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Histology of Chondroblastoma

- Discussion:
    - shows characteristic "cobblestone" pattern;
    - areas of round, plump chondroblasts (stones), enmeshed in chondroid matrix;
    - nodular areas of a chondroid tissue are prominent;
    - cartilagenous matrix may have small foci of calcification between between chondroblasts (chicken wire calcification) around islands of cartilage;
            - calcification helps to separate chondroblastoma from giant cell tumor;
    - cytoplasm: may be pale, and may have an octagonal shape due to abutman against other tumor cells;
    - nuclei: are homogenous & oval & contain groove,  which resembles EOG;
    - secondary Aneurysmal bone cyst
            - about 17% of chondroblastomas show features c/w ABC;
            - may result in grossly hemorrhagic or cystic specimen;
    - clumps of giant cells are found adjacent to areas of spindle cell stroma;
    - demonstrates positive S-100 reactivity;


- Diff Dx:
    - tuberculosis:
           - can cause lytic defects in epiphyseal bone;
    - rheumatoid synovitis
    - pigmented villonodular synovitis:
    - chondrosarcoma:
           - may confused w/ chondrosarcoma due to pleomorphic cellular pattern, mitotic figures & multinucleated giant cells between chondroid areas