Image Description
Differential Diagnosis: Mesenchymal chondrosarcoma (MC) must be differentiated from other malignant small cell tumors of bone and soft tissue. The histologic hallmark of MC is a biphasic appearance consisting of undifferentiated small round to spindled cells admixed with islands of mature cartilage. The combination of these two components is virtually diagnostic of MC.
The biphasic nature of the tumor may not be obvious in limited biopsy specimens that often contain only 1 of the 2 components. If the sample contains predominance of well-differentiated hyaline cartilage, it can be mistaken for conventional chondrosarcoma. Radiographic features of MC also resemble those of conventional chondrosarcoma.
If chondroid foci are inconspicuous and the specimen consists mostly of sheets of small undifferentiated mesenchymal cells (as seen in this image), then the differential diagnosis includes other malignant small round blue cell tumors such as Ewing sarcoma/PNET, rhabdomyosarcoma, poorly-differentiated synovial sarcoma, small cell osteosarcoma, and even malignant lymphoma.
discussion continues in the next image......
The biphasic nature of the tumor may not be obvious in limited biopsy specimens that often contain only 1 of the 2 components. If the sample contains predominance of well-differentiated hyaline cartilage, it can be mistaken for conventional chondrosarcoma. Radiographic features of MC also resemble those of conventional chondrosarcoma.
If chondroid foci are inconspicuous and the specimen consists mostly of sheets of small undifferentiated mesenchymal cells (as seen in this image), then the differential diagnosis includes other malignant small round blue cell tumors such as Ewing sarcoma/PNET, rhabdomyosarcoma, poorly-differentiated synovial sarcoma, small cell osteosarcoma, and even malignant lymphoma.
discussion continues in the next image......