Accordingly, HO is formed by fibroblasts in the granulation tissue of necrotic nests; and calcium deposition adjacent to heterotopic ossification in mucin is suggested to play an important role in HO.11–13 Furthermore, osteoid matrices are observed in stromal and tumor cells, suggesting that factors secreted by tumor cells cause pluripotent stromal cells to metamorphose into osteoprogenitor cells. The gene discussed is MUC5AC; the disease is neoplasm.