Polarized microscopy as a helpful tool to distinguish chronic nonscarring alopecia from scarring alopecia.

BACKGROUND Nonscarring alopecia differs from scarring alopecia on pathologic examination by the preservation of follicular units and lack of follicular dropout. However, long-standing cases of active nonscarring hair loss can show follicular dropout on pathologic examination and can be difficult to interpret. OBSERVATIONS We describe a patient with nonscarring alopecia that was misdiagnosed as scarring alopecia due to difficulty in distinguishing between scarred tracts (follicular dropout) and long-persisting fibrovascular streamers. Polarized light microscopy permits us to distinguish follicular scars from fibrous streamers because the fibrous streamers are birefringent negative for collagen. The main advantages of polarized microscopy are that it is fast and cost free and can screen all sections within minutes; it is also easy to interpret for beginners because there is a built-in control of birefringent-positive dermal collagen. CONCLUSION Polarized light can be used in the pathological evaluation of hair loss to distinguish between the follicular scars in scarring alopecia and the fibrovascular streamers in long-standing nonscarring alopecia.