The nature of the characteristic cementum-like matrix deposits in the walls of simple bone cysts

Simple bone cysts (SBC) are benign tumour-like lesions, generally occurring in the metaphyses of long bones before skeletal maturity. Remarkably, in 10-70% of cases, a peculiar, amorphous and hypocellular matrix is found in the walls of SBCs which is usually regarded to consist of (calcified) fibrin clots in the literature. Because these deposits are strongly fuchsinophilic in routine van Gieson stains, the aim of this study was to investigate a series of SBCs using immunohistochemistry and electron microscopy.