Nail biopsy is a procedure that is not often used, but when indicated it is often the only remaining clue to diagnosis.
The goal of nail biopsy is to achieve an accurate diagnosis of nail pathology through a simple and safe surgical procedure.
Although our knowledge in the field of diagnostic imaging (such as nail dermoscopy or onicoscopy) is advancing rapidly, it is still in the intial stages, mainly due to the lack of controlled studies that establish the sensitivity or specifity of the criterio for diagnosis of nail diseases (onicoscopic).
This further underscores the importance of the hispathological study by biopsy of the nail unit, which today remains the ”gold standard” for diagnosing many nail injuries.
When is a nail biopsy performed?
Special care must be taken with diabetic patients, those with peripheral vascular disease, arterial insufficiency, etc, which can compromise digital vascularization and, therefore, healing after the surgery.
The patient should also be aware than even a biopsy may not be able to confirm the diagnosis in all cases since the small size of the sample collected can sometimes compromise the histopathological interpretation.
It is a useful technique especially when we are dealing with isolated nail injuries, since it offers a definitive approach to the treatment. These are usually patients who do not have typical skin injuries from which a diagnosis could be made more easily.
In general, there are two large groups of nail biopsies; nail bed biopsies and nail matrix biopsies:
- The biopsy of the nail bed (which is located below the nail plate or nail itself) is usually required for those situations of a) a “rupture” of the nail at the distal level (onycholysis), b) the accumulation of tissue underneath of the nail (or subungual hyperkeratosis) or c) in the presence of any tumor growth of the nail bed.
- The nail matrix biopsy will be performed where there are changes in the nail plate, since there occur as a result of the existence of alterations at the level of the nail matrix itself: therefore, the histopathologic features of disorders such as melanonychia and erithronychia are good examples to perform a nail matrix biopsy.
The scenenarios in which it is especially beneficial (and sometimes necessary) to perform a nail biopsy would be the following:
- Melanonychia: These are Brown or blackish longitudinal bands, of variable amplitude at the level of the nail and originating in the nail matrix; When it is suspected that this melanonychia may be the expression of a underlying malignant injury, it is necessary to perform a biopsy at the level of the nail matrix.
- Erythronychia: Is a linear red band on the nail plate that originates in the proximal nail fold and can be caused by benign, malignant, or other systemic diseases.
- Isolated nail alterations (dystrophies): these are alterations in the morphology and structure of the nail that are generally due to inflammatory causes and originate in the nail matrix.
- Tumors del llit ungueal: Many times the imaging tests performed (for example and MRI) in order to define if there is a tumor below the nail are not conclusive, so we have to resort to a biopsy to clarify the diagnosis.
- Tumors originating in the nail matrix: such as onychomomatricoma, onycopapilloma, onycopapilloma or glomus tumor, where the biopsy can be both diagnostic and therapeutic.
- Onychomycosis: Sometimes, when the culture for fungi is negative but there is still a high clinical suspicion of fungal infection, we have to resort to a biopsy of the tissue below the nail in order to confirm the diagnosis and be able to administer an appropriate treatment.
Special care must be taken with diabetic patients, those with peripheral vascular disease, arterial insufficiency, etc., which can compromise digital vascularization and, therefore, healing after surgery.
The patient should also be aware that even a biopsy may not be able to confirm the diagnosis in all cases since the small size of the sample collected can sometimes compromise the histopathological interpretation.
How is a nail biopsy performed?
It is a simple procedure (although it requires some training) that is performed in the operating room on an outpatient basis under local anesthesia. Effective local anesthesia is essential as the nail unit is a very sensitive structure with a large number of free nerve endings.
To perform the nail bed biopsy, the partial or total removal of the distal nail is required to delimit the area where the sample will be taken.
For the nail matrix biopsy, the partial removal of the proximal nail is required to locate the specific area to take the biopsy.
What complications can appear postoperatively in the short and long term?
The complications to take into account in the immediate postoperative period are bleeding and infection, however if the technique has been performed under aseptic conditions and an adequate compression bandage is applied, these complications do not usually occur.
The postoperative pain is proportional to the extent of the nail plate extraction, and may depend on inherent characteristics of the patient. In general, it is usually mild-moderate in nature and can be managed well with common pain relievers.
Depending on the location of the biopsy, the patient also has to be prepared for a possible interruption of normal activities (such as writing, driving, etc.) until the biopsy site partially or completely heals.
When a toenail is operated, the need to wear loose-fitting footwear should be noted to accommodate the compression dressing, which is usually bulky in the first few days.
The patient must also be informed regarding the possibility of the appearance of a dystrophy or permanent nail alteration (both in matrix and nail bed biopsies), as well as the possibility of not achieving a definitive diagnosis with the procedure.
Final summary: nail biopsy is a relatively simple procedure that must be performed in selected cases in order to reach a diagnosis of a certain nail alteration. Postoperative complications are rare but can cause permanent alteration of the nail after the procedure.
- Chander Grover, Uma K Chaturvedi, Belum Siva Nagi Reddy. Role of nail biopsy as a diagnostic tool. Indian J Dermatol Venereol Leprol May-Jun 2012;78(3):290-8.
- Eckart Haneke. Anatomy of the nail unit and the nail biopsy. Semin Cutan Med Surg 2015 Jun;34(2):95-100.
- P Rich. Nail biopsy. Indications and methods. J Dermatol Surg Oncol 1992 Aug;18(8):673-82.