Abdominal fibromatosis arises in the abdominal wall in women of child-bearing age. Some cases have occurred in children or adult men. The usual location is rectus abdominis or internal oblique muscles. It often occurs during pregnancy or within first year after childbirth. Its pathologic features are identical to those seen in other locations. The lesions do tend to be smaller and often less aggressive than extra-abdominal fibromatoses. The image shows interlacing bundles of fibroblasts separated by small amounts of collagen.