leiomyoma is benign smooth - muscle tumor most commonly arising in the uterus , the gastrointestinal tract , and the skin . it is usually presented by a gradually increasing pain with nonspecific radiological findings , and could be a differential diagnosis for wide range of bone tumors . we report a case of a 73-year - old japanese female patient with a painful intraosseous leiomyoma involving the proximal tibia . the patient had undergone tumor excision with wide margin , immediate weight bearing was allowed , pain had been relieved and the patient was satisfied with no recurrence , malignant change , distant metastases or functional impairment . diagnosis of intraosseous leiomyoma of the extremities is difficult due to extreme rarity of the tumor and absence of pathognomonic radiological sign in x - ray , cat , or even mri . while the exact diagnosis is only achieved by histopathological examination and with immunohistochemistry stains , which can differentiate it from malignancy , especially from the much less rare leiomyosarcoma . orthopedic oncologists have to include this rare benign tumor in the differential diagnosis of any intraosseous lesion with gradually worsening and long - standing pain , despite of benign imaging characters . different histological patterns of leiomyoma do exist , however there is no difference in prognosis or treatment options . internal fixation may be necessary if the bone defect is large or there is thinning out of the cortex that may lead to pathological fracture . leiomyoma is a benign smooth - muscle tumor that most commonly arises in the uterus , the gastrointestinaltract , and the skin . it constitutes 70% to 80% of all benign mesenchymal tumors , with uterine leiomyomata being the most common smooth - muscle tumor in women . leiomyomata are infrequently seen in the extremities and rarely seen in bone . to the best of our knowledge , five cases were intraosseous lesion in long bones , including neck of the femur , ulna , fibula , tibia   and distal femur . in addition to three cases of intraosseous leiomyomatosis secondary to disseminated leiomyomatosis have been reported . we describe a case of a patient with painful intraosseous leiomyoma involving the proximal aspect of the tibia and review the literature about intraosseous leiomyoma . a 73-year - old female presented with a four year history of a painful swelling in the left knee that was slowly growing , with a gradual increase in pain at the same time .. she had unnoticeable medical history . pain was aggravated by weight bearing , sitting straight , but she enjoyed full range of motion , and her general health was not affected . osteoarthritis of left knee joint was suspected in another clinic , and she was treated conservatively with analgesic drugs . the pain persisted despite administration of nonsteroidal anti - inflammatory drugs ( nsaids ) for long time ; she visited our outpatient clinic for consultation . clinical examination revealed local tenderness over medial aspect of proximal tibia , small well defined swelling over the medial proximal tibia was palpable . roentgenography revealed a small well - defined osteolytic lesion with thinning out of the cortex over medial part of proximal tibia , surrounded by a thin sclerotic margin ( fig . computed tomography ( ct ) scan revealed radiolucent lesion eroding the cortex , with central calcification ( fig . 1c,1d ) . magnetic resonance imaging ( mri ) revealed a hypoechoic mass in both t1and t2 weighed mages , not suppressed on t2 fat suppression view t2fs , no fluid - fluid level , it was enhanced with gadolinium , the lesion had extra osseous extension ( fig . ct - guided biopsy was performed , and the pathology showed a picture of leiomyoma , consisting of moderate cellular proliferation of smooth - muscle cells with little cellular pleomorphism , with no mitoses or necrosis . since the definite diagnosis was established , surgical excision with wide margin was decided to avoid local recurrence . the specimen consisted of gray - white soft tissue mass without apparent central necrosis or fluid content by macroscopic examination . microscopically , the tumor composed of fascicles of spindle- shaped cells with elongated nuclei and fusiformor blunt ends . otherwise , the histological exams were compatible with the results of biopsy and confirmed the diagnosis of intraosseous leiomyoma . the patient symptoms had improved after surgery , pain gradually improved postoperatively until it disappeared by two months after surgery , weight bearing was allowed from next postoperative day , convalescence passed uneventfully . at the latest follow - up after 18 months following surgery , the range of motion of left knee achieved full extension and flexion to 130 degrees without discomfort without any instability or residual pain of the knee . . a : ap view of the knee joint , showing the lesion occupying upper medial part of tibial metaphysis . b : lateral view of the knee joint , showing the lesion occupying upper medial part of tibial metaphysis . c : cat scan coronal cut view , showing the lesion eroding the bone with rim of sclerosis . d : cat scan coronal cut view , showing the lesion eroding the bone with rim of sclerosis with central calcification . a : t1 weighed image , sagittal plane , showing hypo echoic lesion with extra osseous extension b : t2 weighed image , sagittal plane , showing hypo echoic lesion with extra osseous extension c : t fat suppression weighed image , sagittal plane , showing hypo echoic lesion with extra osseous extension , the lesion lacks suppression . a : intraoperative photo showing the mass extruding from the anteromedial surface of the tibia . c : microscopic picture of the lesion with spindle cells , low cellularity and smooth muscle stroma . first case of intraosseous leiomyoma was in the maxillary tooth socket and it was described in 1976 by rhatigan and kim . the lesion is recorded in other areas of axial skeleton such as skull , spine , as well as a single case of the rib has been reported , while only limited cases of intraosseous leiomyomata in peripheral skeleton have been published . in published english literature , average age for the reported cases including our case was 44.5y10y , 4male representing 33.3% and 8 female representing 66.6% , with range between 37 - 73years ; our case is the oldest , at 73years , among all reported cases of intraosseous leiomyoma . bone predilection was noticed among the reported cases , as in six out of twelve cases the lesion was in the tibia 50% , two cases of femur 16.6% , two cases in the pelvic bone 16.6% , one case of fibula ( 8.3% ) and ulna ( 8.3% ) each . another trend that deserves attention is location of tumor within the bone ; we noticed that primary intraosseous leiomyomata of peripheral skeleton seem to arise from epi - metaphyseal region , while four cases were in the distal epi- metaphysis , three were in the proximal metaphysis , three cases with periosteal located lesion at diaphyseal level , one case in the pubic bone and another case was in in the iliac crest table ( 1 ) . summary of all reported cases of intraosseousleiomyomata diagnosis of this tumor as well as of the previous reported cases was not straightforward , it included many differential diagnoses , nopathognomonic clinical sign was related to intraosseous leiomyoma though nonspecific pain is the main presentation of intraosseous leiomyoma . swelling and difficult weight bearing are also less frequent complaints . radiographic differential diagnosis includes a variety of benign primary bone tumors , i.e. osteoid osteoma , non - ossifying fibroma , hemangioma , adamantinoma in addition to malignant tumors such as leiomyosarcoma , and metastasis . in osteoid osteoma , there is little sclerosis surrounding a central calcified nidus which is also surrounded by new bone formation . cat scan clearly reveals the nidus in most cases though it might be easily missed in mri which usually reveals bone marrow edema . in non - ossifying fibroma , the lesion is typically sharply demarcated , asymmetrical , cortically based lucency with a thin sclerotic rim . as the patient ages it seems as if it migrates away from the physis , there is no associated periosteal reaction , cortical breach or associated soft tissue mass . on mri appearances are variable , and depend on when along the development and healing phase the lesion is imaged . initially the lesion has high or intermediate t2 signal with a peripheral low signal rim corresponding to the sclerotic border as it matures and begins to ossify , the signal becomes low on all sequences , and contrast enhancement is also variable . in surface hemangiomas , it could be associated with cortical thickening , cortical erosion , and a lytic focus resembling a nidus on ct . a soft tissue mass extending from the cortex might be seen but is an infrequent finding . in adamantinoma which was included in differential diagnosis because of the tibial location of the lesion , it appears as a multi- locular or slightly expansible osteolytic lesion . lesions tend to have an eccentric epicenter and a lack of periosteal reaction . there may be a locally aggressive disease at presentation . on mri , it might be presented as one of two morphologic patterns either a solitary lobulated focus or multiple small nodules in one or more foci . in leiomyosarcoma , radiological feature depends on grade of malignancy , in high grade leiomyosarcomas there is ill- defined , irregular osteolytic lesion with a moth - eaten or permeative pattern of osseous destruction radiographically , and diffuse involvement and destruction of the medullary bone histologically . on the other hand , low grade tumors exhibit diffuse involvement of the marrow spaces , and have radiographic features , including a geographic pattern of bone destruction and a sclerotic rim . the lesion appears so intense to muscle t1 , while int2 intermediate to hypo intense to neighboring fat , and predominantly hyper intense in t2fs . metastasis is not a far possibility , it would occur from primary carcinomas , including lung , breast , kidney , and pancreas . the thin capsule seen around the lesion , as well as its oval shape and sharply marginated edge made metastasis less likely . we considered adamantinoma far less likely in the differential diagnosis , as histologically this neoplasm is noted for its heterogeneity and presence of epithelial islands . a malignant spindle cell tumor was not considered because the tumor lacked pleomorphism , high rate of mitoses , and necrosis . the sclerotic margins seen on the conventional radiograph and in the histologic sections also supported the benign nature of this tumor . however , absence of signs of malignancy must be carefully documented in order to rule out leiomyosarcoma . histologically ; leiomyoma is classified into three histological categories : solid leiomyoma , vascular leiomyoma ( or angioleiomyoma ) , and epithelioid leiomyoma . while angioleiomyoma is the most prevalent type in soft tissues , solid leiomyoma represents the majority of cases of intraosseous leiomyomata , it exhibits the same histological features as leiomyoma at other sites . it is composed of a proliferation of spindle - shaped cells arranged in thick intersecting bundles . mitoses are very rarely seen ( low rate of mitosis 0 - 4per ten high power fields ) with moderate cellularity and no necrosis . angioleiomyomas are further classified into three histological categories : solid ( the most common type in soft tissues ) , venous , and cavernous . however , all three patterns are often present within the same tumor . similarly , reported cases of intraosseous angioleiomyoma showed no distinctive histological features compared to soft - tissue angioleiomyomas . in published cases , three cases out of eleven were histologically angioleiomyoma , two were in tibia and one in the iliac bone . . a : anteroposterior view of the knee joint , showing the filled bone defect in the upper medial part of tibial metaphysis b : lateral view of the knee joint , showing the filled bone defect in the upper medial part of tibial metaphysis the use of immunohistochemical staining was helpful in this case , the tumor cells stained strongly for muscle markers , including smooth muscle actin and desmin , thus confirming this tumor s smooth muscle origin . the neoplastic cells did not stain for neural , fibrous , or epithelial markers ( s-100 , cd34 , and ae1/3 , respectively ) . the standard treatment for intraosseous leiomyoma is extensive tumor excision with wide margin followed by packing of the cavity with autologous cancellous bone graft . till now , no cases of recurrences have been reported after complete excision , however , regular follow - up is necessary to observe the risk of recurrence . in only one of the previously reported cases , reconstruction using bone graft alone was not enough , and reconstruction by tka was performed due to difficulty in preserving the articular cartilage and thinning out of the bone . otherwise , all known cases were treated either by en - bloc excision , surgical resection or curettage . in addition to bone graft , and in all cases , results were satisfactory to excellent with no recurrence , malignant change , or distant metastases , early recovery and restoration of function . in our case , we performed wide tumor excision , the bone defect was not large enough to necessitate internal fixation . patient satisfaction after surgery was good , with improvement of pain , and preserved function of the knee . there was no recurrence , malignant change or distant metastases at the latest follow up visits . diagnosis of intraosseous leiomyoma of the extremities is difficult due to extreme rarity of the tumor and absence of pathognomonic radiological signs in x - ray , cat , or even mri . the exact diagnosis is only achieved by histopathological examination and with immunohistochemistry stains , which can differentiate it from malignancy , especially from the much less rare leiomyosarcoma . orthopedic oncologists have to include this rare benign tumor in the differential diagnosis of any intraosseous lesion with gradually worsening and long - standing pain , despite of benign imaging characters . different histological patterns of leiomyoma do exist , however there is no difference in prognosis or treatment options . internal fixation may be necessary if the bone defect is large or there is thinning out of the cortex which may lead to pathological fracture . intraosseous leiomyoma is a rare tumor ; it lacks a pathognomonic radiological sign which makes its diagnosis quite difficult . it is better to include this tumor in the differential diagnosis of painful benign intraosseous lesions .
introduction : leiomyoma is benign smooth - muscle tumor most commonly arising in the uterus , the gastrointestinal tract , and the skin . leiomyomata are infrequently seen in the extremities and rarely seen in the bone . 
 it is usually presented by a gradually increasing pain with nonspecific radiological findings , and could be a differential diagnosis for wide range of bone tumors.case presentation : we report a case of a 73-year - old japanese female patient with a painful intraosseous leiomyoma involving the proximal tibia . 
 the patient had undergone tumor excision with wide margin , immediate weight bearing was allowed , pain had been relieved and the patient was satisfied with no recurrence , malignant change , distant metastases or functional impairment . 
 we reviewed all published cases of intraosseous leiomyomata in english literature.conclusion:diagnosis of intraosseous leiomyoma of the extremities is difficult due to extreme rarity of the tumor and absence of pathognomonic radiological sign in x - ray , cat , or even mri . while the exact diagnosis is only achieved by histopathological examination and with immunohistochemistry stains , which can differentiate it from malignancy , especially from the much less rare leiomyosarcoma . 
 orthopedic oncologists have to include this rare benign tumor in the differential diagnosis of any intraosseous lesion with gradually worsening and long - standing pain , despite of benign imaging characters . 
 different histological patterns of leiomyoma do exist , however there is no difference in prognosis or treatment options . 
 treatment standard includes wide excision with autologous bone graft whenever possible . 
 internal fixation may be necessary if the bone defect is large or there is thinning out of the cortex that may lead to pathological fracture .