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Chondromyxoid Fibroma


- Discussion:
    - locally painfull benign cartilaginous lesion of bone;
    - it occurrs in adolescents;
    - located in metaphyses of major long bones;
    - this lesion most often presents as an active stage 2 lesion which is locally destructive & has a high recurrance rate (up to 25%);
    - it does not undergo malignant transformation;


- Diagnostic Studies:
    - radiographs reveal an eccentric radiolucent defect w/ no calcification;
         - adjacent cortex may be expanded thinned or even absent;
         - look for sclerotic and scalloped rim;
    - typically located in the metaphyseal region of long bones, and in some cases it is possible for it to invade the epiphyseal plate;
    - radiographic differential diagnosis:
         - nonossifying fibroma and ABC;


- Histology:
    - lobulated areas of spindle shaped cells and abundant myxoid or chondroid intercellular material;
    - low magnification reveals lobulations;
    - transition from hyaline cartilage to more cellular regions may be abrupt;
    - shows immature myxoid cartilage w/ stellate shaped chondrocytes enmeshed in lightly staining myxomatous chondroid matrix;
    - distributed throughout lesion are strands of benign fibrous tissue and small multinucleated giant cells;
           - benign giant cells are usually seen between the lobules of tumor;
    - pleomorphic cellular pattern is typical;
    - diff dx:
           - chondrosarcoma:
                  - in CMF pesence of large pleomorphic cells w/ hyperchromatic nuclei may result in false dx of chondrosarcoma;
           - chondroblastoma:
                  - CMF may be indistinguishable from chondroblastoma, however, CMF is metaphyseal tumor whereas chondroblastoma is epiphyseal;


- Treatment:
    - curettage is indicated for well encapsulated stage 2 lesions;
    - stage 3 lesions, most often seen in the pelvis, require wide excision to prevent recurrance