The human progenitor-cell antigen CD34 is expressed in dermal dendritic cells and is lost in several disorders affecting dermal collagen. The loss of CD34 immunohistochemical staining has been demonstrated to be helpful in the histologic diagnosis of morphea, lichen sclerosus, and the classic pattern of granuloma annulare. This study characterized CD34 expression in 2 sclerosing disorders affecting the subcutis: lipodermatosclerosis (LDS) and the sclerodermoid form of chronic graft-versus-host disease (ScGVHD). In addition, we applied CD34 staining to the interstitial pattern of granuloma annulare (IGA), which is a diagnostically challenging entity with subtle amounts of dermal collagen degeneration. Fifteen cases of LDS, 6 cases of ScGVHD, and 4 cases of IGA were identified and stained with CD34. All cases of LDS showed loss of CD34 within subcutaneous septa, and 9 cases (60%) also exhibited full-thickness dermal loss of interstitial staining. All 6 cases of ScGVHD showed varying degrees of CD34 loss within the dermis and/or subcutaneous septa. The normal subcutis showed diffuse septal staining with CD34, with a density equal to that seen in the dermis. CD34 staining was lost in areas of dermal inflammation in half of the IGA cases. We conclude that CD34 staining is a useful ancillary test in disease processes affecting the subcutaneous collagen such as LDS and ScGVHD. Its utility also extends to diagnostically challenging disorders of dermal collagen degeneration such as IGA.
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