Do we need 2 scalp biopsies or just one for diagnosing hair loss?

How many scalp biopsies should I be getting?

I’ve selected this question below for this week’s question of the week. It allows us to review some concepts in scalp biopsies for hair loss.

Question

Hi Dr. Donovan. I am confused about how many scalp biopsies a person should get to diagnose hair loss. Some people say one biopsy is needed and some people say two is better. So I ask you - how many biopsies does a person with hair loss really need?

Answer

Great question. Thank you!

Well, the short answer is that one should have as many biopsies as it needs to figure out the diagnosis. That ranges from zero biopsies to somewhere around four or five. Most commonly, it’s zero and the runner up choice is one or two. Only rarely are three or four or five biopsies ever needed.

But let’s dive into this great question.

Let me begin by saying that I don’t perform a scalp biopsy with every single patient I evaluate. Maybe 1 in 20 or 1 in 25 patients will need a scalp biopsy. Most of the time, I can confirm the diagnosis (or diagnoses) by listening to the patient’s story, and fully examining the patient’s scalp. A full examination of the scalp means I’ve examined the patterns of hair loss PLUS made use of trichoscopy or a type of magnification. With trichoscopy, we can diagnose many hair loss conditions that we use to struggle with before trichoscopy.

So, the more and more skills that clinicians develop in the use of trichoscopy, the fewer and fewer scalp biopsies they end up doing. Trichoscopy is powerful tool!

So, if I’m 100 % confident in the diagnosis after listening to the patient’s full story and examining his or her scalp, we don’t need a biopsy. That’s straightforward.

So guess what? In 95% of patients that come into the office, I’m 100 % confident in the diagnosis after listening to the patient’s full story and examining his or her scalp. So in 95 % of cases, we don’t need a biopsy.

What about the other 5 %?

The other 5 % of patients, we need a biopsy! I perform a biopsy if the diagnosis is not clear. Generally speaking, I take a biopsy when I’m trying to differentiate between two or three different scalp conditions that look the same. I might be trying to differentiate between a patient who has either discoid lupus or lichen planopilaris. I might be trying to differentiate between androgenetic alopecia and fibrosing alopecia in a pattern distribution. I might be trying to differentiate between alopecia areata incognita and telogen effluvium or androgenetic alopecia. Generally speaking I’ll take a single biopsy when I need the pathologist’s help to distinguish between two of three hair conditions that might look similar.

If the scalp looks all the same in all areas of the hair loss, then generally I will take only one biopsy. If there are different areas that look somewhat different, I may take two biopsies. For example, if one area of the scalp has pustules and another area is scaly or has comedones or scales, I might consider two biopsies. If there is concern for infection, I may take a third biopsy and send a piece of the biopsy off to the microbiology lab to try to grow up any organism. (Sometimes I just cut a little piece from one of the other biopsies to send off to the microbiology lab rather than take a whole new piece). But you can quickly see how two biopsies can become three.

In some cases, I may take a few biopsies because I know the disease has different stages and I’m trying to capture different stages. Some of the autoimmune blistering diseases are like this.

In addition, sometimes I’ll need a fresh piece of biopsy for a special staining technique called direct immunofluorescence (DIF). Most biopsies of the scalp get dropped into a preservative called formalin. We can’t drop biopsies that will be processed for DIF in formalin or the procedure won’t work. Therefore, we need another piece. This piece of tissue floats off to the pathology lab in a completely different bath water. Instead of formalin, we use a liquid called Michel’s media.

Finally, sometimes I need many biopsies to try to really capture hair cycle dynamics and the proportion of terminal and vellus hairs. In some cases of chronic telogen effluvium, having several biopsies capturing a T:V ratio of 8:1 or more really helps solidify that diagnosis. Sometimes we can’t get this kind of accuracy with just one biopsy.

Generally speaking though, I usually take a single biopsy. Our lab will cut this single biopsy into both vertical and horizontal sections using a technique called the HoVert technique. Our pathologists don’t need one piece for horizontal sectioning and one separate piece for vertical sectioning.

There are situations where a biopsy comes back somewhat helpful but not nearly as helpful as you might have first imagined. In many cases, I did the biopsy myself so I know it was in a good spot. In this case, I may want to do another biopsy.

In summary, you can easily see how the plan to do one biopsy can turn into two or three or four different samples if there is different morphology on the scalp or we need different analyses done (like culture for infection) or direct immunofluorescence). In general, if I am going to do a biopsy, I usually do one biopsy 85% of the time and two biopsies 15 % of the time. I don't just to two biopsies routinely because it sounds like a good plan. Studies show it often does not add much to the diagnosis.

Thanks again for the wonderful question!