This report presents a dedifferentiated chondrosarcoma with a unique pathologic feature. A 63-year-old man was referred with pain and a soft tissue mass in the left groin. A plain radiograph showed a mineralization in the proximal femur with partially osteolytic foci and an abnormal shadow in the soft tissue. Magnetic resonance imaging scans showed an inhomogeneous lesion with intermediate to partially low signal intensity on T1-weighted image and intermediate to high signal intensity on T2-weighted image. Microscopically, the tumor in the femur is a low-grade chondrosarcoma and the component of soft tissue was a high-grade sarcomatous lesion with an epithelial arrangement of tumor cells. A diffuse immunoreactivity to both vimentin and c-kit (CD117) antibodies was detected in the high-grade component. A dedifferentiated component is similar to those of gastrointestinal stromal tumor (GIST). This is the first case of dedifferentiated chondrosarcoma with a high-grade component mimicking a GIST.
Dahlin and Beabout first defined dedifferentiated chondrosarcoma in 1971 as a variant of chondrosarcoma that consisted of a benign or low-grade malignant cartilagenous component with a high-grade noncatilagious sarcomatous component [
A 63-year-old man was referred with a soft tissue mass in the left groin accompanying with severe pain for 3 months. The pain gradually increased and eventually disturbed walking. The patient had a history of intertrochanteric fracture in his left femur at 14 years of age, which was treated with casting for 2 months. The patient complained of discomfort and pain in the anterior chest one month before the presentation to the hospital and the diagnosis was angina pectoris. On physical examination, an elastic hard mass with a rough surface was palpated in the medial aspect of the left groin, measuring approximately 15 cm in the greatest diameter. The mass strongly adhered to the femur, but not to the skin. The patient felt tenderness in the mass. There was mild swelling around the soft tissue mass without local heat or redness. The range of motion in the left hip was slightly restricted. The laboratory tests showed marked increases of white blood cell count (10.700/mm3), c-reactive protein (7.6 mg/dl), erythrosedimentation rate (98 mm/h) at the presentation to the hospital. Alkaliphosphatase (307 U/ml) and serum calcium (10.0 mg/dl) concentrations also slightly increased. An anteroposterior plain radiograph showed a mineralization in the proximal femur with partially osteolytic foci and an abnormal shadow in the soft tissue medially adjacent to the femur (
The patient underwent an open biopsy for both bone and soft tissue components of the tumor. At biopsy, the soft tissue component showed a yellowish brown mass with a thin capsule-like tissue and the tumor in the femoral medulla consisted of ash-white friable tissue. Microscopically, the specimen from the femoral medulla consisted of cartilagious tissue, bone, and fibrous tissue (Figures 5(a) and (b)). Cartilagious tumor cells showed lowgrade nuclear atypia without multinucleated cells. Calcification was detected around the cartilaginous tissue. There was no osteoid in the specimen from the femoral medulla. The specimen from the femoral medulla was diagnosed as a low-grade chondrosarcoma (grade I) based on the criteria previously described [
cleaved collagen fibers, the amount of which varied form area to area (
Immunohistochemically, the tumor cells in the soft tissue component showed diffusely positive immunoreactivity for vimentin and c-kit (CD117) antibodies (Figures 7(a) and (b)). Weak immunoreactivity for bcl-2 protein and epithelial membrane antigen (EMA) antibodies was detected in low percentage of soft tissue component. The specimen from high-grade component did not show any immunoreactivity for desmin, alphasmooth muscle actin, S-100 protein, cytokeratin, CD34 antigen antibodies, HHF35, and HMB45.
The patient underwent an irradiation (45 Gy) for the tumor in the groin and a systemic chemotherapy (ifosfamide 8 g/body), but he died 3 months after presentation to the authors’ hospital.
Dedifferentiated chondrosarcoma was first described by Dahlin and Beabout in 1971 as a variant of chondrosarcoma that consisted of a benign or low-grade malignant cartilaginous component with a high-grade noncatilagious sarcomatous component [
osteosarcoma, rhabdomyosarcoma, leiomyosarcoma, nor giant cell tumor.
Gastrointestinal stromal tumor (GIST) was first introduced as a mesenchymal tumor in the gastrointestinal tract by Mazur and Clark [
Radiologic features in the current case are comparable with previous studies [10,20,21]. Previous study have demonstrated that 77% of radiographs and 86% of CT scans for dedifferentiated chondrosarcomas showed intraossous calcification and that endosteal scalloping was detected in 67% of radiographs and 90% of CT scans. In the current case, plain Radiographs and CT scans showed calcification in the medulla of femur and endosteal scalloping of cortex, suggesting cartilaginous tumor with invasive behavior. In the previous studies, MR imaging have shown unique imaging features of dedifferentiated chondrosarcomas [10,20,21]. MacSweeney et al. have proposed three MRI patterns in dedifferentiated chondrosarcomas: type1, two distinct signals with hyper- intense chondral lesion and reduced signal intensity of dedifferentiated component; type 2, mainly reduced signal intensity with partial signal void corresponding to matrix mineralization; type 3, a heteroginous signal intensity without evidence of underlying chondral component [
Dedifferentiated chondrosarcoma has a poor prognosis. The 5-year survival rate ranges form 10.5% - 29% [2-4,22-24]. Previous studies have shown prognostic factors for dedifferentiated chondrosarcoma. Michell et al. have proposed a benefit of chemotherapy for dedifferentiated chondrosarcoma [