Scalp biopsy is indicated when diagnosis is still unclear, and in all cases of cicatricial and non-cicatricial alopecia. It is performed under local anesthesia. The punch is 4 mm in diameter and it should be 4 mm deep so it includes follicular units and subcutaneous tissue. The tissue is then sent to a dermatopathologist for further analysis.
Biopsy is critical in all forms of alopecia-scarring and non-scarring. It is an important tool in diagnosing not only female pattern hair loss as wel as differentiating between trichotillomania versus alopecia areata. It is a predictor of possible regrowth in long standing alopecias (alopecia areata, post chemotherapy, androgenetic alopecia). It provides the doctor with the actual number of hair follicles and their stage so it is clear to differentiate androgenetic alopecia from chronic telogen effluvium.