Figure 1.
Figure 2.
The usual biopsy procedure performed for evaluation of alopecia is a punch biopsy. Ideally, the punch biopsy should be at least 4 mm in diameter, and optimally, 6 mm in diameter. The biopsy should be obtained from an area in which there are still residual hair follicles. Biopsies from the center of scarred alopecias reveal little in the way of the underlying disease process. The biopsy tool should be inserted parallel to the direction of hair growth and advanced deeply into the subcutis.
If more than one biopsy is taken, the optimal information can be gathered by embedding one biopsy vertically and the other horizontally. If only one biopsy is obtained, the greatest amount of information can be gathered from a horizontally-oriented specimen. Dermatologists should check with the dermatopathologist who will be interpreting the specimen, as procedures for labeling the specimen bottle(s) may vary from laboratory to laboratory. In addition, not all dermatopathologists are comfortable with interpreting horizontally-oriented specimens.
Vertically-oriented specimens are prepared by halving the biopsy cylinder along its long axis (figure 1), and embedding the cut faces down in the paraffin block (figure 2). Should there be a possible need for direct immunofluorescence (DIF) examination, one of the halves can be preserved in Michel's (or another appropriate) fixative. Check with your local laboratory for the appropriate fixatives. DIF cannot be performed on formalin-fixed material.
Figure 1.
Figure 2.
The resulting sections utilizing the method outlined above will be layed out like this:
The advantage of this orientation is that the follicle can be examined in its entire length in one slide (if the punch biopsy is well-oriented). The disadvantage is that multiple levels will usually be required to reach a conclusion about the diagnosis as only 4 to 8 follicles can be examined in a single slide.
Horizontally-oriented specimens are prepared by halving the biopsy cylinder along its midriff, 0.5 to 1.0 mm below the dermal-epidermal junction. Again, each of the cut surfaces is embedded face down in the paraffin block (figure 3). Obtaining six levels through the paraffin block (with multiple profiles per glass slide) generally results in adequate sampling of the horizontally-oriented tissue.
Figure 3.
The resulting sections utilizing the horizontal embedding method will be layed out like this:
The advantage of this orientation is that all follicles can be examined at multiple levels. In a typical normal biopsy specimen nearly 40 follicles can be visualized in this manner. One disadvantage is that the entire block is leveled, so should special stains be required, one of the H&E sections must be destained and restained to complete the desired evaluation. This can be avoided by obtaining unstained slides at the time levels are cut for possible future use. In addition, it can sometimes be difficult to visualize the dermal-epidermal junction on horizontal sections.