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a 57-year - old female patient came to the hospital with pain in both thighs , especially on the right side .
the pain was exacerbated during weight bearing and walking and decreased while resting . in the physical examination ,
the range of motion of the hip joint was normal , and there were no abnormal neurological findings . on the simple radiographic inspection ,
the cortical bone of the right proximal femur was thinned and showed cystic change . decreased bone density was also observed and the trabecular bone of the overall femur was thinned ( fig .
1a ) . the magnetic resonance imaging ( mri ) was performed on the part showing cystic bone change to determine the bone tumor .
1c ) were observed in the proximal femur on both sides and in the right pubis .
an additional blood test was conducted and serum intact parathyroid hormone was 2,720 pg / ml ( normal , 15 - 65 pg / ml ) , alkaline phosphatase was 2,417 u / l ( normal , 104 - 338 u / l ) , calcium was 14.5 mg / dl ( normal , 8.6 - 10.4 mg / dl ) , and phosphate was 2.0 mg / dl ( normal , 2.6 - 4.4 mg / dl ) . to find out the cause of hyperparathyroidism , we did the ultrasonography of the thyroid .
since a nodule was observed in the left lobe of the parathyroid , fine needle aspiration was performed to obtain pathological results from the parathyroid .
furthermore as malignant change could not be excluded with the presence of a relatively large nodule , a parathyroidectomy was decided . on the 14th day from admission , the day for parathyroidectomy ,
the patient felt sudden pain in the right thigh while getting up from a bed to sit down in the morning , and radiographic inspection was performed . in the femur anteroposterior and lateral images ,
a pathological fracture was confirmed in a site where the brown tumor had formed ( fig .
2 ) . closed reduction and internal fixation with the intramedullary nailing was performed in orthopaedic surgery department , and a biopsy was conducted using specimen tissue obtained during the medullary reaming . and the additional biopsy was performed along with the parathyroidectomy in the head and neck surgery department .
the blood calcium concentration decreased to 10.0 mg / dl after the surgery , and the blood parathyroid hormone concentration became normalized after a month ( table 1 ) . in a biopsy on the femoral lesion , brown tumor was diagnosed .
four months after the surgery , the union of the fracture was confirmed ( fig .
the patient became capable of walking without a crutch or walkers by a follow - up ten months after the surgery .
an increase of blood parathyroid hormone concentration due to hyperparathyroidism destroys the balance of osteoblasts and osteoclasts through activation of the osteoclast . as a result
, bleeding and repetitive granulation of tissue partially develops in the bone , which is gradually filled with fibrous tissues which are rapidly proliferate .
these changes of bone are observed in approximately 10% to 20% of patients with hyperparathyroidism and are referred as brown tumor35 ) .
a cyst formed by the osteoclast function has clinical significance , as it increases pain and the risk of fracture . in radiological aspects ,
the difference is that it does not invade adjacent tissues and does not induce changes around the periosteum124 ) . in our case
, an osteolytic lesion in the proximal part of the right femur was observed in simple x - ray .
the cortical bone was thinned to approximately one - third the thickness of other parts of the bone .
multiple osteolytic lesions existed not only in the right proximal femur but also in the right acetabulum and left pubis . however , a periosteal reaction , which is frequently observed in cases of metastatic tumor , was not observed . with a high concentration of blood parathyroid hormone ,
as it was reported that osteolytic lesions caused by brown tumor are recovered when hyperparathyroidism is treated13 ) , we decided to treat the hyperparathyroidism for the first , including a parathyroidectomy , instead of doing surgical therapy on the bone lesion .
however , in this case , a fracture in the right femur occurred unfortunately without any trauma while the patient was bending her legs to sit up on a bed .
although she had mild pain , her bony lesion was located in a subtrochanteric site , and it showed severe cystic and osteolytic changes .
the patient 's mirels score , which indicates the possibility of a pathological fracture development , was ten ( table 2)78 ) .
as we thought that recovery of bone lesions can be expected with therapy for hyperparathyroidism without prophylactic internal fixation so we did not undergo primary stabilization with intramedullary nail at first time . but through this case , it is assumed that it will still be necessary to actively do the preventive fixation by applying the mirels score , as brown tumor is in lower extremities which is the weight bearing portion and could easily induce pathological fracture . in our case , there were other bone lesions except the right femur lesion . through the treatment for hyperparathyroidism ,
her pain on groin and left thigh region were relieved clinically and osteolytic bony changes in pubis and left proximal femur were recoverd by the follow up x - ray after ten months from the diagnosis ( fig .
the blood parathyroid hormone and calcium concentration were normalized within a few days after the parathyroidectomy . in conclusion , as brown tumor due to hyperparathyroidism has a characteristic of multiple osteolytic lesions , if there were multiple osteolytic lesions in plain x - ray film , hematological tests including blood calcium and parathyroid hormone concentration are required for differential diagnosis .
when a brown tumor does not accompany the pathological fracture , conservative treatment should be considered first .
however , we believe that it will be necessary to prophylactic internal fixation according to the mirels score in case of a high risk of fracture , as in our case .
brown tumor refers to a change of skeletones that develops as a complication of hyperparathyroidism . 
 as osteoclast is activated to stimulate reabsorption and fibrosis of bone , it causes a cystic change of the bone . 
 parathyroid carcinoma is being reported as a tumor that induces primary hyperparathyroidism . 
 it causes excessive secretion of the parathyroid hormone and increases the blood parathyroid hormone and calcium . 
 bone deformation due to brown tumor is known to be naturally recovered through the treatment for hyperparathyroidism . however , there is no clearly defined treatment for lesions that can induce pathological fractures developing in lower extremities . 
 we experienced a case where brown tumor developed in the proximal femur of a 57-year - old female patient due to parathyroid carcinoma . in this case , spontaneous fracture occurred without any trauma , and it was cured by performing intramedullary nailing fixation and parathyroidectomy . 
 we report the treatment results along with a literature review .