EXPERT ANALYSIS FROM THE AAD SUMMER ACADEMY 2016
BOSTON (FRONTLINE MEDICAL NEWS) – Getting a proper scalp biopsy and providing the dermatopathologist with a good supporting history are important elements in diagnosing a patient with hair loss, according to Eleanor Knopp, MD, a dermatologist and dermatopathologist with Group Health Permanente, Seattle.
The keys to a good scalp biopsy in a patient with alopecia are to take an adequate sample of scalp in both size and degree of involvement. With regard to where to biopsy, “it’s important … to select an area of advanced thinning if you’re doing a biopsy of a nonscarring alopecia,” Dr. Knopp said at the American Academy of Dermatology summer meeting. She advised being “generous” with an anesthetic, preferably one containing epinephrine, to help keep the wound dry and to help with visualization during the procedure.
A 4-mm punch biopsy has almost twice the surface area of a 3-mm biopsy (12.6 mm2 compared with about 7 mm2), she pointed out. With the larger biopsy, “the patient is not going to know the difference … and I get so many more follicles to look at as a pathologist,” she said, “so that’s a really easy increased bang for your buck.”
Evaluating for the presence or absence of follicular ostia with a dermatoscope helps distinguish scarring from nonscarring alopecia. Scarring alopecias typically show loss of follicular ostia, she noted.
While this method is effective at identifying nonscarring areas in white patients, it can be difficult to appreciate the disappearance of follicular ostia with a dermatoscope in patients of African descent or patients with darkly pigmented skin. In these patients, eccrine ostia appear as white pinpoint dots under a dermatoscope and mimic the appearance of follicular ostia, despite the presence of scarring alopecia, she noted.
In this situation, Dr. Knopp said the threshold for biopsying patients with darkly pigmented skin should be lower to rule out an early cicatricial alopecia.
For any specimen sent to the dermatopathologist, it is important to note patient characteristics, including age and race, duration of the condition, and clinical pattern. Not only is race helpful for interpreting what is seen in the specimen, but certain racial groups have higher predilections for certain diseases. There are also differences in normal hair densities depending on race although there can be a wide range even within a race, she added. Providing a photo of the involved area of the scalp is also a good idea, she added.
When biopsying a scarring alopecia, Dr. Knopp said that her preference is to find an area of relatively early thinning with visible erythema, and scale if it is present, “so that you know you have active inflammatory disease, but it’s not so advanced that you’re just seeing end-stage changes of scarring.”
It is worth having a discussion with the dermatopathologist about sectioning specimens, Dr. Knopp said. The consensus among most dermatopathologists is that horizontal sections are “absolutely the way to go for nonscarring alopecias,” but some dermatopathologists strongly prefer vertical sections, especially in cicatricial alopecias. Clinicians can always choose among the many reference laboratories to obtain the type of sections they prefer.
In cases of cicatricial alopecia, Dr. Knopp cautioned that clinicians may see “juicy pustules or fluctuant nodules” and consider these findings indicative of a highly active area of disease, but these changes may obscure early findings that are helpful to a pathologist. A better choice for a biopsy site is an area of early involvement that is not too inflamed and not so advanced that it is just scar, she noted.
Another potential pitfall is the temptation to biopsy a tuft of hairs. If there is polytrichia or compounding of follicles, it may be tempting to fit the punch tool over what are also sometimes called “doll’s hairs.” But those structures are nonspecific, end-stage features of many different cicatricial alopecias, including lichen planopilaris, central centrifugal cicatricial alopecia, and even lupus. Instead, Dr. Knopp recommended taking a specimen at the periphery where compounding is not present but where there is thinning and active inflammation.
Dr. Knopp, also with the University of Washington, Seattle, reported no financial relationships.
