Introduction

Pathologists who deal frequently with skin biopsies are sometimes called upon to evaluate scalp biopsies from patients carrying the clinical diagnosis of "alopecia". Alopecia, or hair loss, is broadly divided by experienced dermatologists into clinical "scarring" and "non-scarring" varieties. More precise classifications, however, often necessitate one or more biopsies to yield a clinically useful diagnosis.

For many pathologists, a clinical history of alopecia is enough to prompt an immediate consultation with a dermatopathologist. While dermatopathologists are trained to recognize many types of alopecia, the diagnostic exercise is not nearly as mysterious as some would think. Much consternation could be avoided if pathologists would follow the basic steps outlined in this brief tutorial.

• Part 1 of the tutorial covers optimizing the information from limited biopsy material, and properly orienting and leveling the paraffin blocks.
• Part 2 of the tutorial covers the microanatomy of the hair follicle as cut in longitudinal (or vertical) sections.
• Part 3 covers the microanatomy of the hair follicle in transverse (or horizontal) sections.
• Part 4 covers several common conditions, which, taken together, represent the majority of diagnoses encountered in typical dermatologic specimens arriving with the clinical diagnosis of "alopecia."

In addition, a reference section is provided for the curious.