 Brown tumours consist of fibrous tissue, woven bone and supporting vasculature, but no matrix.The osteoclasts consume the trabecular bone that osteoblasts lay down and this front of reparative bone deposition followed by additional resorption can expand beyond the usual shape of the bone, involving the periosteum thus causing bone pain.The characteristic brown coloration results from hemosiderin deposition into the osteolytic cysts.