Skin biopsy consists of obtaining a skin sample with diagnostic tests and at the same time, in some occasions, allows to treat a specific isolated skin injury.
In turn, biopsies can be partial, when we only take a small part of the skin injury, or total when what we perform is a complete extraction of the injury. In most cases, total biopsies are performed for therapeutic purposes in addition to diagnosis, thus eliminating a skin injury completely.
It is one of the most frequent and important procedures performed in a dermatology consultation, since the skin is easily accessible and also because the histological examination of a skin sample provides a lot of information and is one of the tests that offers the most cost-effective performance in our daily practice.
When does a skin biopsy need to be done?
The usual thing is that dermatologists perform a biopsy when we want to find out or confirm a diagnosis in a patient who comes due to the presence of one or various skin injuries. In many occasions, the histopathological examination of the skin sample extracted offers us an exact or very approximate diagnosis of a certain disease and in this way we will be able to propose the most appropriate treatment to the patient.
In the case of skin injuries that are removed due to cosmetic reasons, it is also wise to send the sample for histological evaluation for medical-legal reasons.
However, on certain occasions, patients are referred to us to take biopsies of “normal” or non injured skin in order to contribute to the diagnosis of certain systematic diseases, even in the absence of skin injuries.
Some of the diseases where by the skin biopsy can be of great help for the diagnosis are:
- Systemic Amyloidosis: constitutes a heterogeneous group of diseases characterized by deposits of insoluble extracellular proteins in one (localized amyloidosis). In cases of systemic amyloidosis, partial abdominal fat biopsy can allow an Earl diagnosis and prevent the evolution of the disease.
- Neurophaties: Skin biopsy has proven to be a useful method in the diagnosis of small nerve fiber neuropathies since, by definition, these cannot be diagnosed by normal nerve conduction studies because they only reflect the function of thick myelinated nerve fibers.
- Genetic diseases: Alport syndrome, metabolic diseases (lysosomal pathologies, dystrophinopathies..) among others.
How is this procedure?
The election of this technique and the adequate area of the skin for the biopsy requires to value on one hand, the number of injuries, the quantity of tissue that we need to do a diagnosis and on the other hand minimize the resulting scars.
Sometimes, the aesthetic advantage that a small biopsy can have, may turn out to be insufficient and require a second procedure to be performed with worst cosmetic results than if an adequate biopsy had been done, with more skin, in the first place.
There are 3 main techniques to perform a skin biopsy, either partial or total, and they are:
- By shaving: It is done with a scalpel Blade and is more useful for warty or exophytic injuries that can only affect the epidermis or superficial dermis, such as some nevi, seborrheic keratosis, some thick actinic keratosis…. In these cases the wound is usually kept open.
- By Punch: If the injury is deeper (located in the Deep dermis or hypodermis) this instrument is usually required in order to properly access and take a sample of the injury. After taking a sample the would can usually be left open or sutured with stitches.
- Exeresis with a scalpel blade: It can be superficial or deeper injuries and, in these cases, the wound is left sutured with stitches.
As I have stated previously, in the majority of occasions, skin biopsies are done on the same day the patient comes to the medical visit; however, in those cases where the skin biopsy is programmed on a different day, it is recommended that the patient is accompanied by someone.
What cures should be followed after a skin biopsy?
As we have just seen, the resulting wound after a skin biopsy can be left open or sutured with stitches. We then cover it with a sterile dressing, which sometimes has to be thick and compressive to prevent possible bleeding on the same day.
If the wound is left open, the patient is recommended to remove the dressing and perform normal hygiene the day after the procedure on the area to be treated, applying an antibiotic ointment or a topical antiseptic (eg: iodine or alcohol) daily to disinfect and help dry the wound and scab formation.
The scab will take 2-3 weeks to fall, leaving a more vulnerable area of skin, so it is very important to apply sun protection during days and months after the technique is performed to avoid the development of little cosmetic spots (hyperpigmentation).
If the wound is sutured, it is generally recommended that the patient keep the area covered for a few days and then perform normal wound hygiene and application of and antibiotic ointment until the stitches are removed.
What are the long term or short term complications that can appear?
The most important complications to consider after a skin biopsy, specially is the wound is left open, are the possibility of bleeding, infection and cosmetic spots with hyperpigmentation (white scars) or hyperpigmentation (dark scars).
To avoid the risk of bleeding (which if it occurs, it usually does on the same day), a small compression bandage can be placed on the treated area for 24 hours.
To reduce the risk of the infection, it is recommended that the patient disinfects the wound daily with yodine solution or alcohol and also in some occasions should apply the antibiotic ointment for a week.
To minimize the risk of hyperpigmentation it is recommended that the patient uses a high sun protection for a few months after the technique is performed.
Punch biopsy scheme
- Dirk M Elston , Erik J Stratman , Stanley J Miller. Skin biopsy: Biopsy issues in specific diseases. J Am Acad Dermatol 2016 Jan;74(1):1-16.
- David Veitch, James Miller, Shyamal Raichura, John McKenna. Skin biopsy. Br J Hosp Med (Lond) 2018 May 2;79(5).
- Claudia Sommer. Nerve and skin biopsy in neuropathies. Curr Opin Neurol 2018 Oct;31(5):534-540.
- N Kluger, S Fraitag, A-M Roguedas, L Misery. Normal skin biopsy as a tool for extra-cutaneous disorders. Ann Dermatol Venereol 2014 Mar;141(3):192-200.