myofibroblasts are spindle mesenchymal cells sharing features of both muscular and fibroblastic cells6 ) and represent a connective tissue cell characterized by morphologic and functional properties intermediate between fibroblasts and smooth muscle cells3 ) . low - grade myofibroblastic sarcoma ( lgms ) represents a distinct atypical myofibroblastic tumor with fibromatosis like features and has a predilection for the head and neck , particularly the tongue and oral cavity28 ) . more than 80% of malignant tumors of the head - and - neck region originate from squamous epithelium . therefore , the incidence of mesenchymal tumors is low . among them , myofibroblastic sarcomas are extremely rare712 ) . jay et al.5 ) reviewed in the literature that reported 22 cases ( including their cases ) myofibroblastic sarcomas in the oral cavity and maxillofacial region . among them , 6 cases occur in tongue . five ( 24% ) cases showed local recurrence and one case distant metastases during follow up period . we describe a case of lgms occurring in the scalp of a 26-year - old man and review this rare entity tumor in the literatures . a 26-year - old man presented with a 12-month history of a slow growing palpable hard mass in the right parietal scalp . enhanced computed tomography ( ct ) scanning of head showed a well - defined and heterogeneously enhancing scalp mass ( fig . a mitotic count was 1 to 2 per 10 high power fields ( hpfs ) . the spindle cells were found to be positive for s -smooth muscle actin ( fig . 2b ) and negative for desmin , s-100 protein , epithelial membrane antigen and cd34 on immunohistochemistry . 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 scalp ( fig . gadolinium enhancement t1wi axial brain mri showed the heterogeneously enhancing mass , which was measured 0.31 cm ( fig . after 14 months of surgery , follow up brain mri showed no evidence of recurred lesion in scalp ( fig . lgms is a recently defined tumor that can be considered a part of the spectrum of malignant mesenchymal tumors , showing features of myofibroblastic differentiation11 ) . myofibroblasts have been recognized for over three decades , but the existence of sarcomas composed of myofibroblasts has become generally accepted recently8 ) . myofibroblastic sarcoma must be distinguished from other neoplasms , which including nodular fasciitis , proliferative myositis and fibromatosis , and also other types of low - grade spindle - cell sarcomas , leiomyosarcoma and fibrosarcoma10 ) . mentzel et al.7 ) characterized myofibrosarcoma or myofibroblastic sarcoma as a spindle cell sarcoma composed of myofibroblasts . they summarized clinical findings of lgms patients , which data show that the age of the patients ranged between 19 and 72 years ( median : 42 years ) . the diagnosis of lgms is made on the basis of ultrastructual findings as determined by light microscopy and immunocytochemistry . lgms have a mild to moderate amount of eosinophilic or amphophilic cytoplasm and fusiform nuclei , and usually characterized with mild nuclear pleomorphism and low mitotic rate ( 1 - 6/10 hpfs)12 ) . our case shows 1 to 2 per 10 hpfs of mitotic rate and moderate pleomorphism of spindle cells . lgms tumors cells express strong positive immunoreactivity for at least one of following myogenic markers that muscle - specific actin ( hhf35 ) , -smooth muscle actin , rarely desmin1781112 ) . the tumors do not stain for s-100 protein , epithelial markers such as laminin and h - caldesmon4812 ) . lgms usually affects deep soft tissue sites and is more often poorly circumscribed with fascicles and individual cells infiltrating between muscle fibers , although focal circumscription is not unusual45 ) . the treatment of this rare tumor should include a simple local excision with wide surgical margins and adjuvant therapies such as chemotherapy or radiotherapy have also been used in some cases91112 ) . follow - up information is limited in the literature , but multiple soft tissues , bone , and pulmonary metastases from a chest wall mass were reported5 ) . therefore , lgms are needed years of clinical follow - up evaluation including scans11 ) . we report of the case of lgms occurred in the scalp . because of the rarity of this sarcoma types , its biological behavior and proper treatment are still unclear . however , lgms can be best managed with wide surgical resection and regular follow - up .
low - grade myofibroblastic sarcoma ( lgms ) is a rare sarcoma with myofibroblastic differentiation . 
 lgms has a propensity for local recurrence and is associated with a low risk of metastatic spread . a 26-year - old man presented with a 12-month history of a slow growing palpable hard mass in the right parietal scalp . 
 enhanced ct scan of head showed a 34 cm sized well - defined and heterogeneously enhancing scalp mass . 
 the patient underwent excision of the tumor . 
 the histological and immunohistochemical features were consistent with a lgms . 
 we performed re - operation for remnant tumor removal after diagnosis . 
 after 14 months of surgery , the patient was well - being state .