Random Biopsies are Rarely Helpful
Where on the scalp should my doctor take a biopsy sample?
This is an important question as random biopsies from "just anywhere" are generally not very helpful. First, it must be stated that biopsies are not needed in most patients with hair loss. Secondly, it must also be stated that not enough patients have scalp biopsies! A biopsy should be taken from the area that is undergoing the most change. If it is decided that a biopsy is needed to exclude androgenetic alopecia (AGA), biopsies should be taken from the front, middle or top (depending on where the most change is happening). A biopsy from the very back might show changes of AGA if present - but more significant degrees of change would always be up front rather than in the very back. In suspected scarring alopecia, a biopsy should first and foremost be taken from where the dermatologist sees evidence of the condition. This is best assessed with an instrument called a "dermatoscope." Changes of scarring alopecia include redness around hairs, scaling, scarred areas, sometimes pustules and crust. The biopsy must always contain hairs as biopsies of completely scarred areas are useless. For conditions that affect the entire scalp (like acute and chronic telogen effluvium) the biopsy should be taken from the mid scalp to better assess hair cycle characteristics (anagen and telogen ratios) and to detect conditions that mimic CTE including androgenetic alopecia and lichen planopilaris (LPP). The three "X's" in the picture show where I would typically take a biopsy to assess for CTE. Note that these biopsies are not taken from the temples - even if the patient states this is where most of the hair loss has occurred. (A separate biopsy from the temple could be considered). This allows the dermatpathologist to best assess the terminal and vellus ratios (T:V ratios). A T:V ratio above 8:1 taken from the mid scalp is highly suggestive of a diagnosis of chronic telogen effluvium. A T:V ratio less than 4:1 is more in keeping with androgenetic alopecia.
Biopsies always leave a small scar. One should consider performing a biopsy away from the central "part" if at all possible as many women make use of a central part to style their hair.
Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Vancouver office at 604.283.9299