CT-guided FNAB of intra-abdominal desmoplastic small round cell tumor (DSRCT): A case report with presentation of cytologic and immunocytochemical features Maria Kalfa1, Eirini Klapsinou1, Theodoros Filippidis2, Sophia Markidou1 1Department of Cytopathology, Diagnostic & Therapeutic Center of Athens Hygeia, Athens, Greece 2Micromedica Histopathology Center, Athens, Greece INTRODUCTION Intra-abdominal DSRCT is an aggressive malignancy primarily affecting children and young males described as a distinct clinicopathologic entity in 1989 by Gerald and Rosai. CASE REPORT We report a case of a 22-year old man with multiple peritoneal masses, a large quantity of ascitic fluid, nodules in the liver and spleen surface involvement. CT-guided FNAB was performed on peritoneal masses. 2500 ml ascitic fluid were also aspirated. Air-dried and alcohol-fixed smears for Giemsa and Papanicolaou stains and cellblocks were prepared from both materials available for immunocytochemistry and cytogenetics. In both specimens microscopy showed small, malignant cells singly or in clusters with round to oval nuclei with finely granular chromatin, scanty cytoplasm and nuclear molding. Scanty desmoplastic stroma was observed. A diagnosis of small round cell tumor (SRCT) was initially suggested. Immunocytochemistry showed positivity of tumor cells for pankeratin, focal staining for desmin with dotlike paranuclear localization, focal cytoplasmic stain for WT1 and CD56 and negativity for vimentin,myogenin, NSE, LCA, S-100,chromogranin, TTF-1, synaptophysin, CK5/6 and CD57. Because of simultaneous expression of epithelial, muscular and in a lesser degree neural markers in tumor cells and in conjunction with the typical clinical presentation, a diagnosis of intra-abdominal DSRCT was made. Histology of abdominal masses showed solid nests of small cells, surrounded by dense stroma, with similar immunohistochemical findings and confirmed the cytologic diagnosis. Air-dried smear, MGG stain Alcohol-fixed smear, Papanicolaou stain Cell block section, H&E stain Cell block section, WT-1 stain Cell block section, CD56 stain Cell block section, Pankeratin stain Cell block section, Desmin stain Cell block section, CAM-5.2 stain DSRCT can be diagnosed with cytology in combination with immunocytochemistry and should be included in the differential diagnosis of SRCTs arising in intra-abdominal sites in children and young adults. CONCLUSION