Dilation of Multiple Eccrine Ducts as a Highly Specific Marker for Cicatricial Alopecia

BACKGROUND: Eccrine duct dilation (EDD) was recently described to occur more frequently in cicatricial alopecias than noncicatricial alopecias. Because single EDD can be useful in the evaluation of alopecias, we aimed to determine whether dilation of multiple eccrine duct units, or "multiple eccrine duct dilation (MEDD)," could more specifically discriminate between cicatricial and noncicatricial alopecias. METHODS: We retrospectively evaluated 611 scalp biopsies (342 cicatricial alopecias and 269 noncicatricial alopecias). RESULTS: Among cicatricial alopecias, MEDD was found in 21% (25/118) of central centrifugal cicatricial alopecia, 26% (29/109) of lichen planopilaris, 13% (10/73) of discoid lupus erythematosus, 31% (5/16) of acne keloidalis nuchae, and 26% (7/26) of folliculitis decalvans. In noncicatricial alopecias, MEDD was found in 1% (1/102) of androgenetic alopecia, 0.7% (1/150) of alopecia areata, and 0% (0/17) of telogen effluvium. In cicatricial alopecias, MEDD occurred in a significantly higher frequency (22%; 76/342) compared with noncicatricial alopecias (0.7%; 2/269) (P-value <0.0001). The presence of MEDD correlated with a diagnosis of cicatricial alopecia with 22% sensitivity and 99% specificity. MEDD also occurred more frequently in cases with moderate to severe inflammation and fibroplasia, suggesting that EDD is a reactive change secondary to the scarring processes. CONCLUSION: The presence of MEDD on scalp biopsies may be a highly specific marker of cicatricial alopecia and can aid in rendering a more accurate diagnosis. MEDD without other definitive histopathologic features of cicatricial alopecia may compel pathologists to pursue additional workup and/or raise the possibility that a cicatricial alopecia cannot be entirely excluded.