**3. Indications of scalp biopsy in diagnosis of hair loss**

Scalp biopsies can be used to make or confirm a diagnosis of alopecia. Scalp biopsy is consid‐ ered mandatory in all cases of scarring alopecia. The interpretation of the histopathological findings of primary scarring alopecias without known clinical history may be difficult and this is especially true if the biopsy specimen is inadequate.

In non-scarring type, it is not difficult to diagnose these disorders. However, scalp biopsy can be needed in few cases of:


Figure 1. 32 year old female patient presented with diffuse, acute severe hair loss and with localized patch of alopecia areata as it demonstrated by red arrow. **Figure 1.** year old female patient presented with diffuse, acute severe hair loss and with localized patch of alopecia areata as it demonstrated by red arrow.

It is a crucial to determine the appropriate site of a scalp biopsy to have a correct diagnosis of alopecia, and this approach is different in scarring and non-scarring types. For a scarring process, the biopsy should be taken from the active border of hair loss where some hairs still remain and are more likely to display diagnostic findings. For non-scarring alopecias, the preferred site of biopsy is generally the border of a lesion (positive exclamation marks in alopecia areata), or from the site of a positive pull test in the setting of a diffuse alopecia. In the setting of evaluating a possible androgenic alopecia, two biopsies, one from the involved

The current gold-standard for a scalp biopsy specimen is the use of a 4-mm punch and must include subcutaneous fat to ensure sampling of the entire follicular unit and any anagen follicles; the specimen may be sectioned vertically or transversely [2]. Although

Vertically-sectioned punch biopsy specimen is adequate for assessing alopecias associated with interface changes, lichenoid infiltrates, and subcutaneous pathology [3]. However, vertical sectioning will show only 10% of the follicles present in the specimen

[4]because the hair follicles, which grow at an angle, cannot be visualized in their entirety in conventional vertical sections.

scalp (often vertex) and one from the uninvolved scalp (often occiput; serves as a positive control) may be beneficial.

a combination of the two may be optimal, the pathologist is frequently only provided with a single specimen.

**4. Technique of scalp biopsy** 

**5. Vertical sections**

Figure 2. Vertical section of a scalp biopsy from a patient with DLE.
