Benign bone tumours in Western Australia, 1972-1996

Chondromyxoid Fibroma of the Distal Tibia: A Rare Case Report

Chondromyxoid fibroma is one of the rarest bone tumours, occurring most frequently in adult men in their second and third decades. It generally affects the metaphysis of long bones, particularly the femur and tibia. Diagnosis can pose differential challenges with various tumor types, particularly chondrosarcoma, requiring separate management. We present a case of chondromyxoid fibroma of the distal tibia detected by soft tissue swelling. Clinical, epidemiological and radiological aspects will be discussed.

Diagnosis and Literature Review of Chondromyxoid Fibroma - A Pathological Puzzle

INTRODUCTION

Chondromyxoid fibroma (CMF) is a benign rare bone tumor of slow-growing nature arising from chondroblastic derivation. CMF in most of the cases is a diagnosis of exclusion, and in this case report, we differentiate the histological and radiological findings of CMF and difficulties in diagnosis of CMF from potential differential diagnosis.

CASE REPORT

A 38-year-old female patient presented with a history of limping for 5 months and on evaluation revealed an expansile osteolytic lesion in fibular head with septations and soft tissue component. Excision biopsy was done. Histological examination revealed a cellular neoplasm arranged as vague nodules in chondroid background with occasional mitotic figures and giant cells in periphery without any calcification. To rule out chondroblastoma, S-100 and epithelial markers were done which was negative establishing diagnosis of CMF by exclusion.

CONCLUSION

CMF is often misdiagnosed being a radiological and pathological mimicker. Histology remains key to diagnosis. En bloc resection remains the mainstay of management in expendable bone-like fibula.

Incidence Trends in the Diagnosis of Giant Cell Tumor of Bone in Sweden Since 1958

BACKGROUND

The Swedish Cancer Registry (founded in 1958) constitutes a unique resource for epidemiological studies of giant cell tumor of bone with potential for use for population-based studies of incidence over time. The aim of this study was to provide what we believe is the first modern population-based assessment of the incidence trends of giant cell tumor, a unique osteoclastogenic lytic stromal tumor with both benign and malignant histological forms, and to compare the findings with data from the same registry on osteosarcoma, a tumor that may display similar histological characteristics.

METHODS

Cases were identified with use of codes for pathological bone tumor (International Classification of Diseases [ICD]-7 196). Specific morphological coding distinguishes benign (PAD 741) from malignant giant cell tumor (PAD 746) and osteosarcoma (PAD 766).

RESULTS

During the period of 1958 to 2011, 4625 bone tumors were reported, including 505 giant cell tumors (383 benign and 122 malignant) and 1152 osteosarcomas. From 1958 to 1982 the ratio of malignant to benign giant cell tumors was 1.3, whereas from 1983 to 2011 the ratio inverted to 0.09, suggesting a change in the reporting or diagnosis of malignant or benign cases. Cases of giant cell tumor diagnosed from 1983 to 2011 displayed an age and sex distribution (median age at diagnosis, 34.0 years; 54% female) that were consistent with those in large published case series but differed from those in 1958 to 1982 (median age at diagnosis, 31.5 years; 48% female). The most current data (1983 to 2011) showed the giant cell tumor incidence in Sweden to be 1.3 per million per year, while the osteosarcoma incidence was 2.3 per million per year.

CONCLUSIONS

Early Swedish Cancer Registry data (1958 to 1982) revealed a higher proportion of malignant giant cell tumors than seen in large sequential case series and a distinct age and sex profile compared with more recent data (1983 to 2011). This likely represents changes in the diagnostic workup and introduction of multidisciplinary review of giant-cell-containing tumors around 1982. Recent data may reflect the impact of expert centralized biopsy and multidisciplinary case review and more comprehensive reporting of benign giant cell tumors.

Regional variation and challenges in estimating the incidence of giant cell tumor of bone

BACKGROUND

Estimating the incidence of giant cell tumor of bone is challenging because few population-based cancer registries record benign bone tumors. We compared two approaches, the indirect (relative index) estimation approach used in The Burden of Musculoskeletal Diseases in the United States (BMUS) and a direct incidence rate approach (from registries that record giant cell tumor), to estimate giant cell tumor incidence in France, Germany, Italy, Spain, the U.K., Sweden, Australia, Canada, Japan, and the U.S.

METHODS

Giant cell tumor of bone incidence was calculated with use of the BMUS relative index of giant cell tumor to osteosarcoma in three scenarios (low, base case, and high) from case series. We compared the BMUS approach with the latest data from tumor registries in Australia (1972 to 1996), Japan (2006 to 2008), and Sweden (1993 to 2011) that record giant cell tumors. United Nations population estimates were used to project results to 2013.

RESULTS

The low scenario in the BMUS approach reflects data from Unni and Inwards; the incidence of giant cell tumor of bone is 0.34 relative to osteosarcoma. As the incidence of osteosarcoma is 31.4% of the total incidence of bone and joint cancers, the incidence of giant cell tumor is 0.11 times that of all bone and joint cancers. The base scenario reflects the series by Mirra et al., with a giant cell tumor incidence of 0.47 relative to osteosarcoma (0.15 to all bone and joint cancers). The high scenario reflects the series by Ward, with an incidence of 0.84 relative to osteosarcoma (0.26 to all bone and joint cancers). Differences among the three series reflect referral to a national center of excellence compared with referral to a local oncology practice. Registry data indicated a giant cell tumor incidence rate per million per year of 1.33 in Australia, 1.03 in Japan, and 1.11 in Sweden in 2013. The estimated incidence rate per million in the ten countries in 2013 ranged from 1.03 (Japan) to 1.17 (Canada) with use of the registry-based approach and from 0.73 (Japan) for the low scenario) to 2.20 (Germany) for the base case with use of the BMUS approach.

CONCLUSIONS

Giant cell tumor of bone affects approximately one person per million per year in the ten countries studied. Estimates derived with use of age-specific incidences from tumor registries were typically within the range of the low and base case BMUS scenarios. We recommend the registry-derived method for estimating the incidence of giant cell tumor.