Abstract
Recent experience with heterotopic ossification on the laparotomy scar in a 61-year-old man is described with some discussion on the etiology. There was a history of undergoing gastrectomy with an upper middle line incision 13 years before. About 5 years after the operation he had a nodular mass extending from the end-to-end of the incisional scar, and then about 8 years later the lesion was removed because it might cause disturbance of passage in the upper gastrointestinal tract. The removed specimen was 16×3.3×2.8 cm in size, and showed microscopically the bone and cartilagineous tissues with the marrow. Various hyposeses would offer various explanations on the etiology of this disease. From histopathological analysis we employed one that this heterotopic ossification was undertaken under the metaplastic origin. In other words, the old hyalinous scar tissues became calcified lesion as matrix for Ca-deposition and such calcified lesion developed to mature bone tissues due to metaplastic osteoblasts derived from regional immature mesenchyma cells.
