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Year : 2008  |  Volume : 51  |  Issue : 4  |  Page : 561-562
Dedifferentiated chondrosarcoma of the femur mimicking a conventional giant cell tumor: A diagnostic pitfall

Department of Pathology, All India Institute of Medical Sciences, New Delhi, India

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How to cite this article:
Arora R, Sharma A, Dinda AK. Dedifferentiated chondrosarcoma of the femur mimicking a conventional giant cell tumor: A diagnostic pitfall. Indian J Pathol Microbiol 2008;51:561-2

How to cite this URL:
Arora R, Sharma A, Dinda AK. Dedifferentiated chondrosarcoma of the femur mimicking a conventional giant cell tumor: A diagnostic pitfall. Indian J Pathol Microbiol [serial online] 2008 [cited 2022 Jan 25];51:561-2. Available from: https://www.ijpmonline.org/text.asp?2008/51/4/561/43763


Dedifferentiation is referred to as the progression of a low-grade neoplasm into a higher grade lesion. Such a phenomenon in chondrosarcoma is characterized by the loss of cartilaginous phenotype. [1] In such cases, both the malignant cartilage and dedifferentiated non cartilaginous components coexist thus giving a biphasic appearance. While the cartilaginous component is usually a low-grade chondrosarcoma, the non cartilaginous component may show features of a high-grade sarcoma such as osteosarcoma, leiomyosarcoma, rhabdomyosarcoma, etc. However, considerable diagnostic difficulty may arise when the non cartilaginous component mimics a benign lesion.

A 35-year-old male presented with a history of swelling and discomfort in the right knee for the last 3 months. He was evaluated elsewhere for his complaints and a biopsy was performed that was interpreted as a giant cell tumor of bone. The patient was subsequently referred to our institute for further management. On examination, a fusiform firm lesion measuring about 8x8 cm was palpable on the medial aspect of the right knee. Review of the X-ray taken before the biopsy revealed a lytic expansile lesion in the medial femoral condyle. A magnetic resonance imaging (MRI) was performed that showed a fusiform lesion involving the right medial femoral condyle with extension to the adjacent muscle planes [Figure 1A]. The lesion exhibited focally confluent high signal intensity in T2W images and focal areas of low signal intensity in T1W images indicating the possibility of a biphasic lesion. With this variegated clinico-radiologic picture, the patient was taken for excision of the lesion and end prosthesis placement.

On gross examination, a lesion measuring 8x7x6 cm was seen near the medial condyle. On serial sectioning, an unencapsulated grayish-white lesion was identified in the metaphyseal region of the right femur, extending up to the overlying articular surface and surrounding muscle plane [Figure 1B]. A histological examination of the excised specimen showed a biphasic tumor comprising of chondroid and non chondroid areas showing an abrupt transition [Figure 2]. The chondroid areas showed a moderate increase in cellularity with frequent binucleation, a moderate degree of nuclear enlargement and pleomorphism [Figure 3]. Scattered foci of calcification and endochondral ossification were also seen. The cartilaginous areas showed focal S-100 positivity. The stroma was composed of numerous unevenly distributed osteoclastic-like giant cells associated with stromal mononuclear cells. These areas were microscopically indistinguishable from a conventional giant cell tumor [Figure 4]. At other places, spindle cells with irregular nuclear contours but lacking obvious nuclear pleomorphism were seen. These areas were cellular and showed a mitotic count of 4-5 per 10 high power fields. The MIB-1 labeling index in these areas was about 20%. The non cartilaginous component was seen extending into the surrounding soft tissue. However, none of the areas showed obvious features of a high grade sarcoma. Based on these histological findings, a diagnosis of dedifferentiated chondrosarcoma with the non cartilaginous component mimicking giant cell tumor of bone was rendered. The patient is currently on follow-up for 10 months with no evidence of recurrence or metastases.

Prognosis of dedifferentiated chondrosar- coma is considered poor in contrast to conventional chondrosarcoma with a five-year survival rate of only 10.5%. However, in the small number of cases described, including the present case, it has been observed that the presence of a giant, cell-rich, non cartilaginous component may indicate a better prognosis. [2],[3],[4],[5]

Thus, it is important to be aware of this variant of dedifferentiated chondrosarcoma to avoid the misdiagnosis of conventional giant cell tumor of the bone considering that the prognosis and survival in these two entities are very different. In addition, the evaluation of limited biopsies in such lesions can cause serious diagnostic error if only the giant cell containing area is sampled and hence should be avoided.

   References Top

1.Dahlin DC, Beabout JW. Dedifferentiation of low grade chondrosarcomas. Cancer 1971;28:461-6.  Back to cited text no. 1  [PUBMED]  
2.Mirra JM. Bone tumours. Clinical, radiologic and pathologic correlations. 1 st ed. Philadelphia: Lea and Febinger; 1989. p. 565-9.  Back to cited text no. 2    
3.Sissons HA, Malten JA, Lewis MM. Dedifferentiated chondrosarcoma: Report of an unusual case. J Bone Joint Surg 1991;73:294-300.  Back to cited text no. 3    
4.Ishida T, Dorfman HD, Habermann ET. Dedifferentiated chondrosarcoma of humerus with giant cell tumour like features. Skeletal Radiol 1995;24:76-80.  Back to cited text no. 4  [PUBMED]  
5.Estrada EG, Ayala AG, Lewis V, Czerniak B. Dedifferentiated chondrosarcoma with a noncartilagenous component mimicking a conventional giant cell tumour of bone. Ann Diagn Pathol 2002;6:159-63.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]

Correspondence Address:
Alok Sharma
Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.43763

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  [Figure 1A], [Figure 1B], [Figure 2], [Figure 3], [Figure 4]

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