Ertoy Baydar et al. Diagnostic Pathology (2020) 15:95 https://doi.org/10.1186/s13000-020-01015-w CASE REPORT Open Access Desmoplastic small round cell tumor of the kidney: a case report Dilek Ertoy Baydar1*† , Ayse Armutlu1†, Oguz Aydin2, Ayhan Dagdemir3 and Yarkin Kamil Yakupoglu4 Abstract Background: Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive neoplasm seen in children and young adults, usually manifested by involvement of abdominal serosa. Here, we present an unusual case of primary DSRCT of kidney. Case presentation: The patient was an 8-year-old girl with a large renal mass which was confused with primitive neuroectodermal tumor (PNET) in the needle biopsy. The tumor had a variegated histology revealing frequent pseudo-rosette formations, pseudopapillary architecture, rhabdoid, clear or pleomorphic cells in addition to typical small round cell morphology and desmoplasia. It showed immunohistochemical features of DSRCT, and EWSR1 re- arrangement. Conclusions: Proffering this diagnosis is particularly difficult for tumors of viscera because of the incognizance of the entity in these locations. Moreover, DSRCT is a great mimicker and may get easily confused with more common kidney malignancies of childhood such as Wilms tumor, PNET/EWS, rhabdoid tumor, clear cell sarcoma, and other small round cell tumors as well as renal cell carcinomas. The distinction is critical as the accurate therapeutic approach will require correct diagnosis. Keywords: Desmoplastic small round cell tumor, Kidney, WT1, EWSR1, Case report Background are extremely rare with only a few cases reported in Desmoplastic small round cell tumor (DSRCT) is a rare, lungs, ovary, soft tissues, bones, intracranial and sinona- distinct entity that was first described by Gerald and sal locations [2, 3]. Rosai in 1989 [1]. Predilection for adolescent males, DSRCT primary of the kidney was first described by predominant intraabdominal location involving serosal Su, et al. [4] in 2004 and since then only a total of surfaces, nesting pattern of growth, focal rhabdoid 12 cases have been reported in the literature (Table 1) morphology, prominent desmoplastic reaction, immuno- [5–12]. Herein, we present the thirteenth case of histochemical reactivity for epithelial, neural and muscle renal DSRCT that had variant histological features markers, and highly aggressive clinical behavior are its mimicking various types of other neoplasia. The main features. DSRCT shows a specific reciprocal pathologic diagnosis of this entity can be markedly chromosomal translocation, t(11;22)(p13;q12) (EWSR1- challenging when it develops in visceral organs such WT1 fusion) which generates a chimerical protein with as kidney and especially if diverse and confounding transcriptional regulatory activity. Extraserosal DSRCTs microscopic features are present. * Correspondence: [email protected]; [email protected] Case presentation † Dilek Ertoy Baydar and Ayse Armutlu contributed equally to this work. Clinical history 1Department of Pathology, Koc University School of Medicine, Topkapi, 34010 Istanbul, Turkey An 8-year-old girl complained of abdominal pain and an Full list of author information is available at the end of the article ultrasonography found a large mass in her left kidney. © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. 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Table 1 Clinicopathologic features of the cases described in the literature (a) Ertoy Baydar Age Clinical R/L Gross Findings Microscopic Findings Immunohistochemistry Molecular Therapy Follow-up Publication / presentation side pathology Sex Case 41 / Incidental Left Renal mass at hilar region, Nests of small round blue cells CK (AE1/AE3) (+), Desmin (+), RT-PCR Surgery Alive (NED) at Su, et al., et al. Diagnostic Pathology 1 F 6x5x5 cm, invaded into within desmoplastic stroma; Vimentin (+), NSE (+), EMA (−), showing 18th mo. [4] perirenal soft tissue occasional rosette-like forma- CK7 and 20 (−), CD99 (−), S100 EWSR1-WT1 tions; necrosis and numerous (−), Chromogranin (−), fusion mitotic figures Synaptophysin (−) Case 7 / F Gross Left Confined within renal Small round undifferentiated Desmin (+), WT-1 (+), CD99 (+), RT-PCR Surgery + CT Alive (NED) at Eaton, 2 hematuria capsule, 3.7 × 3.7 × 3.2 cm cells, necrosis and epithelioid SMA (+), EMA (+), Myogenin (−) showing 12th mo. et al., [5] following a fall component EWSR1-WT1 fusion (2020)15:95 Case 6 / F Renal mass Left 3.7 cm mass confined to Nests, sheets or cords of small CK (+), Desmin (+), Vimentin (+), Dual color FISH Neoadjuvant Alive (NED) Egloff, 3b (no details kidney undifferentiated cells; WT1 (+), FLI-1 (+), CD56 (+); EMA showing CT + Surgery 24th mo. et al., [6] about clinical numerous mitotic figures, no (−), CD99 (−), Myogenin (−), S100 EWSR1-WT1 and Wang, presentations) desmoplasia (−), Chromogranin (−), Synapto- translocation et al., [7] physin (−) and RT-PCR showing Case 6 / F Left 13.4 cm mass showing CK (+), EMA (+), Desmin (+), EWSR1-WT1 Surgery + CT Pulmonary Wang, 4 renal sinus invasion Vimentin (+), CD99 (+), WT1 (+), fusion metastasis at et al., [7] FLI-1 (+), CD56 (+), Myogenin (−), 32nd mo. CT, S100 (−), Chromogranin (−), stem cell Synaptophysin (−) transplantation. NED a year later Case 6 / F Left 9 cm mass with perirenal CK (+), EMA (+), Desmin (+), Alive (NED) at 5 soft tissue and renal sinus Vimentin (+), CD99 (+), WT1 (+), 22nd mo invasion FLI-1 (+), CD56 (+), Myogenin (−), S100 (−), Chromogranin (−), Synaptophysin (−) Case 8/ Left 9.2 cm mass with renal EMA (+), Desmin (+), Vimentin (+), Intraabdomimal 6 M sinus invasion CD99 (+), WT1 (+), FLI-1 (+), CD56 recurrence and (+), CK (−), Myogenin (−), S100 liver metastasis (−), Chromogranin (−), Synapto- at 20th mo. physin (−) CT. AWD Case 14 / Gross Left 17.5x12x11 cm mass Small ovoid-spindle blue cells EMA (+), Desmin (+), Vimentin (+), RT-PCR Surgery + Liver and lung Collardeau- 7 F hematuria, invading renal sinus and in solid sheets and large nests; WT1 (+), CD56 (+), Chromogranin showing CT + local RT metastases at Frachon, fever and self- perinephric fat, and focally rare rosette-like structures; nu- (focal +), Synaptophysin (rare +), EWSR1-WT1 8th mo. et al., [8] disvovered ab- extending to Gerota’s merous mitotic figures; tumor CK (AE1/AE3) (−), CD99 (−), S100 fusion dominal mass fascia; metastatic lymph thrombi in perinephric blood (−) node in hilar region vessels Case 10 / Gross Right 14 × 11 cm mass Small blue round cells with CK (+), Desmin (+), CD99 (−), WT1 RT-PCR Surgery + Liver, lung, da Silva, 8 M hematuria, desmoplasia; occasional (+), FLI-1 (+); S100 (−), Chromo- showing CT + local RT bone, lymph et al., [9] abdominal rosette-like formations. granin (−), Synaptophysin (−) EWSR1-WT1 node pain, palpable fusion metastases. Page 2 of 9 mass AWD at 12th mo Table 1 Clinicopathologic features of the cases described in the literature (a) (Continued) Ertoy Baydar Age Clinical R/L Gross Findings Microscopic Findings Immunohistochemistry Molecular Therapy Follow-up Publication / presentation side pathology Sex Case 20 / Renal mass and Right 8 cm mass with areas of Elongated to round cells with CK (+), Desmin (+), Vimentin (+), FISH showing Surgery Pulmonary Rao, et al., et al. Diagnostic Pathology 9 M pulmonary hemorrhage and necrosis, scant cytoplasm in sheets and CD56 (+); WT1 (cytoplasmic +), EWSR11 metastases at [10] nodules invading renal vein grossly occasionally a vague nodular CD99 (−), MyoD1 (−), NSE (−), rearrangement presentation, (no details pattern, frequent mitotic RCC Ag (−), EMA (−), Myogenin and RT-PCR local recurrence about clinical activity, lacked prominent (−), S100 (−) showing after surgery. presentations) desmoplasia EWSR1-WT1 Exitus at 2nd fusion year Case 7/ Gross Left Polypoid mass confined to Spindled and polygonal tumor CD99 (+), Vimentin (+), Desmin FISH showing Surgery + Alive (NED) Eklund 10 M hematuria, the renal collecting system, cells, rare rosettes, low mitotic (focal+), Actin (focal+), WT1 EWSR1 CT + RT (duration et al., [11] microscopic extending into proximal rate (focal+), PAX2 (+); PAX8 (−) rearrangement, unknown) (2020)15:95 hematuria and and mid ureter, no karyotyping intermittent involvement of renal showing t(11; back pain 3 parenchyma 22) (p13;q12). years priorly Case 6/ Facial swelling Right 5.7 × 5.5 × 4.7 cm mass Sheets of poorly differentiated Bcl-2 (+), CD99 (+), desmin (+), RT-PCR No Metastatic Walton, 11 M and pain, with large areas of central round cells, no desmoplastic vimentin (+), CD56 (+), and FLI-1 showing information disease