Infantile fibromatosis is most commonly noted by age 2, although some patients may be upto 8 yrs. old. It usually involves skeletal muscles of head and neck, upper extremity, and thigh. In the head and neck region, it may involve bone and may be mistaken for desmoplastic fibroma of bone. The image shows sheets of primitive fibroblasts separating skeletal muscle fibers. Lipocytes are also frequently found within the lesion (not shown here).