Clinical pearl: Punch biopsy technique for alopecias.

Clinical problem

A thorough history and physical examination is often sufficient for diagnosing alopecia. However, in circumstances in which clinical findings are ambiguous, or there is concern for disease that requires intensive management, a scalp biopsy may be required. Histopathologic examination is useful for distinguishing etiologies of hair loss; however, only when biopsies have been performed using a proper technique.

Therapeutic solution

With thoughtful selection of a biopsy site and proper biopsy technique, it is possible to capture disease activity and make an accurate histopathologic diagnosis. When a nonscarring process is suspected, the biopsy should be performed at the center of a lesion, where there is maximal hair loss. Conversely, if a cicatricial process is suspected, the biopsy should be taken at the margin, where there are signs of active inflammation on trichoscopy, but still hair present. Areas with complete hair loss are in the later stages of fibrosis and may be nondiagnostic when sampled. A site with significant inflammation or pustular lesions will also be nondiagnostic; adjacent, less involved tissue should be selected.[1] Before taking the biopsy, a patient’s medications should be reviewed; immunosuppressive medications, including intralesional, topical, and oral therapies, may be withheld in the time leading up to the biopsy, as their anti-inflammatory effects have the potential to confound pathologic assessment, especially for inflammatory processes. If the alopecia affects the frontal hairline, consideration should be given to choosing a site that will yield an acceptable cosmetic outcome.[2]

The biopsy should be performed using a 4-mm punch through the subcutaneous fat to the hub of the instrument. Attaining adequate depth and cutting the tissue beneath the hair bulbs is necessary to avoid damaging the hair follicles.[2] A 4-mm, rather than a 3-mm punch is utilized because a 3-mm punch prohibits comparison of follicular density to established standards.[2,3] The punch must be angled parallel to the direction at which the hair exits the skin surface, rather than perpendicular to the scalp, to avoid transecting the follicles and maximize diagnostic yield on transverse sectioning[1] (Figs. 1 and 2).

Fig. 1.

Correct biopsy technique. (A) Correct biopsy technique: punch is angled parallel to direction at which hair exits skin surface. (B) Correct biopsy technique: specimen is cut parallel to the epidermis so that the base of the specimen is flat and includes all terminal hairs.

Fig. 2.

Incorrect biopsy technique. (A) Incorrect biopsy technique: punch is angled perpendicular to the scalp, transecting hair follicles. (B–D) Incorrect biopsy technique: partial specimens which are too superficial or include a frayed base make it difficult to perform adequate microscopic evaluation.

Conflicts of interest

Dr. Shapiro is a consultant for Aclaris Therapeutics, Incyte, and Replicel Life Sciences. Drs. Shapiro and Lo Sicco have been investigators for Regen Lab and are investigators for Pfizer. Dr. Lo Sicco is a consultant for Pfizer. Dr. Brinster and Elizabeth Klein have no conflicts of interest to declare.

Funding

None.

Study approval

N/A.