HSP47 is a useful marker for skin fibroblasts in formalin-fixed, paraffin-embedded tissue specimens

Aim: This study was undertaken to assess whether heat-shock protein (HSP)47 is a useful cell marker for skin fibroblasts in formalin-fixed, paraffin-embedded skin specimens. Background: HSP47, a 47-kDa HSP, is a collagen-specific molecular chaperone localized in the endoplasmic reticulum. HSP47 plays an essential role in collagen biosynthesis in skin fibroblasts. Methods: Immunohistochemistry was performed to detect HSP47 in skin fibroblast cultures and skin tissue sections. Results: Immunostaining for HSP47 clearly detected skin fibroblasts in paraffin tissue sections as well as in fibroblast cultures and frozen tissue sections. HSP47 staining on paraffin sections from diseased skin specimens revealed that skin ulcer, keloid, nodular fascitis, spindle cell lipoma, and dermatofibroma had strong signals for HSP47 compared with the signals obtained from normal skin. Dermatofibrosarcoma protuberans had many HSP47 positive cells, but signals on individual cells were not as strong as those seen from the above benign proliferative disease samples. In neurofibroma, a small number of faintly positive cells were detected. Our double-immunostaining studies also demonstrated that HSP47 staining distinguished skin fibroblasts from CD68-positive histiocytes/macrophages, factor VIII-related antigen-positive endothelial cells, or factor XIIIa-positive dermal dendritic cells. CD34-positive interstitial cells coexpressed HSP47 in spindle cell lipoma. Conclusions: These findings indicate that HSP47 staining can detect skin fibroblasts in routine, paraffin-embedded specimens. A panel approach using HSP47 and other cell markers on paraffin sections may help the identification of the cell type involved with mesenchymal proliferative disorders.