic or any of the products used may also occur. In some people, the scar may become thickened or form a keloid. Depending on the depth and location, there may also be a temporary change in sensation.

The risk depends on the technique used, the size and depth of the sample, the area biopsied, blood circulation, previous treatments and any pre-existing conditions.

When to seek advice following a skin biopsy

You should contact the clinic if you experience:

• Bleeding that does not stop with firm, continuous pressure.

• Pain that gets worse rather than better.

• Redness that spreads, warmth, pus or a fever.

• The wound has opened up.

• A severe reaction to the dressing or the product used.

• A new or noticeable change in sensation.

If there is bleeding, pressure must be applied continuously and you should avoid repeatedly lifting the dressing to check the wound.

Can a skin biopsy also serve as a treatment?

In the case of some small lesions, a shave, punch or excisional biopsy can remove all the visible tissue. In certain cases, this may be sufficient. In others, the pathological report may indicate that it is necessary to widen the margins, carry out another procedure or arrange specific follow-up.

For this reason, completely removing a visible lesion does not automatically mean that treatment is complete.

Skin biopsy, dermatoscopy and other skin tests

Dermatoscopy allows structures within a lesion that are not always visible to the naked eye to be observed under magnification, but it does not obtain any tissue. Scrapings, cultures, laboratory tests or clinical follow-up can answer some questions without the need for a biopsy.

When it is necessary to directly examine the architecture and cellular characteristics of the tissue, a biopsy provides information that these techniques cannot provide in the same way.

No single test automatically replaces the others. The choice depends on the lesion and the diagnostic question.

Skin biopsy specialists at Memorial Publio Cordón

At Memorial Publio Cordón Hospital, the diagnostic assessment of skin lesions is primarily carried out by the Department of Dermatology and Venereology, within the Dermo Centre. The General Dermatology Unit deals with inflammatory, infectious and neoplastic conditions of the skin, hair, nails and mucous membranes.

When a lesion requires excision or a more complex surgical procedure, the Dermatological Surgery Unit may be involved; this unit is dedicated to the diagnosis and surgical treatment of complex skin conditions and is headed by Dr Alberto Conde Taboada.

Once the sample has been obtained, the histopathological analysis provides the microscopic information that must be correlated with the selected lesion and the clinical data sent to the laboratory.

In specific situations, other specialities may take skin biopsies as part of the investigation into a particular condition.

Medical information for general guidance

This factsheet aims to help you understand why a skin biopsy may be requested, how a skin sample is taken, what aftercare the wound may require, and how the histopathological examination contributes to the diagnosis.

Memorial Publio Cordón Hospital promotes rigorous, comprehensible and useful medical information, linked to specialist care, research, scientific dissemination and medical progress.

The indication for the biopsy, the technique chosen, the management of medication, post-procedure care and the interpretation of the results must be tailored to the lesion and the clinical situation of each individual. The pathological report must be considered in conjunction with the dermatological examination and clinical progress.