BACKGROUND: A subgroup of macrophage related dermal cells expresses the pro-coagulation factor XIIIa, while others express the anti-coagulation cofactor thrombomodulin. These cells can be involved in inflammatory and reparative tissue events. OBJETIVES: We investigated the participation of factor XIIIa+ dermal cells and thrombomodulin+ (TM+) dermal cells in the histopathological picture of granuloma annulare which is characterized by collagen necrobiosis and macrophagic infiltrate. METHODS: The histopathological picture of granuloma annulare observed in 23 skin biopsies was classified according to presence of complete or incomplete collagen degeneration and distribution of dermal infiltrate. Factor XIIIa+ dermal dendrocytes and thrombomodulin+ dermal cells were recognized by specific antibodies applied in immunohistochemical protocols; a macrophage marker (CD68) was also used. Distribution of distinct cell subsets were observed and semiquantitative analysis performed. RESULTS: Factor XIIIa+ dendrocytes were rarely detected in the lesion while thrombomodulin+ and CD68+ cells represented a considerable part of cell infiltrate. They were seen at its periphery (palisade arrangement), among degenerated collagen or diffusely distributed. A tendency was noted for association between higher semiquantification of thrombomodulin+ cells and both lower semiquantification of FXIIIa+ dendrocytes and histological type II. Dermal dendrocyte hyperplasia around the lesion was detected. CONCLUSION: The different tissue distribution of the FXIIIa+ cells and TM+ cells could reflect their distinct and complementary roles in the recovery of dermal tissue and in the lesion evolutive process in granuloma annulare.
factor XIIIa; granuloma annulare; thrombomodulin
