Skin Lesion Excision and Undermining
Source
Surgeon:
Hannu Kuokkanen
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Summary
Focus: Skin lesion removal and wound closure for pathology reporting or functional/aesthetic reasons.
Key elements: Planning, local anesthesia, skin incision, excision, undermining, closure, aftercare, pitfalls, and complications.
Indications and Clinical Context
General
Medical experts: Hannu Kuokkanen (plastic surgeon), Veikko Schepel (plastic surgeon), Tuomas Rauramaa (pathologist)
Name of Procedure: Skin lesion excision and undermining
Goal of Operation
Skin lesion removal and wound closure.
Problem
Skin lesion that needs to be removed to get the pathologist report on a potentially malignant lesion. Or functional/aesthetical reason.
Diagnosis
Other and unspecified skin changes (ICD-10 R23.8)
Short Pathophysiological Description
Skin lesions can be benign or malignant. Treatment of malignant skin lesions is determined according to the pathology report. To receive the pathology report, it is necessary to perform the skin lesion excision. Sometimes benign skin lesions are removed as well, as they may be difficult to differentiate from malignant ones with the naked eye, or because they may be problematic either functionally or aesthetically.
Key Anatomy and Landmarks
Epidermis
Dermis
Subcutis
Fascia level
Routes of the main cutaneous nerves in the area of intervention
Step-by-Step Technique
Planning
If the nature of the skin lesion is not known (benign or malignant), the entire lesion will be removed with a narrow margin (1 to 2 mm) for specimen.
The incision should be aligned with the skin folds. This will facilitate wound closure and help avoid undue tension in the scar.
In the extremities, the incision should be made along the axis of the limb as this makes any additional procedures easier.
The excision area should be marked with a marking pen before local anesthesia as any palpation finding usually disappears on numbing.
Local Anesthesia
Ask for any possible allergies to local anesthetics. Suspect cases are tested at the allergy unit and, if in doubt, the local anesthetic concerned must not be used.
The most commonly used local anesthetic is lidocaine with adrenaline (concentration of either 0.5 or 1%). Use a thin needle (black or blue for the trunk and lower limbs, orange/blue for the face and hand area).
Use the thinnest needle (biggest gauge) possible for injecting the local anesthetic as painlessly as possible into the entire excision area, from several puncture sites if necessary (in a pre-numbed area). Wait long enough, about 5 minutes in areas of thick dermis. Use the needle to test for analgesia. Administer more anesthetic if necessary.
Inform the patient that there may be some sensation of pressure or touch but sharp pain should not occur.
Skin Incision
Using your fingers, stretch the skin in all directions.
Make the incision with a surgical knife perpendicular to the skin, along the marked lines, all the way through the skin down to the fatty layer (subcutis).
Excision of the Skin Lesion
Excise the tissue including some subcutaneous fat. In an area of thinner skin, the excision can be made down to the fascia level, but in an excision biopsy, this is not necessary.
If necessary, for the purpose of orientation, place marking sutures into the excised tissue specimen (e.g. short suture for superior border and a long suture for posterior border). Suture marking enables any additional excision to be made in the correct direction. You may also photograph the lesion once marked.
Pathologist’s point of view: The absence of suture marking (of orientation) can be a problem. It is useful in any slightly larger specimens, such as a typical basal cell carcinoma. The resected specimen (a 3D object) is made into a 2D microscope slide, making the suture marking important. On arrival at the lab, the specimen is photographed (or drawn in some cases) and then colored. For example, according to suture markings the lateral edge could be colored blue and contralateral edge in some other color. The base of the specimen is also often color stained. The color seen under the microscope will then tell the pathologist the orientation of the edges.
The absence of suture marking is not a problem if the entire lesion has been obtained. However, it is a problem if, for example, an infiltrating basal cell carcinoma reaches the edge of the specimen on the microscope slide and an additional excision proves to be necessary. Without orientation markings, it is impossible to say whether there is residual lesion cranially or caudally.
Undermining
A primary closure is usually possible if the wound sides can be easily made to meet by hand.
If subcutaneous fat protrudes while closing, excess fat can be removed.
Undermining of the wound edges is done at the fascia level or at more superficial level in the subcutis, if the subcutis is thick.
Initial undermining of the skin can be done with a scalpel, if necessary, but the dissection then continues in a blunt manner, with closed scissors, for example. Introduce the closed scissors at the fascia surface and open.
Closure
For wounds in a location of tight skin, use interrupted sutures to make the skin edges meet easier (versus intracutaneous sutures, for example). The choice of suture thickness is determined by the wound location. For the sole of the foot, a 3-0 suture should be used. The table shows guideline suture thicknesses for other skin areas.
It is advisable at first to make a test knot in the center of the wound to see whether the wound edges can be clearly brought together. If the skin edges do not come together, or if there is too much tension and the skin edge becomes pale, some undermining of the skin is necessary.
Only the necessary number of stitches should be applied to achieve closure. Some residual bleeding between the stitches should be allowed.
The knots should not be tightened too much, as it may cause ischemia at the wound edges. The edges should just touch each other.
The wound should be covered with non-woven fabric tape, wound dressing and, if necessary, a spiral bandage.
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Piftalls and Complications
Not Sending the Excised Lesion for Pathological Analysis
All surgically removed skin lesions should be sent for pathological analysis.
From the pathologist’s point of view, a good referral to pathologist contains adequate information, while being concise and to the point, at least the following:
History:
Not all conditions or medications need to be reported, only what is relevant to the excised lesion.
A lesion that is mentioned to have developed in just a few weeks provides the pathologist with a lot of information. And if the lesion has been unchanged for 25 years, that should also be mentioned.
Immunosuppression
Anatomical location of the lesion
If the location is close to a tattoo, it is important to mention it, as any pigment appearing in the specimen may be confusing.
Orientation with suture marking.
Removal technique. For example “elliptical excision”.
Macroscopic description: Color, color homogeneity vs. heterogeneity, any ulceration.
Any working diagnoses and differential diagnoses are worth mentioning.
Wrong Direction of the Incision
Plan the direction of incision correctly. An incision aligned with the skin folds facilitates wound closure and enables additional excisions to be made later.
In the extremities, however, the skin incision should be aligned with the axis of the limb, as this makes any additional procedure (such as a re-excision for adequate margins) easier.
Careless Tissue Handling
When removing the skin lesion, handle the tissue carefully. Grasp gently the specimen with forceps where the skin is intact.
On closing the wound, be careful not to close the skin edges with epidermis-against-epidermis as this will impair the wound healing potential. Shifting the knot placement to the side helps to get the edges properly placed.
Excess wound tension may result in infection, pain, wound dehiscence and increased scarring.
Inadequate Hemostasis
Wound hematoma may make the patient prone to infection and slow wound healing or lead to wound dehiscence.
The patient is instructed to contact the unit where the procedure was performed or the ER if the wound bleeding continues at home or a large hematoma (oedema) develops in the area. Bleeding may be persistent, particularly with patients using anticoagulants.
Principles of hemostasis for minor wounds:
Wipe off blood and any hematoma and then compress with gauze for 2 minutes. The gauze may be soaked with local anesthetic that contains adrenalin.
If there is clear bleeding from a minor vessel, cauterize or ligate it with a suture.
If the bleeding comes from the dermis edges, it will usually subside after wound closure followed by a compression dressing, which may be placed on the wound.
Careless Wound Dressing
Wound tape will prevent wound dehiscence and keep the skin edges aligned. The tape also prevents scar formation for up to 6 weeks. Compression dressing should also be kept in mind. It facilitates hemostasis and also eliminates dead space,* immobilizes the wound (alleviates pain) and prevents wound dehiscence.
*Dead space is an empty space created in the tissue after removal of e.g. a lipoma or some other expansive lesion. Dead space can be made smaller with absorbable stitches. Wound tape might not make it smaller but will give extra support to the wound.
Complications
Wound Edge Ischemia
If the skin at the wound edge is very thin (such as in the elderly) and the wound has been overly tightened it may become necrotic. This is prevented by cutting perpendicular to the tissue so that there will be no thin skin flap and by making sure the wound closure is effortless (skin undermining).
Infection
All surgical interventions are associated with a risk of infection. The wound edge and its surroundings are normally slightly red post procedure, but infection should be suspected if erythema extends well into the intact skin area, the wound is very painful, there is suppurative secretion or the patient has systemic symptoms. If the patient has symptoms of infection, the wound should always be inspected and treated accordingly.
Cutaneous Nerve Injury
Numbness around the wound may be due to injury to a cutaneous nerve (tension or severed nerve). A minor area of numbness is not usually a problem, but the severing of a sensory nerve serving a larger area should be assessed by a specialist (hand surgeon or plastic surgeon).
Aftercare
General Guidelines
The wound dressing / spiral bandage placed on top of the tape can be removed at 24 hours after the procedure and the wound can then be rinsed.
The tape can be left in place until the sutures are removed. If the tape comes off, it can be replaced.
The sutures are removed on a case-by-case basis. Based on the wound location, following timeline recommendations are:
After the sutures have been removed, the scar should be covered with wound tape for up to 2-6 weeks to prevent scar formation.
FAQ
When is a narrow margin used for skin lesion excision?
If the nature of the skin lesion is not known, the entire lesion is removed with a narrow margin of 1 to 2 mm for specimen.
How should the incision direction be planned?
The incision should be aligned with the skin folds to facilitate wound closure and help avoid undue tension in the scar. In the extremities, the incision should be made along the axis of the limb because this makes any additional procedures easier.
Why should the excision area be marked before local anesthesia?
The excision area should be marked before local anesthesia because any palpation finding usually disappears on numbing.
What local anesthetic is most commonly used?
The most commonly used local anesthetic is lidocaine with adrenaline, with a concentration of either 0.5 or 1%.
Why are marking sutures placed in the excised specimen?
Marking sutures may be placed for orientation, enabling any additional excision to be made in the correct direction.
When is undermining necessary?
Undermining is necessary if the skin edges do not come together, if there is too much tension, or if the skin edge becomes pale during test closure.
What dressing is used after closure?
The wound should be covered with non-woven fabric tape, wound dressing, and, if necessary, a spiral bandage.
When can the wound dressing or spiral bandage be removed?
The wound dressing or spiral bandage placed on top of the tape can be removed 24 hours after the procedure, and the wound can then be rinsed.
How long can the wound tape remain in place?
The tape can be left in place until the sutures are removed. If the tape comes off, it can be replaced.
What should be done if bleeding continues at home or a large hematoma develops?
The patient is instructed to contact the unit where the procedure was performed or the ER if wound bleeding continues at home or a large hematoma develops.
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