Life Expectancy Is Poor in Patients with Diffuse Idiopathic Skeletal Hyperostosis-Related Pyogenic Vertebral Osteomyelitis.

Introduction: Pyogenic vertebral osteomyelitis (PVO) is an uncommon but life-threatening infectious disease. Diffuse idiopathic skeletal hyperostosis (DISH) is an age-related disorder and sometimes problematic in terms of spinal instability or high mortality, especially in cases of DISH-related fracture. Meanwhile, no reports have focused on the impact of DISH on the clinical outcomes after treatment for PVO. We hypothesized that PVO occurring at DISH-related segments might contribute to poor clinical results or high mortality rates. The purpose of this study was to investigate the impact of DISH on mortality after treatment for PVO in a retrospective cohort study. Methods: This study involved patients who were hospitalized and treated for PVO at a single institution. DISH-related PVO was defined as PVO within a segment ossified by DISH or PVO at the neighboring intervertebral level of the segment ossified by DISH. Differences in mortality between patients with DISH-related and non-DISH-related PVO were investigated. Results: This study included 55 patients. DISH-related PVO was observed in 13 patients. The mortality rate was significantly higher in patients with DISH-related PVO than in those with non-DISH-related PVO (62% and 23%, respectively; p=0.016). Propensity score-adjusted analysis showed that DISH-related PVO was an independent risk factor for mortality (adjusted hazard ratio, 2.79; p=0.034). The survival probability was significantly shorter in patients with DISH-related PVO than in those with non-DISH-related PVO (p=0.006). PVO in which the intravertebral body was the center of involvement was significantly more common in DISH-related PVO than in non-DISH-related PVO (38% and 5%, respectively; p=0.006). Conclusions: DISH-related PVO was associated with a higher mortality rate and shorter life expectancy than non-DISH-related PVO. Similar to advanced age, PVO at the segment ossified by DISH should be recognized as a risk factor for mortality when choosing the optimal treatment strategy.

Prediction of the future leg length after rotationplasty in a 3-year-old boy with extraskeletal Ewing sarcoma and long follow-up until skeletal maturity: a case report.

Rotationplasty is a useful option for limb salvage surgery in pediatric patients with malignant bone and soft tissue tumors. However, bone growth after rotationplasty remains poorly characterized. We present a case of a 3-year-old boy with extraskeletal Ewing sarcoma who underwent multidrug chemotherapy (vincristine, doxorubicin, ifosfamide and etoposide), wide resection and functional reconstruction with rotationplasty. No radiotherapy was administered during the treatment course and the patient has been followed up for 16 years after rotationplasty. Leg length at skeletal maturity was predicted using postoperative radiograph measurements of the affected leg at the age of 4 years. Two conventional prediction methods, the multiplier and straight-line graph methods were used for prediction. The predicted leg length was compared with the actual leg length to assess bone growth after rotationplasty. Immediately after surgery, the lengths of the affected lower leg, femur and tibia were 32.5, 15.0 and 17.6 cm, respectively, and the predicted leg length of the affected leg at skeletal maturity using the multiplier and straight-line graph methods was 44.6 and 44.2 cm, respectively. However, the actual length of the affected leg at skeletal maturity was 49.8 cm, and the gap between actual and predicted lengths was more than 5 cm. In conclusion, the affected leg after rotationplasty showed more than expected bone overgrowth compared with the predictions of the conventional methods.

Possible pathogenesis of calcaneal bone cysts.

INTRODUCTION: Recent literature indicates that calcaneal bone cysts have different clinical features compared to long bone cysts. Yet, previous studies have mainly focused on pathogenesis of long bone cysts. In this study, the pathogenesis of calcaneal bone cysts was investigated from radiological and pathological findings. MATERIALS AND METHODS: Patients comprised 18 males and 6 females diagnosed with calcaneal bone cysts at a median age ± standard deviation of 13.0 ± 3.6 years. Plain radiographs, computed tomography, magnetic resonance imaging, cystography, bone scintigraphy, and pathology were reviewed. RESULTS: All cysts occupied the central triangular area of the bone, with six extending posteriorly and two developing anteriorly. Fifteen of 20 cases (75%) showed the expanded foramen structures at the anterior margin of the posterior facet. According to cystography, four cysts showed absence of leakage to subtalar joint. Cystic fluid caused chronic haemorrhaging in 18 cases and pathologically detected cholesterol clefts were noted in 14 cases. DISCUSSION: The location of the expanded foramen structures was consistent with the nutrient foramens of the sinus tarsi artery in the unaffected population. Hence, initial cysts may originate from the collapse of the sinus tarsi artery. Subsequent haemorrhage may extend into the central triangle area, which is biomechanically free of stress. Because of poor bone remodelling, degenerative change of the haemorrhage is prolonged. The results of this study showed that circulation collapse of the sinus tarsi artery and mechanical factors are important in the formation of calcaneal bone cysts.

Clinical course of soft tissue sarcomas presenting as malignant wounds.

BACKGROUND: Soft tissue sarcomas can invade the skin and occasionally present as malignant wounds characterized by bleeding, exudate, odor, and infection. This study aimed to highlight the clinical problems associated with sarcomas with malignant wounds. METHODS: The patient group comprised 12 males and 1 female, with a median age at diagnosis of 75 (range 23-95) years old. The average follow-up was 28.3 months. Clinical information concerning the patients with soft tissue sarcomas presenting as malignant wounds was retrospectively investigated. RESULTS: Eleven out of 13 malignant wounds cases were male and over 65 years old. Tumors were located in the chest wall in 4 patients and the thigh in 4, respectively. The histology was high-grade in 12 patients. Persistent bleeding from malignant wounds was observed in 6 patients. The patients' pre-operative hemoglobin level was 7.5 ± 1.9 g/dl. For the purpose of temporary hemostasis, Mohs' paste was applied in 1 case and zinc oxide starch was applied in 3. Surgical removal was done in 10 patients, and amputation in 2. Six patients needed skin reconstruction. Post-operative surgical site infection was found in 5 patients, but the infection did not occur in the patients who underwent skin reconstruction of musculocutaneous flaps. The 5-year survival rate was 25.4%. CONCLUSIONS: Massive bleeding from the tumor impairs patients' quality of life and can be life-threatening. To avoid exacerbating the systemic condition of elderly cancer patients, urgent surgical removal is recommended, especially in cases of exposed tumors with persistent bleeding. Orthopedic oncologists should be aware of surgical site infection as a potential post-operative complication.

Lymphoproliferative disorder with pathological fracture of the femur in a patient with rheumatoid arthritis treated with methotrexate: A case report.

Methotrexate (MTX) is the key drug for the treatment of rheumatoid arthritis (RA). MTX-treated RA has been associated with the development of lymphoproliferative disorders (LPDs). Notably, the hyperimmune state of RA itself or the immunosuppressive state induced by MTX administration may contribute to development of LPD. Furthermore, Epstein-Barr virus (EBV) has been indicated to contribute to the development of MTX-LPD. MTX-associated LPD (MTX-LPD) may affect nodal or extranodal sites, including the gastrointestinal tract, skin, lungs, kidneys, and soft tissues, at an almost equal frequency. However, it is rare for MTX-LPD to manifest as multiple bone tumors with a pathological fracture. The present study reported the case of a 46-year-old Japanese woman with RA who had complications of EBV-positive MTX-LPD during an approximate 5-year course of MTX therapy. The present study indicated a rare case in which the LPD had spread to multiple bones in a patient with a pathologic fracture. Notably, the LPD was subclassified as diffuse large B-cell lymphoma (DLBCL).

An unusual presentation of pneumothorax associated with cystic lung metastasis from epithelioid sarcoma: A case report and review of the literature.

Circumscribed solid nodules are common in pulmonary metastases from sarcoma, but cystic pulmonary metastases from sarcomas are extremely rare. An unusual case of a 33-year-old man presenting with left spontaneous pneumothorax in association with cystic pulmonary metastases from an epithelioid sarcoma in the left forearm was discussed in the present study. The patient underwent wide resection of an epithelioid sarcoma in the left forearm 6 years prior. Periodical computed tomography revealed a gradual increase in the number and size of bilateral multiple cystic pulmonary metastases despite repeated chemotherapy treatment. At 33 years of age, the patient visited the outpatient department for sudden left chest pain and dyspnea. Plain radiography demonstrated spontaneous pneumothorax in the left lung; chest tube insertion and pleurodesis were successfully performed thereafter. At the last follow-up, 24 months after spontaneous pneumothorax, he is still alive and receiving chemotherapy treatment. Spontaneous pneumothorax is a common complication associated with cystic pulmonary metastases from epithelioid sarcoma. Orthopedic oncologists need to be aware of this unusual sarcomatous metastasis during the follow-up of advanced epithelioid sarcoma.

Diagnostic value of tumor-fascia relationship in superficial soft tissue masses on magnetic resonance imaging.

PURPOSE: Many surgeons participate in the management of superficial soft tissue masses, and a preoperative incorrect diagnosis frequently results in dismal oncological outcomes. The aim of this study was to identify distinguishing magnetic resonance imaging features between malignant and non-malignant lesions. METHODS: The clinicopathological data for 219 patients (men 114; women 105) with superficial soft tissue masses treated from January 2007 to December 2016 in our institution were retrospectively analyzed. The median age at the first visit was 55.6 years (range 1-90 years). MRI findings of tumor size, margin, lobulation, intratumoral hemorrhage, peritumoral edema, and tumor-fascia relationship were compared with the final histological diagnosis and tumor grade. RESULTS: Univariate analysis revealed significant relationships between histologically malignant lesions and tumor size ≥5 cm (p = 0.035), positive peritumoral edema (p = 0.031), and tumor-fascia relationship (p<0.001), but not margin (p = 0.107), lobulation (p = 0.071), and intratumoral hemorrhage (p = 0.17). In addition, using multivariate analysis, the tumor-fascia relationship (p<0.001) and tumor size were significant factors. A significant correlation between tumor-fascia relationship and malignancy (p<0.001) was observed; such a relationship was, however, not observed for tumor grade (p = 0.43). CONCLUSIONS: Tumors measuring ≥5 cm and the tumor-fascia relationship on magnetic resonance imaging are highly indicative of malignancy. When superficial soft tissue masses cross the superficial fascia and form obtuse angles with the fascia, sarcoma should be considered. The tumor-fascia relationship can offer surgeons useful information regarding the status of superficial soft tissue masses.

Clinical features of soft tissue sarcoma presenting intra-tumour haematoma: case series and review of the literature.

INTRODUCTION: Intra-tumour haematoma is an uncommon clinical presentation in malignant soft tissue tumours. This study aimed to highlight the clinical features of patients with soft tissue sarcomas with intra-tumour haematoma. METHODS: The patient group was composed of eight men and one woman aged between 29 and 83 years (mean 44.0 ± 20.8). The average follow-up was 29.8 months. Clinical information, including clinical features, radiological information and treatment course, was retrospectively investigated. RESULTS: Tumours were predominantly located in the chest wall and thigh, and average diameter was 10.3 cm. Six patients underwent needle biopsy with ultrasound sonography, and three underwent an open biopsy. Histological diagnoses indicated that all tumours were high grade, three of which were undifferentiated pleomorphic sarcomas, three synovial sarcomas, two pleomorphic liposarcomas, one a leiomyosarcoma and one a malignant peripheral nerve sheath tumour. The median diagnostic delay time was 3.0 months. Magnetic resonance imaging (MRI) indicated a haematoma area <25 % in three, 25-50 % in four and 50 % two. A wide resection was performed in eight patients, and radiotherapy was administered to one patient for the initial local treatment of a primary tumour. Local recurrence was detected in four patients, whilst five developed lung metastases. The five-year survival rate was 57.1 % and median survival 34.0 months. CONCLUSIONS: Soft tissue sarcomas with intra-tumour haematoma presented with locally aggressive and highly metastatic behavior, consistent with high-grade tumours.

Prognostic factors for elderly patients with primary malignant bone and soft tissue tumors.

The number of patients with primary malignant bone and soft tissue tumors in Japan is increasing in line with the increasing size of the elderly population. The aim of the present study was to determine the prognostic factors of primary malignant bone or soft tissue tumors in elderly patients. Clinical data was obtained from 90 patients, aged ≥65 years, with primary malignant bone or soft tissue tumors (bone, 20 cases; and soft tissue, 70 cases), treated at the Osaka City University Hospital between 1993 and 2013. Clinical information prior to treatment and tumor type, location, size, depth, grade and American Society of Anesthesiologists-Physical Status (ASA-PS) score were evaluated in order to identify prognostic factors using the Cox proportional hazards regression model. In addition, 5-year survival rates were evaluated using the Kaplan-Meier method. The average follow-up period was 44.8 months and the 5-year overall survival rate was 77.5%. In the multivariate analysis, ASA-PS score and high-grade sarcoma were found to be associated with a poorer overall survival. No significant differences were observed between the patient group aged 65-74 years and that aged ≥75 years. In general, aging is associated with physically reduced function and an increased prevalence of comorbidities. It was therefore expected that increasing age may be a predictive factor for poor prognosis. However, the results of the present study suggested that ASA-PS score and tumor grade were significant factors associated with poor prognosis, whereas increasing age was not. Therefore, the treatment of elderly patients with primary bone and soft tissue tumors should not be based on age.

Fertility following treatment of high-grade malignant bone and soft tissue tumors in young adults.

This study was conducted to investigate marriage and fertility in long-term survivors with high-grade bone and soft tissue tumors following chemotherapy. We reviewed issues related to fertility in 47 patients (24 men and 23 women) who had survived for >5 years. The median age at diagnosis was 18.0±8.9 years and the mean duration of follow-up 11.0 years. We investigated the proportions of married subjects (number of married/total number of subjects) and fertile subjects (number who had fathered or conceived offspring/total number of subjects), the interval between first delivery and last chemotherapy, type of delivery, congenital deformities in the offspring and the association between cumulative dose of chemotherapeutic agents and subsequent reproduction. The final proportions of married and fertile subjects following sarcoma treatment were 36.2% (17/47) and 29.8% (14/47), respectively. Two subjects had fathered and 8 had conceived a total of 15 offspring. The proportion of fertile men was significantly lower compared to that of women. The mean interval between the last chemotherapy and the first delivery was 9.5 years. Of the 10 first births, 6 were normal transvaginal deliveries and 4 were caesarean sections (1 was a medical termination due to lung metastases, 1 was due to infected amniotic fluid caused by uterine myomas and 2 were performed due to abnormal rotation of the fetus). No offspring presented with congenital deformities. Fertile men had received smaller cumulative chemotherapeutic agent doses, particularly of ifosfamide, compared to those who had not fathered any offspring. In conclusion, infertility occurs more frequently in men compared to women following intensive chemotherapy. All the patients should be offered counseling regarding the potential risk of infertility prior to cancer treatment.

Flail hip joint following periacetabular tumor resection of the pelvis using upper surface of the femoral neck as a saddle: A case report.

Reconstruction following periacetabular tumor resection of the pelvis is one of the most challenging issues in limb salvage surgery. An ideal procedure has still not been established. There are several reconstruction methods available, including arthrodesis, pseudoarthrosis, resection arthroplasty, prosthetic arthroplasty, saddle prosthesis, allograft and hip transposition. In our hospital, we have been using a flail hip joint procedure without reconstruction. Herein, we report good extremity function following a flail hip joint procedure which used the upper surface of the femoral neck as a saddle facing the remaining ilium. To the best of our knowledge, among the reported flail hip joint cases, this procedure has never been used. The patient is able to walk without any pain for several hundred meters with a shoe lift but without a cane, as observed at a 20-year follow-up. The authors consider that the flail hip joint using the upper surface of the femoral neck as a saddle is a simple and effective method.

Contrast-enhanced color Doppler ultrasonography increases diagnostic accuracy for soft tissue tumors.

Resolution of ultrasonography (US) has undergone marked development. Additionally, a new-generation contrast medium (Sonazoid) used for US is newly available. Contrast-enhanced US has been widely used for evaluating several types of cancer. In the present study, we evaluated the ability of color Doppler US (CDUS) and Sonazoid to differentiate between benign and malignant soft tissue tumors. A total of 180 patients (87 male, 93 female) were enrolled in the present study. The patient ages ranged from 1 to 91 years (mean 58.1±20.0 years). The maximum size, depth, tumor margins, shape, echogenicity and textural pattern were measured on gray-scale images. CDUS was used to evaluate the intratumoral blood flow with and without Sonazoid. Peak systolic flow velocity (Vp), mean flow velocity (Vm), resistivity index (RI) and pulsatility index (PI) of each detected intratumoral artery were automatically calculated with power Doppler US (PDUS). The present study included 118 benign and 62 malignant tumors. Statistical significances were found in size, depth, tumor margin and textural pattern but not in shape or echogenicity on gray-scale images. Before Sonazoid injection, CDUS findings showed 55% sensitivity, 77% specificity and 69% accuracy, whereas contrast-enhanced CDUS showed 87% sensitivity, 68% specificity and 74% accuracy. There were no statistically significant differences between malignant and benign tumors regarding the mean Vp, Vm, RI and PI values determined on PDUS. In conclusion, contrast-enhanced CDUS proved to be a reliable diagnostic tool for detecting malignant potential in soft tissue tumors.

Knee reconstruction with endoprosthesis after extra-articular and intra-articular resection of osteosarcoma.

OBJECTIVE: Extra-articular resection is necessary to obtain a wide margin for primary osteosarcomas invading the knee joint, and the limb is often reconstructed using a prosthesis. Here, outcomes of extra-articular and intra-articular procedures were compared. METHODS: Between 1999 and 2012, 14 patients with osteosarcoma underwent extra-articular excision (n = 6; ages 23-65 years; mean follow-up 82.8 months) or intra-articular excision (n = 8; ages 8-58 years; mean follow-up 96.4 months). In the extra-articular group, there was one Enneking Stage IIA case and five Enneking Stage IIB cases. No local recurrences were noted in either group. RESULTS: Patient outcomes were as follows (extra-articular cases vs. intra-articular cases): continuous disease-free (2 vs. 7), alive with disease (2 vs. 0) and death from disease (1 vs. 1). Average Musculoskeletal Tumor Society functional scores were 69.4% (range 63.3-83.3%) and 88.3% (range 70.0-96.7%) in the extra-articular and intra-articular groups, respectively, constituting a significant difference (P < 0.05). The 5-year oncological overall survival exceeded 80% in both groups. Amputation was necessary for one patient in the extra-articular group. The 5-year event-free prosthesis survival rates in the extra-articular and intra-articular groups were 33.3 and 75.0%, respectively (P < 0.05). CONCLUSION: The extra-articular excision group developed more complications than the intra-articular excision group, as a result of extensive bone and muscle excision. The limb survival rates were similar in both groups. Our results suggest that extra-articular resection was a necessary and clinically acceptable procedure.

Diagnosis of osteosarcoma in a patient previously treated for Ewing sarcoma.

Primary malignant bone tumors, whether Ewing sarcoma or osteosarcoma, are a rare type of tumor. The sequential occurrence of two bone sarcomas, Ewing sarcoma and high-grade osteosarcoma, in the same patient at two different locations is an exceptionally rare phenomenon. We present the case of a 13-year-old girl who presented with a high-grade osteoblastic osteosarcoma of the distal femur, 7 years after treatment for Ewing sarcoma of the left pelvis. She did not receive radiation therapy. Following the recent developing multidisciplinary therapy, long-term follow-up for monitoring latent treatment-related adverse effects may be necessary for survivors of primary malignant bone tumors.

Role of FDG-PET/CT for monitoring soft tissue tumors.

The aim of the current study was to evaluate the limitations of 2-deoxy-2-F18-fluoro-D-glucose positron emission tomography combined with computed tomography (FDG-PET/CT) when monitoring soft tissue tumors. The diagnostic criteria of malignancy was defined as the tumor having a maximum standardized uptake value (SUVmax) ≥2.0 and a maximum diameter ≥5 cm as measured using FDG-PET/CT. One-hundred-and-thirteen patients, that were either included in the criteria or not, were compared. In addition, the values of SUVmax of the primary tumor and relapse in 12 patients were evaluated. The Kaplan-Meier analysis demonstrated that patients with tumors measuring ≥5 cm size and ≥2.0 SUVmax were associated with a worse survival rate. Among the 12 patients with relapse, statistical significances were detected in the tumor diameters, however, not in the SUVmax values. Thus, the criteria identified patients that were associated with a poor prognosis, and the SUVmax of distant metastases and local recurrences were identified to be significantly affected by tumor size.

A comparative study of clinicopathological features between simple bone cysts of the calcaneus and the long bone.

BACKGROUND: The potential unrevealed clinicopathological differences between simple bone cysts situated in the calcaneus (calcaneal bone cysts) and those situated in long bones (long bone cysts) were investigated in the present study. METHODS: A total of 41 cysts from 41 patients who underwent operative treatment were evaluated: 16 cysts in the calcaneus, 17 in the humerus, 7 in the femur, and 1 in the tibia. The clinical course, radiological findings, and histological features were retrospectively reviewed. RESULTS: The mean patient age was 11.5 years (range, 3 to 25 years), and the mean follow-up was 33.0 months (range, 12 to 77 months). The mean patient age was significantly higher in patients with calcaneal bone cysts (13.5 years; long bone cysts, 10.2 years, P < .05). No treatment failure was seen for patients with calcaneal bone cysts, while 7 long bone cysts required reoperation. In H&E-stained specimens of the cyst wall, cholesterol clefts were identified in 10 of the 16 calcaneal bone cysts (62.5%), whereas none were identified in long bone cysts (0%; P < .0001). CONCLUSION: Our study elucidates the different clinicopathological features existing between calcaneal bone cysts and long bone cysts. Cholesterol clefting is most likely due to hemorrhaging and the subsequent breakdown of blood in the cyst. The significance of these differences between long bone and calcaneal cysts is still open to conjecture. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

Neoadjuvant and adjuvant chemotherapy with high-dose ifosfamide, doxorubicin, cisplatin and high-dose methotrexate in non-metastatic osteosarcoma of the extremities: a phase II trial in Japan.

From 1997 to 2003, 40 patients (all <40 years of age) with non-metastatic osteosarcoma of the extremities were treated with OOS-D and definitive surgery. Two cycles of doxorubicin 90 mg/m(2) plus cisplatin 120 mg/m(2) and ifosfamide 15 g/m(2) were given as neoadjuvant chemotherapy, and two cycles of doxorubicin/cisplatin and ifosfamide, and two cycles of high-dose methotrexate (10-12 g/m(2)) were given post-operatively. All patients underwent limb salvage surgeries, and 66% showed good response to neoadjuvant chemotherapy. With a median follow-up period of 117 months, 31 of the evaluable 40 patients were continuously disease-free, 7 were currently alive with no evidence of disease, and 2 died of disease. There was no local recurrence. The 5-year event-free and overall survival rates were 83 and 98%, respectively. The 10-year event-free and overall survival rates were 80 and 95%, respectively. The major form of toxicity was haematological one.

Prognostic factors for patients with solitary bone metastasis.

BACKGROUND: The term 'solitary bone metastasis' is defined in the present study as a single bone metastasis originating from a primary cancer without visceral organ metastasis. We assessed the survival rates and prognostic factors in 42 patients with solitary bone metastasis, and discussed the impact of different surgical strategies on survival. METHODS: We retrospectively analyzed data from 42 patients (25 male, 17 female) who underwent treatment for solitary bone metastasis at a single institution. The median age of the patients was 64.5 years (range 41-82 years). The patients were followed for an average period of 21.2 months (range 0.4-127.3 months). Their clinical records were retrospectively reviewed. Factors influencing survival were determined using univariate and multivariate analyses; particular attention was paid to the orthopedic surgery used for solitary bone metastasis. RESULTS: The 1-year survival rate was 76.5%, and the median survival period was 30.0 months. The presence of primary cancer and poor performance status were identified as independent prognostic factors using Cox regression multivariate analysis. Tumor resection and surgical margin were not significantly related to patient survival. CONCLUSIONS: The results of this analysis indicated that the prognosis for patients with solitary bone metastasis depended on the presence of primary cancer and on poor performance status.

Overexpression of hexokinase-2 in giant cell tumor of bone is associated with false positive in bone tumor on FDG-PET/CT.

INTRODUCTION: The aim of the current study was to evaluate the usefulness of maximum standardized uptake value (SUV(max)) in 2-deoxy-2-F(18)-fluoro-D-glucose positron emission tomography combined with computed tomography (18F-FDG-PET/CT) for preoperative differential diagnosis between benign and malignant bone tumors. MATERIALS AND METHODS: Seventy-nine patients with bone tumors were examined by FDG-PET prior to histopathological diagnosis. The SUV(max) was calculated and compared between benign and malignant lesions, and among different histopathological subgroups, to identify false-positive histological subtypes. RESULTS: There was a statistically significant difference in the SUV(max) of benign (3.7 ± 3.3; n = 17) and malignant (5.3 ± 3.3; n = 62) bone tumors. However, receiver operating characteristic curve analysis revealed the poor accuracy of this distinction. The cut-off value was determined to be 2.6, while the value of sensitivity and specificity was calculated to be 74.2 and 64.7 %, respectively. Giant cell tumor of bone (9.0 ± 2.0; n = 5) displayed a higher SUV(max) than osteosarcoma (4.2 ± 2.3; n = 18). Immunohistochemical analysis demonstrated that markers of these cancers, hexokinase-2 (HK-2) and glucose transporter type 1 (GLUT-1), supported our findings. CONCLUSION: The poor accuracy of SUV(max) in 18F-FDG-PET/CT in distinguishing malignant from benign bone tumors was confirmed; some benign bone tumors showed high FDG uptake. Giant cell tumor of bone was a major false-positive histopathological subtype of bone tumors, showing high FDG accumulation. HK-2 contributed significantly to FDG uptake, whereas GLUT-1 appeared to play no role in FDG uptake in giant cell tumor of bone.