Skin biopsy: how it's performed and what can be detected

A skin biopsy is the targeted removal of a small area of skin for microscopic examination and additional testing. This method can confirm or refute suspected skin tumors, inflammatory dermatoses, vesicular and vasculitic processes, and infections, as well as clarify rare dermatological diagnoses. The simplicity of the procedure is combined with high diagnostic value, provided the site, depth, and method of sampling are properly selected. [1]

The key to the value of a biopsy is its clinical-pathological correlation. The pathologist is fundamentally concerned with the clinical description, duration and distribution of lesions, suspected diagnoses, and the purpose of the examination. Complete accompanying data increases diagnostic accuracy and reduces the risk of repeat procedures. [2]

In everyday practice, three techniques are most commonly used: superficial shaving, circular punch, and fusiform excision. Each produces different specimen depth and architecture and therefore addresses different objectives. Selecting the correct technique before beginning the procedure is critical to answering the clinical question. [3]

For a number of conditions, the choice of biopsy site is as important as the choice of method. For example, in autoimmune blistering diseases, a perilesional biopsy within 1 centimeter of the blister is taken for direct immunofluorescence, while in melanoma, a diagnostic excisional biopsy with a narrow margin is preferred. [4]

When is a skin biopsy indicated?

The first set of indications is suspected tumors: melanoma, basal cell and squamous cell carcinoma, Bowen's disease, and atypical melanocytic nevi. In these cases, the correct staging based on tumor thickness and subsequent management depend on the sampling technique. If melanoma is suspected, a narrow-margin, excisional biopsy is considered the standard. [5]

The second block is inflammatory dermatoses and rashes of unclear origin. A punch biopsy with a diameter of 3-4 millimeters from a typical fresh lesion provides sufficient depth for assessing the epidermis, dermis, and subcutaneous tissue in papular, nodular, and vasculitic lesions. For widespread rashes, sampling from multiple sites with varying ages is often required. [6]

The third section examines bullous diseases. For direct immunofluorescence, perilesional, apparently intact skin adjacent to the blister is sampled, avoiding the blister floor, where immune complexes may have already been destroyed. For routine histology, the second sample is placed in a fixative. This separation increases diagnostic sensitivity. [7]

The fourth section examines hair and scalp diseases. It's optimal to take two 4-millimeter punch biopsies: one with horizontal sections and the other with vertical sections, to assess both the follicles and the epidermal-dermal junction. The choice of area depends on the type of alopecia. [8]

What methods are there and how to choose them

Superficial shaving is appropriate for superficial lesions and hyperkeratotic lesions where an assessment of the epidermal and upper dermal architecture is needed and depth is not required. If melanoma is suspected, this method should not be used due to the risk of "crossing" the tumor and inaccurate thickness assessment. [9]

A circular punch creates a tissue column throughout the entire thickness of the dermis, often extending into the subcutaneous fat. This is the method of choice for inflammatory dermatoses, vasculitis, nodules, and multiple eruptions. A diameter of 3-4 millimeters is usually sufficient, and in areas with thick dermis, 5-6 millimeters can be used. [10]

An excisional biopsy is used when complete removal of a small lesion with control margins is required, or when architectural continuity is needed to accurately assess margins, as in suspected melanoma or keratoacanthoma. The margin is kept minimal to avoid distorting subsequent treatment planning. [11]

Incisional biopsy is indicated for large or critically located lesions, when complete excision is impossible at the initial stage, as well as for deep infiltrates, where the entire thickness of the dermis down to the subcutaneous tissue must be captured. The incision pattern is chosen based on the lines of least skin tension. [12]

Table 1. Biopsy methods and their strengths

Method	Depth	Typical indications	Restrictions
Shaving	Epidermis and upper dermis	Superficial lesions, seborrheic keratosis, superficial basal cell carcinomas	Not suitable if melanoma is suspected
Punch	The entire dermis, sometimes subcutaneous tissue	Inflammatory dermatoses, vasculitis, nodules, alopecia	Small diameter may limit edge evaluation
Excision	Full thickness with edges	Suspected melanoma, keratoacanthoma, cases where continuous architecture is needed	Requires stitches and careful planning
Incision	Sector for the entire thickness	Large foci, deep infiltrates	Does not remove the lesion completely

Source: summary of current guidelines and reviews. [13]

Preparation, pain relief and safety

Before the procedure, the sampling site is marked with a marker, as after anesthetic infiltration, the skin blanch and landmarks are lost. The skin is treated with an antiseptic, and the infiltration volume is chosen to be minimal, sufficient for painless manipulation, so as not to distort the microscopic image. [14]

The most commonly used lidocaine is one percent or one percent lidocaine with adrenaline at a concentration of one part in one hundred thousand. The maximum safe doses for infiltration anesthesia in adults are: without adrenaline up to 4.5 mg per kg of body weight, with adrenaline up to 7 mg per kg, with the total dose usually not exceeding 500 mg. For children, the doses are lower and calculated individually. [15]

Current data confirm the safety of adrenaline for finger blocks and other extremity blocks in patients without critical circulatory disorders, thus challenging the old prohibition. It reduces bleeding and prolongs the anesthetic's effect, but the decision is made individually, taking into account the vascular status. [16]

Antibiotic prophylaxis for uncomplicated skin procedures, including routine biopsies, is generally not required. Routine application of topical antibiotics to clean wounds offers no advantage over petroleum jelly and increases the risk of contact dermatitis; exceptions include special risk groups and specific surgeries. [17]

Table 2. Local anesthetics: guidelines for practice

Substance	Concentration of example	Maximum for adults without adrenaline	Maximum in adults with adrenaline	Comments
Lidocaine	1 percent	up to 4.5 mg per kg	up to 7 mg per kg, in total up to 500 mg	Standard in dermatosurgery
Pramocaine, prilocaine and others	It varies	depend on the drug	depend on the drug	Please check the official instructions.
Tumescent infiltration	diluted solution	special modes	special modes	Used for major interventions

Summary and regulatory data. [18]

Choosing a Fence Location and Depth: Practical Scenarios

If melanoma is suspected, a narrow-segment excisional biopsy is chosen to assess tumor thickness and levels of invasion as accurately as possible. Partial superficial biopsy is avoided as it may understate the stage. [19]

For bullous diseases, two samples are taken: one from perilesional, apparently normal skin for direct immunofluorescence, and the second from the edge of the blister or fresh erosion for standard histology. This approach increases sensitivity and specificity. [20]

For alopecia, it's optimal to perform two 4-millimeter punch biopsies to a depth of subcutaneous tissue. One is used for horizontal sections to count follicles, the other for vertical sections to assess the epidermal-dermal junction and interface changes. The location is selected based on the type of alopecia. [21]

If vasculitis is suspected, it is important to collect a sample from fresh, palpable purpura up to 24-48 hours old, deep into the dermis and subcutaneous tissue, to detect early fibrinoid changes and vascular inflammation. For nodules and infiltrates, aim for the center of the dense lesion, avoiding necrotic crusts. [22]

Table 3. Where and how to take a biopsy for different purposes

Clinical task	Fence location	Preferred method	Additionally
Suspicion of melanoma	The entire thickness of the hearth	Narrow margin excision	Avoid superficial shaving
Bullous diseases	Perilesional skin and margin of the blister	Two samples: for immunofluorescence and for histology	Do not use formalin for immunofluorescence.
Alopecia	Active zone or edge of the lesion	Two 4 mm punch biopsies	Horizontal and vertical cuts
Vasculitis	Fresh palpable purpura	Punch of sufficient depth	It is important to capture the subcutaneous tissue

Sources: clinical guidelines and reviews. [23]

How to direct and transport material

For routine histology, the specimen is immediately placed in 10% neutral-buffered formalin. The volume of the fixative should be at least ten times the tissue volume. The jar is labeled with full patient identification, the exact anatomical site, and the date. [24]

Formaldehyde is not suitable for direct immunofluorescence. A special Michel transport medium is used, or fresh tissue is delivered urgently in saline, depending on the laboratory's capabilities. Preservation of antigens in Michel transport medium has been shown to extend the delivery window. [25]

If microbiology is required, for example, if atypical mycobacteria, fungal infections, or deep bacterial lesions are suspected, a portion of the tissue is sent fresh in a sterile container with gauze moistened with saline. Formaldehyde is not acceptable for culture. [26]

Preliminary consultation with a pathologist increases the value of the examination: the need for additional stains, cultures, and marginal markers can be discussed in advance. This reduces the likelihood of re-intervention. [27]

Table 4. Transport environments and purposes

Purpose of the study	What to send	Environment and conditions
Routine histology	Solid sample	Ten percent neutral formalin, at least ten times the volume
Direct immunofluorescence	Perilesional skin	Michel's Wednesday or fresh fabric with express delivery
Microbiology and polymerase chain reaction	Fresh fabric	Sterile container, gauze moistened with saline solution, without formalin

Sources and laboratory memos. [28]

Postoperative care and suture removal

The basic principles are simple: clean, moist, and covered. The wound is washed with mild soap and water after the first 24-48 hours, as directed by the doctor, gently dried, and a thin layer of petroleum jelly applied, then covered with a bandage. Topical antibiotics are generally unnecessary and increase the risk of allergic dermatitis. [29]

The time it takes to remove sutures depends on the location and tension of the skin: the face usually takes 5-7 days, the scalp 7-10 days, the torso and limbs 10-14 days, and over joints up to 14-21 days. Removing sutures too early increases the risk of divergence, while removing them too late increases the risk of suture marks. [30]

The patient receives clear instructions on monitoring for signs of infection and bleeding, as well as protecting the scar from ultraviolet light to minimize pigment changes. When shaving, where an open erosion is left, moist-protective dressings are used until complete epithelialization. [31]

Simple but important measures to stop capillary bleeding include pressure, aluminum chloride, and, if necessary, coagulation. In areas with significant blood flow, the decision to apply pressure dressings and temporarily limit stress is made on an individual basis. [32]

Table 5. Guidelines for suture removal times

Location	Estimated timeframe
Face	5-7 days
The scalp	7-10 days
Torso	10-14 days
Arms and legs	10-14 days
Above the joints, palms, feet	12-21 days

Summary of manuals and textbooks. [33]

Antithrombotic Therapy and Bleeding: What's Important to Consider

For most patients taking warfarin, antiplatelet agents, and direct oral anticoagulants, discontinuing the drug before minor skin surgery is unnecessary and may be riskier due to the risk of thromboembolism. For warfarin, an international normalized ratio (INR) of less than 3.5 is recommended, and expanded recommendations for pressure dressings are given. [34]

Current UK guidelines for dermatological surgery recommend continuing aspirin, and for direct oral anticoagulants the decision should be made taking into account the balance of risk of bleeding and thrombosis, the type of intervention and associated factors; sometimes skipping one dose is sufficient. [35]

Systematic reviews and clinical guidelines for outpatient dermatology concur: for minor procedures, continued anticoagulants and antiplatelet agents are generally safe with proper hemostatic technique and patient education. Exceptions include combinations of drugs and procedures with high wound burden. [36]

If individual risk factors are present, such as uncontrolled hypertension or recent cardiac surgery, the plan is coordinated with the attending physician and laboratory. Dose and schedule adjustments are made only in consultation with the prescribing specialist. [37]

Table 6. Antithrombotics and minor dermatological surgery

Preparation	Basic recommendation for minor skin procedures	Note
Aspirin	Continue	Discontinuation is possible when taking only for prevention, by agreement
Clopidogrel	Continue more often	For combinations and complex wounds - an individual solution
Warfarin	Do not cancel if the international normalized ratio is below 3.5	Checking the indicator and strengthening local hemostasis
Direct oral anticoagulants	Individually, most often they don't cancel	It is possible to skip one dose if the risk of thrombosis is low.

Summary of official documents. [38]

Complications and how to prevent them

The most common adverse events are bleeding, hematoma, infection, wound dehiscence, hypertrophic scarring and keloid, and allergic contact dermatitis to topical antibiotics or patches. The infection rate with clean technique is extremely low and rarely exceeds one percent. [39]

Prevention includes adequate hemostasis, sparing tissue trauma, proper selection of suture material, and timely removal of sutures. Vaseline is preferred over antibiotic ointment for care, as the benefits of the latter are minimal and the risk of allergy is significantly higher. [40]

Post-procedure pain is usually moderate and can be controlled with paracetamol. Nonsteroidal anti-inflammatory drugs (NSAIDs) may slightly increase bleeding, so their use is discussed on an individual basis. If infection or increasing bleeding is suspected, the patient is given a clear plan of action and a contact information for an unscheduled follow-up appointment. [41]

Particular attention is paid to areas at risk of keloids, such as the sternum and shoulder girdle: here, alternative techniques, more gentle incisions, and prevention of hypertrophic scars are discussed in advance. [42]

Table 7. Frequent complications and prevention

Complication	How to reduce the risk
Bleeding and hematoma	Adrenaline in anesthetic, pressure, coagulation, pressure bandage
Infection	Clean technique, clean-wet-closed care, without routine topical antibiotics
Wound dehiscence	Adequate deep support with threads, consideration of tension lines, timing of suture removal
Allergic contact dermatitis	Avoid unnecessary topical antibiotics and aggressive antiseptics
Hypertrophic scar and keloid	Gentle incision, early removal of superficial threads, UV protection

Summary of data and recommendations. [43]

Common mistakes and how to avoid them

Mistake number one is choosing the wrong method. Shaving a superficial biopsy when melanoma is suspected can lead to an incorrect assessment of thickness and staging. The correct course of action is a diagnostic, narrow-margin, excisional biopsy. [44]

Mistake two: sampling from the wrong area. In bullous diseases, sampling from the bottom of the blister reduces the sensitivity of direct immunofluorescence; perilesional skin is used. In alopecia, the choice of site depends on the type: for cicatricial alopecia, the active edge; for non-cicatricial alopecia, the most affected area. [45]

Mistake number three is improper transportation. Specimens for direct immunofluorescence and microbiology should not be placed in formalin. Appropriate media and prompt logistics should be used. [46]

Mistake number four is the unjustified discontinuation of anticoagulants and antiplatelet agents. For minor skin procedures, this often increases risks rather than reduces them. Decisions are made according to approved regimens and in coordination with the prescribing physician. [47]

Table 8. "Catch the mistake": a wrong step and the right alternative

Wrong step	What to replace it with
Shaving off a plaque suspicious for melanoma	Diagnostic excisional biopsy
Bladder fundus biopsy for immunofluorescence	Perilesional skin near the blister
Place everything in formalin "just in case"	For immunofluorescence - Michel's medium; for microbiology - a sterile container
Discontinue warfarin before punch biopsy	Continue with international normalized ratio below 3.5 and enhance hemostasis

Sources: clinical guidelines. [48]

Mini-protocol

Step 1. Formulate the clinical question and select the method, location, and depth based on the diagnosis. Mark the area with a marker before infiltration. [49]

Step 2: Administer infiltration anesthesia, taking into account safe doses and possible use of adrenaline to reduce bleeding. [50]

Step 3. Perform the collection with minimal tissue trauma, ensure hemostasis by pressure, aluminum chloride solutions and, if necessary, coagulation. [51]

Step 4. Immediately place the samples in the correct environment, label the jars correctly and issue referrals with clinical information and a question for the pathologist. [52]

Step 5: Provide the patient with written instructions for care and follow-up times, including signs requiring an unscheduled visit and guidelines for suture removal. [53]

Questions and Answers

Question: Are antibiotics needed for a wound after a skin biopsy?
Generally, no: Vaseline is equally effective at preventing infection and is less likely to cause contact dermatitis. Antibiotic use is considered on a case-by-case basis. [54]

Question: Is adrenaline used in finger anesthetics dangerous?
With normal blood flow, adrenaline is acceptable and aids hemostasis, as confirmed by studies and reviews. [55]

Question: When should stitches be removed?
Guidelines: face 5-7 days, scalp 7-10 days, trunk and limbs 10-14 days, over joints and on soles up to 14-21 days. [56]

Question: What should be done while taking warfarin or aspirin?
In most cases, continue and focus on local hemostasis and proper dressing. Decisions about changing therapy are discussed with the prescribing physician. [57]