Scalp biopsy is mandatory in all clinically suspected cases of Primary Cicatricial Alopecia (PCA), particularly when the clinical picture does not allow a firm diagnosis. Specimens should be placed into formalin.
Two 4-mm punch biopsies following the direction of the hair shafts are taken lateral to the midline deep into the subcutaneous fat where anagen hair bulbs are located. One biopsy will be processed for conventional vertical sectioning; the other will be sectioned horizontally with respect to the skin surface.
Biopsies should be taken from clinically active, hair-bearing skin. Do not biopsy a completely bald, atrophic ‘end-stage’ area of alopecia.
The biopsy must also be deep enough to sample the whole terminal hair follicle (i.e. extend into the subcutaneous fat)
The preferred area for biopsy is the central scalp in an area representative of the hair loss process. Biopsies should not be taken from the bitemporal area as this region may have miniaturized hairs independent of AGA.