FOS and myositis disease: Proliferative fasciitis and myositis is the lesions that composed of ganglion-like fibroblast cells that seen in the background of nodular fasciitis-like appearance or checkerboard-like appearance with degenerating skeletal muscle that alarming RMS, however, these lesions may express actin and some histiocytic markers and lack expression of desmin, Myo-D1 and Myogenin [66, 67], in addition, a small subset of cases can characteristically express c-FOS protein and genetically harbor FOS gene re-arrangement [68].