Definition and Overview
A biopsy of nail unit is performed to help diagnose nail disorders or to examine a suspected cyst, wart, or tumour. It involves taking a small piece of tissue from any of the many different components of the nail, such as the nail plate, nail bed, hyponychium, proximal nail fold, or the lateral nail fold. The results of the biopsy are used to determine the most appropriate treatment plan for the condition.
Who Should Undergo and Expected Results
The procedure is for patients who are suspected of having a nail disorder due to the presence of some symptoms, such as:
- Recurrent fungal nail infections
- Nail plate deformity
- Longitudinal pigmented streaks on the nail surface
A biopsy can help diagnose the following problems:
- Malignant periungual and subungual tumours
- Benign tumours
- Psoriatic nail
- Mycotic nail
- Lichen planus
Although it is not considered as the primary diagnostic tool for nail disorders, the procedure is sometimes necessary when the results of routine diagnostic procedures are inconclusive.
How is the Procedure Performed?
There are many types of nail biopsy depending on which part of the nail is involved. Determining the most effective and most appropriate biopsy method to use is important to ensure that the procedure is both safe and beneficial for the patient. Local anaesthesia is typically used especially if the procedure is expected to be invasive. The anaesthetics are applied through an injection or a digital block, in which the anaesthesia is injected through the web spaces along the side of the toe or finger.
The different types of biopsies performed on the various components of the nail include:
Nail plate biopsy – This procedure is typically performed to diagnose mycotic nail dystrophies. It involves taking a piece of the distal plate and a portion of the hyponychium underneath it using scissors or a scalpel. If the disease is suspected to have spread beyond the distal nail plate, a trephine punch may be used to gain access to the periosteum. The punch, which is usually 3 to 4 mm in size, is then withdrawn along with the tissue sample.
Nail bed biopsy – This is commonly performed to confirm a suspected tumour or lesion in the nail bed. It is carried out through a standard punch biopsy, which leaves only a small wound that does not require sutures. In some cases, a nail bed sample is taken along with a nail plate sample in a procedure called a 2-punch technique. In most cases, patients heal well and experience minimal scarring following the procedure.
Nail matrix biopsy – This is performed to diagnose tumours that form on the nail matrix or to determine the cause of nail malformations and dystrophies. It is also helpful in diagnosing melanonychia striata or malignancy. The procedure can be performed by removing the whole lesion using a 3mm punch biopsy or through a transverse elliptical wedge excision.
If the tissue taken is bigger than 2 mm, the wound is closed with sutures. The tissue sample is then placed in a periodic acid-Schiff or Gomori methenamine-silver stain.
Possible Risks and Complications
A biopsy of the nail unit is associated with some complications, such as:
- Incomplete tumour removal
- Splitting of the nail
To help minimise complications, only the smallest amount of tissue possible is taken during a nail biopsy to reduce the risk of affecting the surrounding healthy tissue. The larger the punch biopsy used, the greater the risk of complications. Most doctors also prefer to perform a biopsy of the nail bed to avoid affecting the nail matrix.
The above complications can be avoided or minimised by taking only longitudinal samples of the nail bed, most preferably at the lateral margin of the nail, and transverse samples of the nail matrix.
Rosendahl C. “Nail matrix biopsy.” 2013. DermNet New Zealand. http://www.dermnetnz.org/topics/nail-matrix-biopsy/
Rich P, Jefferson JA. “Nail biopsy: Indications and techniques.” http://www.uptodate.com/contents/nail-biopsy-indications-and-techniques
Onumah N. “Nail surgery workup.” http://emedicine.medscape.com/article/1126725-workup