New insights into the phenotype of human dendritic cell populations.

HLDA10 is the Tenth Human Leukocyte Differentiation Antigen (HLDA) Workshop. The HLDA Workshops provide a mechanism to allocate cluster of differentiation (CD) nomenclature by engaging in interlaboratory studies. As the host laboratory, we invited researchers from national and international academic and commercial institutions to submit monoclonal antibodies (mAbs) to human leukocyte surface membrane molecules, particularly those that recognised molecules on human myeloid cell populations and dendritic cells (DCs). These mAbs were tested for activity and then distributed as a blinded panel to 15 international laboratories to test on different leukocyte populations. These populations included blood DCs, skin-derived DCs, tonsil leukocytes, monocyte-derived DCs, CD34-derived DCs, macrophage populations and diagnostic acute myeloid leukaemia and lymphoma samples. Each laboratory was provided with enough mAb to perform five repeat experiments. Here, we summarise the reactivity of different mAb to 68 different cell-surface molecules expressed by human myeloid and DC populations. Submitted mAbs to some of the molecules were further validated to collate data required to designate a formal CD number. This collaborative process provides the broader scientific community with an invaluable data set validating mAbs to leukocyte-surface molecules.

Primary Ewing's sarcoma family of tumors arising from the broad ligament.

We report a case of a primary Ewing's sarcoma family of tumors (ESFT) that was an incidental finding in the broad ligament of a 53-year-old woman. ESFT now includes tumors previously described as Askin tumor, neuroepithelioma, extraskeletal Ewing's sarcoma, and peripheral primitive neuroectodermal tumor. This is because of the discovery that all of the above tumors contain a specific gene rearrangement involving chromosome 22q12. On microscopic examination, the tumor was composed of small, round cells with mild nuclear pleomorphism and scant eosinophilic cytoplasm. There were large areas of tumor necrosis and numerous mitoses. Immunohistochemically, there was strong membrane staining for CD99 and weak focal staining for CD56 and neuron specific enolase. Fluorescence in situ hybridization revealed a separation of the breakapart probe on chromosome 22q12 consistent with the presence of a gene rearrangement, supporting the diagnosis of ESFT. We believe the importance of recognizing the existence of a primary ESFT in the broad ligament as some primary tumors of the gynecological tract and of other systems may resemble it histologically. To the best of our knowledge, our case is the second case of extraskeletal Ewings sarcoma arising from the broad ligament but the first case that is confirmed by strong CD99 positivity and supported by fluorescence in situ hybridization.