MSH: A childhood counterpart of abdominal or extra-abdominal desmoid tumors, characterized by firm subcutaneous nodules that grow rapidly in any part of the body but do not metastasize. The adult form of abdominal fibromatosis is FIBROMATOSIS, ABDOMINAL. (Stedman, 25th ed),NCI: A tumor of the tissue that surrounds muscles, usually in the abdomen. A desmoid tumor rarely metastasizes (spreads to other parts of the body).,NCI: An insidious poorly circumscribed neoplasm arising from the deep soft tissues. It is characterized by the presence of elongated spindle-shaped fibroblasts, collagenous stroma formation, and an infiltrative growth pattern.