Low Grade Myofibroblastic Sarcoma Occurred in the Scalp

growing palpable hard mass in the right parietal scalp.He had no past history of scalp trauma or neoplasm.On physical examination, there was a 3×4 cm hard mass that was mild tenderness.Enhanced computed tomography (CT) scanning of head showed a well-defined and heterogeneously enhancing scalp mass (Fig. 1).The patient underwent excision of the tumor with macroscopically clear margins.The mass was relatively well-circumscribed, firm, and grayish with fibrous.Histological examination revealed a spindle cell tumor with interspersed collagen bundles.The spindle cells show moderate degree of nuclear pleomorphism (Fig. 2A).A mitotic count was 1 to 2 per 10 high power fields (HPFs).There was no necrosis or multinucleated giant cells in the numerous sections.The spindle cells were found to be positive for s α-smooth muscle actin (Fig. 2B) and negative for desmin, S-100 protein, epithelial membrane antigen and CD34 on immunohistochemistry. Ki-67 labeling index was at 10%.Ultrathin section shows oval and spindle cells having scant cytoplasm.The tumor cells showing scant organelles except dilated rough endoplasmic reticulum.There are primitive intercellular junctions with cytoplasmic dense bodies (Fig. 3).All of features were consistent with a LGMS.After confirmed a diagnosis, we performed a brain magnetic resonance image (MRI) for finding a possible remnant tumor.T1 weighted image (T1WI) axial brain MRI showed iso-signal intensity remnant mass in right parietal Low Grade Myofibroblastic Sarcoma Occurred in the Scalp