The Essential Components of the Scalp Biopsy Report

What should pathologists be including in the biopsy report?

Interpreting scalp biopsies is not easy. It requires specific expertise and I’m fortunate to work with amazing pathologists. Every day, I receive biopsy reports from around the world for patients that want advice with their hair. Some reports are so clear, I’m mesmerized and feel like I’m right there sitting at the microscope. Some reports are so nice I want to print them out and frame them. 

And then there are reports that look nice but aren’t nice. They have a lot information in them but lack the key information to help you decide as a clinician what the real diagnosis is. Last week, I read a long report where the pathologist was trying to decide whether the case was a case of lichen planopilaris …. or not!! The report discussed a lot of good information - but lacked information about the presence or absence of sebaceous glands which probably would have solidified the diagnosis. I felt frustrated but hopefully when I see the patient in a few weeks we’ll know if it’s a scarring alopecia simply by looking at the scalp. Sometimes in these types of cases, a biopsy was not even needed. Biopsy reports that are lacking key information don’t matter if the diagnosis is obvious. But these sorts of biopsies are frustrating in cases where the diagnosis is challenging. It’s like reading a good book and being three-quarters of the way through the book only to find that the publisher of the book forgot to print a few chapters. 

So what makes a good report, anyways?

There’s one main criteria that makes up a good report. The report must be helpful to the clinician and helps rule out other issues.Below, I’ll outline the key parts of a scalp biopsy.

SECTION 1: What’s the quality of the biopsy? and How was the biopsy processed?

The first section of the biopsy usually begins by confirming the size of the biopsy and whether the biopsy was taken properly by the doctor and was deep enough and whether it was taken parallel to the hairs or whether the clinician took it in a manner that cut through all the hairs. When I read reports from other physicians, I like knowing about the size of the biopsy. If a 2 mm biopsy was taken instead of the standard 4 mm biopsy, this is important to know. A tiny 2 mm biopsy might be taken to try to limit the patient’s chance of developing a visible scar - but that tiny biopsy is going to be limited in the amount of information it can give. 

The report then describes whether the biopsy was obtained with vertical or horizontal sections by the lab. That’s helpful to put things into context for the reader of the report. If the biopsy was taken using horizontal sections, it’s going to be possible to count the number of hairs fairly accurately and so I’ll be waiting for some information on hair follicle numbers as I read more. If the biopsy was processed using vertical sections, this information is simply not possible and I won’t be expecting this as a read the report. 

SECTION 2: What’s the pathologist’s feeling about the hair density? 

It’s nice to get a sense from the start if the pathologist feels hair numbers are reduced compared to normal. If horizontal sections were used, the pathologist may actually count the total number of hairs he or she sees and make a comment about density. If vertical sections are used, accurate measurements of density are not going to be possible, but the astute pathologist may still make a comment if density appears reduced. 

SECTION 3. Is there INFLAMMATION in the biopsy? If so, where exactly is it .. and where exactly is it not?

Inflammation can be very relevant to the diagnosis. But the key information needed from the pathologist is where exactly is this inflammation. 

a) Is the inflammation perifollicular? and if so is found at the level of the isthmus, infundibulum or bulb .. or even deeper? 

Perifollicular inflammation is common in many conditions and in and of itself doesn’t mean much. Perifollicular inflammation around the isthmus can be seen in scarring alopecias and in androgenetic alopecia too. Inflammation around the bulb is often seen in alopecia areata. Deeper inflammation (below the bulb) can be seen in dissecting cellulitis, various infiltrative conditions and in the diseases of the fat. 

b) If there is inflammation, is any ‘lichenoid’ in nature?

if the pathologists does. find inflammation at the level of the isthmus, it’s helpful to know if that inflammation is causing hair follicle keratinocytes to die or not. Evidence of such “lichenoid” involvement is important. It’s not always seen even in cases of lichen planopilaris - but the presence of epithelial cell necrosis is important to know about if it’s present. 

c) How much inflammation is present?

It’s helpful to get a sense if there is just a bit of inflammation or whether the biopsy is plugged tight with inflammation. In the case of a scarring alopecia, severe degree of inflammation are probably best handled with systemic treatments (although more studies are needed in that regard). 

d) Is there any other inflammation seen anywhere else?

The pathologist may not comment on other inflammation but we hope he or she has looked for it. Inflammation around blood vessel (perivascular inflammation) and around eccrine glands (perieccrine inflammation) is helpful in some autoimmune issues. 

SECTION 4. Is there FIBROSIS (scarring) in the biopsy? If so, where exactly is it .. and where exactly is it not?

It’s important to have a sense of whether or not the biopsy shows evidence of increased scar tissue. We call. such scarring fibrosis. In scarring alopecias like lichen planopilaris, the scar tissue is initially just around the hair follicles and the majority of the dermis is not involved with any scarring whatsoever. In other scarring  alopecias like folliculitis decalvans, the areas between the follicles are also involved with scarring. 

SECTION 5. Are the sebaceous glands reduced or affected in any way?

Unfortunately, comments about the sebaceous glands are frequently omitted from many scalp biopsy reports I see. Sometimes it does not matter. The biopsy is a biopsy of scarring alopecia and all the other features in the report go together to say the same thing - this patient has scarring alopecia. 

In many cases (particularly tough cases!), however , information about the sebaceous glands would have helped a lot to figure out challenging cases of hair loss. 

Reduction in sebaceous glands is very much a feature of many of the scarring alopecias. Perifollicular fibrosis and perifollicular inflammation can be seen in both scarring alopecia and in androgenetic alopecia but only the scarring alopecias are going to show loss and reduction of sebaceous glands. 

SECTION 6. Is there miniaturization of hair follicles? If so, it is a spectrum of miniaturization or are all the thin hairs mainly one size? If the lab used horizontal sectioning, what is the T:V ratio?

The findings of a spectrum of hairs of different calibers that are rooted to different depths in the skin (i.e. miniaturized, vellus-like follicles) often signals that some degree of androgenetic alopecia might be present. The finding of miniaturized vellus hairs that are all one caliber (rather than a spectrum of different calibers) and all one depth (rather than a spectrum of different depths) in the skin may in some cases suggest a diagnosis of alopecia areata. 

Miniaturized, vellus-like follicles can be seen with specimens processed with both vertical sections and horizontal sections. The benefit of horizonal sections is that the pathologist can add up all the terminal hairs and add up all the vellus hairs and provide an estimate of the so called terminal to vellus ratio. 

The normal T:V ratio is between 6:1 and 8:1. A T:V ratio less than 4:1 is suggestive of a diagnosis of androgenetic alopecia. A T:V ratio that is above 8:1 is suggestive of a diagnosis of chronic telogen effluvium. 

SECTION 7. If the lab used horizontal sectioning, what is the percentage of hairs in catagen and telogen phases?

It’s often very helpful to have information on the proportion of hairs in telogen phase.Often the numbers can be normal even if clinically the patient seems to have a telogen effluvium. Nevertheless, if the proportion of hairs in telogen is increased well above 15 % , this is indicative that a telogen effluvium is present. In addition, one needs to look carefully at information the pathologist provides about the proportion of catagen and telogen hairs. An increased proportion of hairs in the catagen and telogen phase is often seen in alopecia areata as well. 

SECTION 8. Is the epidermis normal? 

The epidermis or the very top of the patient’s scalp can also be affected by a variety of issues and inflammation about what’s happening in the epidermis is very important. Information about psoriasis and seborrheic dermatitis and other infectious issues can come from careful review of the findings of the epidermis. 

SECTION 9. Are any special stains needed? What were the results?

There are several special stains which can be very helpful in challenging cases, including PAS stain (Periodic Acid Schiff) , Verhoeff stain and Alcian Blue. The PAS stain can assist with identifying dermatophyte infections in the epidermis as well as basement membrane thickening in the case of autoimmune disease. Alcian Blue stains can identify patterns of mucin staining and highlight interstitial mucin that is typical of autoimmune diseases like dermatomyositis and lupus. Perifollicular mucin is often seen in and around the perifollicular fibrosis in lichen planopilaris, but not in the interstitial dermis. Verhoeff van Giesen stains can help identify scars from follicular streamers and from from the normal surrounding dermis. This stain can also identify patterns of elastin staining and fragmentation of elastin fibres that is seen in the scarring alopecias.

CONCLUSION

Scalp biopsies can sometimes be incredibly helpful when the diagnosis is not clear. But one must remember that they are samples of 30-40 hairs out of the 100,000 or so that were originally on the scalp. Biopsies are the the most helpful when the reports that come from interpreting the biopsy contain the right information.