ABSTRACT
Most specimens obtained for the diagnosis of hair loss should be sectioned transversely (horizontally). The technique of transverse sectioning is unfamiliar to many pathologists, and so it will be useful to discuss its rationale. Vertical sections are of limited value in the study of hair disease because the number and type of hairs found on a vertical section are subject to considerable sampling error. The information obtained from vertical sections is usually incomplete and often misleading, as demonstrated in Figure 3.1. A vertical section bisecting the specimen through plane ‘X’ would sample only four follicles out of a total of 28 contained in the specimen. A section through plane ‘Y’ would not sample any follicles. In many cases of alopecia, the diagnosis hinges on just a few follicles. The chance of ‘hitting’ these follicles on a routine vertical section is slim. Accurately counting follicles is nearly impossible using vertical sections, so quantitative data cannot be gleaned in this way.
