Discovered on gastrointestinal stromal tumour 1 (DOG1): a useful immunohistochemical marker for diagnosing chondroblastoma.

AIMS: Cellular areas of chondroblastoma are composed of polygonal chondroblasts with indented nuclei and scattered osteoclast-type multinucleated cells. To learn more about the phenotype of chondroblasts, we investigated the expression of several established immunohistochemical markers in chondroblastomas. METHODS AND RESULTS: Nine chondroblastomas were analysed using immunohistochemical antibodies [CD34, α-smooth muscle actin (α-SMA), DOG1, CD117, AE1/AE3 and CD163]. Ten chondromyxoid fibromas, seven giant cell tumours of bone and four foetal proximal femurs were also analysed. The cellular areas of each chondroblastoma contained nests of DOG1(+) αSMA(+) CD117(-) CD34(-) chondroblasts, a phenotype that was not detected in chondromyxoid fibroma cases or in giant cell tumours. Although AE1/AE3 was expressed in all chondroblastomas, the staining intensity and proportion of the positive cells varied widely. Intra-lesional CD163(+) macrophages were detected in all cases of chondroblastoma, chondromyxoid fibroma and giant cell tumours. CONCLUSIONS: Our results demonstrated nests of membranous DOG1(+) chondroblasts located within cellular portions of chondroblastoma containing diffuse heterogeneous infiltrates of mostly DOG1(-) chondroblasts, CD163(+) macrophages and multinucleated osteoclastic giant cells. Thus, chondroblastoma can be added to the tumours that are usually positive for DOG1, alongside gastrointestinal stromal tumour (GIST), rare solid-pseudopapillary neoplasms of the pancreas and exceptional mesenchymal tumours including uterine type retroperitoneal leiomyoma, peritoneal leiomyomatosis and synovial sarcoma.

Phenotypic diversity in chondromyxoid fibroma reveals differentiation pattern of tumor mimicking fetal cartilage canals development: an immunohistochemical study.

Chondromyxoid fibroma represents a rare benign cartilaginous tumor of young patients occurring in a subcortical metaphyseal location. The histogenesis of chondromyxoid fibroma has not yet been postulated, even though the conventional histology and recent immunohistochemical studies on phenotype of the mesenchymal cells and extracellular matrix components suggested its origin in immature cartilage. Therefore, we wished to compare the morphological pattern of immature cartilage tissue with chondromyxoid fibroma to investigate a possible developmental counterpart of chondromyxoid fibroma. Archival paraffin-embedded tissues from 4 fetal femora and 10 cases of chondromyxoid fibroma were analyzed simultaneously using histochemistry (safranin O) and established immunohistochemical antibodies (CD34, CD163, and smooth muscle actin). Vascularized cartilage canals growing into the fetal cartilage from the perichondrium displayed characteristic glomeruloid structures with central arterioles within the immature mesenchymal stroma and numerous superficial sinusoidal blood vessels accompanied by macrophage infiltration. Similarly, each case of chondromyxoid fibroma demonstrated admixture of two characteristic components: immature fibrous tissue of vascularized stroma with accumulation of macrophages in areas of superficial sinusoidal proliferation, and variable amounts of lobulated chondroid tissue. Based on the observed substantial morphological similarity between the cartilage canals and chondromyxoid fibroma, we suggest that the chondromyxoid fibroma represents a neoplasm originating from or mimicking the fetal cartilage canals within the immature cartilage.