A Retroperitoneal/omental tumor with characteristics of Ewing’s sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and desmoplastic small round cell tumor (DSRCT) with unique pathologic and immunohistochemical features, presented as a renal tumor

摘要

We present a unique case of retroperitoneal/omental tumor with characteristics of Ewing’s sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and desmoplastic small round cell tumor (DSRCT) in a young adult. This highly aggressive neoplasm must be distinguished from other primitive tumors that require different therapy. The tumor presented as a large mass originating from the right kidney, an evolving as a perirenal mass invading the kidney. Multiple recurrences within the following four post-operative years demonstrated a tumor with a unique location and the coexpression of FL-1 and WT1. Immunohistochemistry of the tumor shows the known immunophenotypic overlap between EWS/pPNET and DSRCT. The capacity of simultaneous multidirectional phenotypical expression of the tumor may serve a support to the concept that EWS/pPNET and DSRCT form single group tumors. The patient died of disease four years post-operatively. The accurate distinction between these entities has clear prognostic and therapeutic implications. Introduction Ewing’s sarcoma/peripheral primitive neuroectodermal tumor constitutes a group of malignant small round cell tumors (SRCTs) of presumed neuroectodermal origin that occur most commonly in bone and soft tissues of children and young adults[1]. Accurate diagnosis of SRCTs is hindered by their significant morphologic and genetic overlap and complicated by their rarity. EWS/PNET is characterized by a balanced chromosomal translocation which generates a fusion transcript of the EWS gene and the Friend leukemia virus integration 1 (FLI-1). Cases of primary EWS/pPNET of the kidney[2], retroperitoneum[3], and omentum[4]have been sporadically reported in the literature. To our knowledge, the present case is the second case to be reported of EWS/pPNET observed in retroperitoneum/omentum as a multilocular cyst with intracystic hemorrhage and necrosis. The tumor was unique with its location, and the coexpression of FLI-1 and Wilms tumor–associated (WT1) tumor suppressor gene, which are diagnostic of EWS/pPNET[5] and DSRCT[6], respectively. Case report A 28 years-old man presented with a recent vague right lomber pain had a right nephrectomy in a community hospital of a small city with a final diagnosis of high grade, sarcomatoid renal cell carcinoma, with disseminated perirenal infiltration. Two years later, he was referred to admit to the urology department for further evaluation. The laboratory studies was within normal limits. MRI and CT scan demonstrated multiple mass located on the left lower quadrant of the abdomen; one was on the anterolateral aspect of the descending colon extending into the inferior aspect of the liver; the second mass was located retrocecally and anterior to the right iliac muscle, lateral to the the right psoas muscl, and the third one was anterior to iliac artery bifurcation, and next to the right psoas muscle. They showed internal cystic degenerations, were lobulated, necrotic and highly hemorrhagic. Excision of the tumor was followed by four cycles of polychemotherapy (gemcitabine and cysplatin) which was switched to phosphamide and doxorubicine following a follow-up CT scan. Six months later CT scan was demonstrated disease progression. Abdominal ultrasonography (USG) and the CT scan was demonstrated a huge cystic mass with lobulated contours, measuring 24 cm in cranio-caudal dimension. There was a large, hemorrhagic and cystic tumor inferior to the liver, involving omental tissue and the right psoas muscle. Six months later he was readmitted and the omental mass was excised, a left double–j catheter was inserted. Three months later, subhepatic and mesenteric masses disappeared but the right pelvic hipodense residual lesion expanded. The double-j catheter was removed and two cycles of chemotherapy (vincristine, endoxan) was administered. Four months later he was readmitted, and referred to the radiation oncology for radiotherapy. Abdominal USG and CT scan was revealed some benefi