The Scalp Biopsy: Angle of the Punch Tool is Important!
Directing the Angle of the Scalp Biopsy
A “punch biopsy” is the preferred way to biopsy the scalp if a biopsy is indeed needed. The biopsy should be 4 mm in diameter and should ideally enter the skin at a very precise angle. The angle of entry of the punch is the angle that the hairs emerge. The angle allows the pathologist to obtain the greatest amount of information when the interpret the biopsy at a later date.
I like to trim the hairs in the area I wish to biopsy to 3 mm. This causes the trimmed hairs to “pop up” and gives me a more precise ability to position my punch biopsy tool directly over top of the hairs at the same angle they emerge. I try not to trim too many hairs as patients do not like having any reduction in perceived hair density after the biopsy. Trimming just a few hairs usually suffices. The biopsy site can be sutured or left open to heal with secondary intention although I prefer to suture.
I’m often asked “What if the biopsy site does not contain hairs?” to which I reply the biopsy site should ideally always contain hairs. If one is performing a biopsy to evaluate for hair loss, the chosen biopsy site should always contain hairs! Biopsies of sites devoid of hair are usually not so helpful.
This article was written by Dr. Jeff Donovan, a Canadian and US board certified dermatologist specializing exclusively in hair loss.