Skin Biopsy for Eczema: When is it Necessary?

‍Eczema, or atopic dermatitis, is a common chronic skin condition characterized by dry, itchy, and inflamed skin. It affects 16.5 million US adults and 9.5 million children. Eczema can massively impact a person’s quality of life if not properly managed.

Eczema is primarily a clinical diagnosis based on symptoms like itchy red rashes and skin thickening from chronic scratching. The rash commonly appears in flexural areas (like inner elbows and knees) in older children and adults and on the face in infants. 

While eczema is primarily a clinical diagnosis, occasionally a skin biopsy may be recommended. In this article we’ll cover what a skin biopsy is; when a skin biopsy might be ordered; and what patients can expect.  

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What is a Skin Biopsy?

A skin biopsy is a common diagnostic tool used by dermatologists to examine skin conditions or growths. The process involves removing a small sample of skin for microscopic examination. 

There are various methods for performing a skin biopsy. Each is selected based on the depth and location of the skin lesion.

Shave Biopsy

To perform a shave biopsy, a thin layer of skin is scooped off using a scalpel.

Punch Biopsy

In a punch biopsy, a circular tool is used to remove a deeper, full-thickness skin sample. This can be helpful for assessing several layers of skin, which may be necessary to further assess eczematous rashes.

Excisional Biopsy

The entire lesion is removed using a scalpel in an excisional biopsy. This is often ordered for suspected melanomas, and not typically done for eczema.

When is a Skin Biopsy Necessary for Eczema?

A skin biopsy may be ordered in cases of eczema when the diagnosis is unclear or when symptoms are severe, persistent, or atypical. It helps rule out other conditions that may mimic eczema, such as psoriasis, fungal infections, or skin cancers. 

A biopsy may also be considered when eczema does not respond to standard treatments or to investigate potential secondary infections or unusual eczema presentations that complicate management.

Differentiating Between Eczema and Other Skin Conditions

A skin biopsy is generally ordered in cases of atopic dermatitis (eczema) when the diagnosis is uncertain or when symptoms do not improve with standard treatments. The biopsy can help rule out other skin conditions such as psoriasis, infections, or cutaneous T-cell lymphoma. 

Additionally, a biopsy may be useful when there is suspicion of other associated or underlying conditions exacerbating the eczema. In the context of eczema, the biopsy results often show nonspecific findings such as inflammation, but it is mainly used to confirm or exclude other diagnoses.

Unusual or Atypical Eczema Presentations

In severe, persistent, or unusual eczema cases, symptoms may deviate from typical presentations. In this setting, ruling out an infection, an autoimmune condition like psoriasis or a cancerous condition like cutaneous T cell lymphoma is essential to provide the proper treatment. 

A skin biopsy may be needed to confirm the diagnosis of eczema and rule out another underlying condition.

Persistent or Resistant Eczema

Standard treatments may fail in cases of persistent or resistant eczema. A biopsy can identify secondary conditions, including infections, that may prevent eczema treatments from working effectively. 

Investigating Skin Infections

Eczema can be complicated by secondary bacterial or fungal infections. A biopsy can confirm infections that may require specific treatments, improving eczema management.

However, biopsy is not the first-line method of infection diagnosis. A culture can identify a bacterial infection, and a potassium hydroxide (KOH) preparation can identify a fungal infection. 

What to Expect During a Skin Biopsy for Eczema

A skin biopsy is a straightforward outpatient procedure. 

Preparing for the Skin Biopsy Procedure

Before performing a biopsy, the doctor will review the patient's medical history, including any bleeding disorders or use of anticoagulants. 

The biopsy site is chosen carefully based on the lesion or area that will provide the best diagnostic yield. The site is cleaned with an antiseptic, usually alcohol, to reduce bacterial count and remove oils from the skin. 

For red lesions, the site is marked before injecting local anesthesia because the injection can cause the area to blanch.

The Biopsy Procedure

The biopsy can be performed using different techniques depending on the type of lesion and the amount of tissue needed. 

For a shave biopsy, a scalpel or blade is used to shave a thin layer of skin, mainly for superficial lesions. The skin is stretched or squeezed to help the procedure.

For a punch biopsy, a cylindrical blade is used to remove a full-thickness section of skin. Punch biopsies are useful for diagnosing inflammatory skin conditions. The skin is stretched, and the punch is rotated into the skin to obtain a tissue sample. Small punch sites may be closed with sutures.

The entire lesion is removed during an excisional biopsy, often used for suspected melanomas or small lesions. It may involve full-thickness removal of skin, sometimes including subcutaneous tissue.

During the biopsy, hemostasis (control of bleeding) is usually achieved with chemical agents or sutures. After the procedure, the wound is cleaned, covered with a sterile ointment (usually petroleum jelly), and a non-stick dressing is applied.

Recovery and Aftercare

The biopsy site typically heals over a few weeks. Shave biopsies may leave a crusted area that heals with mild pain and some degree of scarring (either hypopigmented or hyperpigmented). Punch and excisional biopsies may require sutures, and absorbable sutures can eliminate the need for removal. 

While healing, the biopsy area should be kept clean and dry. Dermatologists usually recommend against using topical antibiotics, as the risk of infection is lower than the risk of an allergic response to the antibiotic cream.

Infection rates are low, but prophylactic antibiotics may be considered for high-risk patients. 

Patients should be informed that some degree of scarring is expected at the biopsy site.

A skin biopsy is generally a low-risk procedure. However, if bleeding persists longer than 20 minutes contact your dermatologist, especially if you take blood thinners. Also contact your dermatologist if pain worsens or if signs of infection like increased swelling, warmth, pus, or fever develop. 

Understanding Biopsy Results

Biopsy samples are analyzed in a laboratory by pathologists.

Biopsy Sample Analysis

Biopsy samples are often examined underneath a microscope. They may also undergo special preparation such as special staining procedures, electron microscopy or flow cytometry to examine cellular details, or immunohistochemistry or gene testing to identify inflammatory or cancerous patterns. 

What Biopsy Results Can Reveal

A skin biopsy can help differentiate eczema from other dermatologic conditions like contact dermatitis, fungal infections, or more serious skin diseases.

When a skin biopsy shows eczema, it usually shows general findings like thickened skin (epidermal hyperplasia), swelling between skin cells (spongiosis), and inflammation in acute eczema. 

However, in chronic eczema the skin tends to thicken even more (hyperplasia and hyperkeratosis) and the inflammation continues, but without the swelling seen in the early stages.

A biopsy may also reveal findings indicative of signs of infection, abnormal cell growth or the presence of cancerous cells, or inflammatory skin changes.

Timeframe for Receiving Results

It’s important to discuss the timeframe for receiving biopsy results with your doctor, as some results may be available in a few days while others can take up to a few months, depending on the interpretation requirements and the lab’s procedures.

How a Skin Biopsy Influences Eczema Treatment

The results of a skin biopsy may provide necessary information that leads to an adjustment in treatment plans to address the newly discovered cause. 

Shifting treatment from eczema to another condition: a skin biopsy may reveal that the suspected eczema is actually another condition like a fungal infection, psoriasis, or cutaneous lymphoma, prompting a shift in treatment focus.

Adding or changing medications: if a biopsy detects an infection, treatment may be adjusted to include antifungals or antibiotics that target the underlying issue more effectively.

Guiding more aggressive treatment: a biopsy showing severe inflammation or immune disorders may lead to stronger treatments, like systemic corticosteroids or immunosuppressants, to better manage the condition.

Risks and Considerations of a Skin Biopsy

• Potential complications: scarring, infection, delayed healing.
• Weighing the benefits of a biopsy when the diagnosis is uncertain.
• Importance of discussing concerns and potential outcomes with your dermatologist.

While a skin biopsy is generally a safe procedure, it does come with certain risks. It is important to talk with your dermatologist about these potential risks before proceeding with the biopsy.

Potential Complications

The potential risks of a skin biopsy include bleeding and hematoma formation; infection is another potential risk, although it occurs in less than 5% of uncontaminated procedures. 

Pressure dressings and ice can help manage bleeding and minimize hematoma development, while prophylactic antibiotics may be given to high-risk patients to prevent infection. 

Delayed healing is another possibility, and in rare cases, patients may experience hypersensitivity reactions or a vasovagal response (fainting). If fainting occurs, the patient can be treated by elevating the legs or using the Trendelenburg position. 

Weighing the Benefits

When the diagnosis is uncertain, a biopsy can provide necessary diagnostic information.

It's important to talk with your dermatologist about any concerns or potential outcomes, including what the biopsy will reveal and how it may impact treatment plans, for informed decision-making before proceeding with the procedure.

When to Discuss a Skin Biopsy with Your Doctor

Sometimes, patients struggle with eczema flare ups that feel uncontrollable. If you’ve been working with a doctor and haven’t found relief, it may be time to discuss a skin biopsy with your doctor.

Signs That Indicate a Biopsy May Be Necessary

If you have symptoms that are unusual for your condition, such as rapidly changing, growing, or non-healing lesions, or if your skin condition does not improve with standard treatments, it may be time to consider a biopsy to rule out more serious conditions like skin cancer or infections.

How to Approach the Conversation With Your Dermatologist 

When discussing a biopsy with your dermatologist, express your concerns clearly and ask about the benefits, risks, and alternatives to the procedure. It’s important to understand why a biopsy may be recommended and how it might help in diagnosing or adjusting your treatment plan.

When a Second Opinion or Referral to a Specialist Might Be Helpful

If you feel unsure about the need for a biopsy or if your diagnosis remains unclear after initial tests, seeking a second opinion or a referral to a dermatologist who specializes in skin conditions or biopsies could provide additional insight and reassurance.

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Key Takeaways

• Skin biopsies are useful for diagnosing complex or atypical eczema when symptoms are unclear, severe, or resistant to treatment. They can help rule out other conditions such as infections, psoriasis, or skin cancers, guiding more effective treatment plans.

• Trust your dermatologist’s judgment in recommending a biopsy if necessary. Dermatologists carefully consider the benefits of biopsies when diagnosis is uncertain or standard treatments are ineffective.

• Though a minor procedure, a biopsy may provide necessary information that improves treatment options. It helps identify underlying issues, leading to more tailored and effective eczema management.