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

Akpalo H, Lange C & Zustin J ?(2012) Histopathology similar to 60, 10991106 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, a-smooth muscle actin (a-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+aSMA+ 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.