Myositis Ossificans Wheeless

Description: Myositis Ossificans (Sterner's Tumor) Discussion: - extra-skeletal ossification that occurs in muscles & other soft tissues - can be traumatic (75%), non traumatic, or progressive; - severe blunt trauma causing an intra-muscular hematoma may result in delayed ossification; - involved muscles: quadriceps, brachialis, and deltoid are involved most often; - typically lesions are distant from joints, have decr pain w/ time; - typically occurs in adolescents as a painless, enlarging mass in upper arm, thigh, or buttocks; - associated with an intact cortex; - demonstrate a zonal pattern; - histology: - microscopic, hypercellular spindle cells, peripheral woven bone, surrounding diseased & often trapped muscle, and normal osteoblasts making bone are typical; - zonation from central immature fibrous tissue to peripheral mature bone is characteristic, and helps distinguish myositis ossificans from osteosarcoma, where the central bone is likely to be mature;