Primary Undifferentiated Sarcoma of the Kidney ...

LETTER

Primary Undifferentiated Sarcoma of the Kidney Harboring a Novel Variant of CIC-DUX4 Gene Fusion To the Editor: In recent issues of this journal, Yoshida et al1 reported on CIC-rearranged sarcomas, and Falzarano et al2 described renal cell carcinomas (RCCs) in patients previously treated

TO THE

EDITOR

for neuroblastoma (NB). Herein, we describe a primary renal CIC-DUX4 sarcoma, originally diagnosed as Wilms tumor (WT), in a patient previously treated for contralateral stage 4 NB. CIC-DUX4 sarcoma was retrospectively suspected after WT1 nuclear staining was reported in 95% and 70% of CIC-rearranged sarcomas.1,3 CIC-DUX4 undifferentiated sarcomas are a group of EWSR1negative primitive tumors or Ewinglike sarcomas with fusion of the human homologue of the Drosophila capicua (CIC) gene on chromosome

19 and the double-homeobox 4 (DUX4) retrogene on chromosome 4 or 10.1,3 Occasional peripheral tumors harbor variant translocation in which the CIC gene is fused with the forkhead box O4 (FOXO4) gene on the X chromosome.4 Yoshida et al1 reported that the majority of their CIC-rearranged sarcomas demonstrated nuclear immunoreactivity for WT1 protein, are positive for calretinin, and negative for NKX2.2. The vast majority of these sarcomas occur primarily in peripheral soft tissues,1,3 but visceral cases including the brain are reported.1,5,6

FIGURE 1. A, The gross appearance of the cut surface of the nephrectomy specimen shows a myxoid tumor with a lobulated and infiltrative periphery, extensive hemorrhage, and necrosis. B, The hematoxylin and eosin section shows a spindle cell component with fascicular arrangement. C, The high power of the spindle cells demonstrates coarse nuclear chromatin. D, A focus with a prominent hemangiopericytoma-like vascular pattern is depicted. E, In this focus, microcyst formations with the hobnail-like appearance of a subset of cells lining the cyst are present. F, In the round cell component focal myxoid stroma (top) is noted, and on high power there is overlap of cells with vesicular nuclei and prominent nucleoli (bottom). Am J Surg Pathol

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FIGURE 2. A, IHC stains demonstrate diffuse positive nuclear (left) and focal cytoplasmic staining (right) with the antibody to the N-terminal of WT1. B, Left: FISH demonstrates rearrangement of the centromeric probe (red) and telomeric probe (green) of the CIC gene. Right: Note separation of the probes in the foreground (arrows), whereas there is overlap of the probes in the background consistent with lack of CIC rearrangement (between arrows).

We encountered a right kidney tumor from a 9-year-old boy, before CIC-DUX4 sarcomas being well characterized, previously treated with chemotherapy, radiation, and stem cell transplantation for his left NB diagnosed at 4 years of age. The

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radical nephrectomy demonstrated a 10 cm tumor that invaded perirenal fat and the hilum. The cut surface had a lobulated periphery, myxoid appearance, and approximately 50% necrosis (Fig. 1A). On hematoxylin and eosin sections, a spindle cell comCopyright

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ponent composed of cells with coarse nuclear chromatin (Figs. 1B, C) was noted, but a round cell component predominated. Foci of hemangiopericytoma-like vascular growth pattern and microcysts partially lined by hobnail-like cells were present (Figs. 1D, E).

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The predominant round cells were focally set in a myxoid stroma and had vesicular nuclei with prominent nucleoli (Fig. 1F). The mitotic rate was >20 mitoses per 10 high-power fields. Hilar lymph nodes were negative for metastases from his renal primary, but one hilar lymph node demonstrated abundant neuropil and ganglion cells, consistent with his previously treated contralateral NB (Supplemental Figure, Supplemental Digital Content 1, http:// links.lww.com/PAS/A387). Immunohistochemical (IHC) stains demonstrated membranous CD99 positivity in approximately 50% of neoplastic cells, diffuse positivity for bcl2, and focal cytokeratin positivity. Desmin, chromogranin, and S-100 were negative. Fluorescence in situ hybridization (FISH) analyses for SYT (SS18) and EWSR1 gene rearrangements were negative. Subsequently, diffuse nuclear positive IHC staining with WT1 (Nterminal) (Fig. 2A) and INI were demonstrated resulting in a diagnosis of undifferentiated stromal WT in concert with expert external review. The patient underwent chemotherapy and local radiation for favorable histology WT. However, he ultimately succumbed to lung and brain metastases 18 months after the initial diagnosis of WT. Recently, CIC gene rearrangement was identified in 193/200 (96.5%) of the tumor nuclei by FISH (Fig. 2B), and comprehensive genomic profiling identified a novel variant of a CIC-DUX4 fusion involving exon 18 of the CIC gene and exon 1 of the DUX4 gene (Molecular Methodology and Figure, Supplemental Digital Content 2, http://links. lww.com/PAS/A388). Subsequently, focal positive immunoreactivity with calretinin and negative staining with NKX2.2 were demonstrated. Retrospectively, many histologic features of this case are identical to that described subsequently in CIC-rearranged sarcomas.1,3 Yoshida et al1 alluded to a focal hemangiopericytoma-like vasculature in one of their cases, but this finding is not well recognized in these tumors. A diagnosis of WT is straightforward in the vast majority of cases when tubular epithelium and/or blastemal compoCopyright

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nents are present and easily rendered on H&E sections. Although the majority of WTs are sporadic and occur under the age of 5 years, the above forms of WT tend to occur in older children and are associated with perilobar nephrogenic rests that help in the diagnosis when present. Nodular and serpentine blastemal patterns of WT are usually easily recognized, but the diffuse form may be more challenging. However, the closely packed round or oval overlapping nuclei of blastemal cells have evenly distributed slightly coarse chromatin and small nucleoli in contrast to the round vesicular nuclei and prominent nucleoli or elongated spindle cells of CIC-rearranged sarcoma.1,3,7 Stromal predominant WT tends to occur in younger children, is associated with intralobar nephrogenic rests and usually accompanied by minor epithelial and blastemal components.7 Pure undifferentiated stromal WT requires IHC staining with WT1 for rendering an appropriate diagnosis as reported by Shao et al.8 Of note, Ellison and colleagues also reported WT1 staining in primary Ewing sarcoma/ primitive neuroectodermal tumor of the kidney. However, a subset of these cases lacked confirmation of the Ewing sarcoma/primitive neuroectodermal tumor diagnosis by reverse transcription polymerase chain reaction or FISH leading the authors to suggest that those EWSR1-negative cases might represent undifferentiated WTs.9 Therefore, when undifferentiated stromal WT and sarcoma are in the differential diagnosis, molecular testing including CIC rearrangement is indicated. Interestingly, Tagarelli et al10 described 2 cases of primary renal undifferentiated sarcoma in a report of 12 primary sarcomas of the kidney, but detailed morphologic descriptions, immunophenotypes, or molecular profiles were not reported. Clearly it would be of interest to assess the above undifferentiated tumors for CIC rearrangement. Previous studies have shown breakpoints in exons 19, 16, and 20 of the CIC gene.4,6,11 The novel breakpoint in exon 18 of CIC identified by CPG in this case supports the notion that the structure of the CIC gene fa-



cilitates multiple rearrangements and further justifies CIC FISH testing with break-apart probes for clinical practice. This primary renal CIC-DUX4 sarcoma developed 5 years after treatment for stage 4 NB. As reported by Falzarano and colleagues and in the current World Health Organization classification, a subset of RCCs occur in patients previously treated for NB.2,12 These findings suggest that NB therapy might be involved in the pathogenesis of this CIC-DUX4 sarcoma and NB-related RCCs. In conclusion, this primary renal CIC-DUX4 sarcoma expands the list of renal mesenchymal tumors with underlying genomic alterations13,14 and underscores the potential pitfall of WT1 staining in undifferentiated renal tumors. As sarcoma therapy is more intensive than WT therapy, distinguishing sarcoma, including CIC-rearranged sarcoma, from WT has significant therapeutic implications. Finally, it is left to be seen whether further sarcomas will be reported in survivors of NB.

Shamlal Mangray, MB, BS* Gino R. Somers, MB, BS, PhD, FRCPAw Jie He, PhDz Shan Zhong, PhDz Mary Shago, PhDw Diana O. Treaba, MD* Kara A. Lombardo, BS* Siraj M. Ali, MD, PhDz Evgeny Yakirevich, MD, DSc* *Department of Pathology, Rhode Island Hospital & Alpert Medical School of Brown University, Providence, RI wDepartment of Pathology, The Hospital for Sick Children & University of Toronto, Toronto, ON, Canada zFoundation Medicine Inc. Cambridge, MA

Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Website, www.ajsp.com. Conflicts of Interest and Source of Funding: J.H., S.Z., and S.M.A. are employees of and have equity interests in Foundation Medicine Inc. For the remaining authors none were declared. www.ajsp.com |

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ACKNOWLEDGMENTS We are very grateful to Ronald DeLellis who reviewed this manuscript and offered many insightful suggestions. REFERENCES 1. Yoshida A, Goto K, Kodaira M, et al. CIC-rearranged sarcomas. A study of 20 cases and comparisons with Ewing sarcomas. Am J Surg Pathol. 2016;40:313–323. 2. Falzarano SM, McKenney JK, Montironi R, et al. Renal cell carcinoma occurring in patients with prior neuroblastoma. A heterogenous group of neoplasms. Am J Surg Pathol. 2016;40:989–997. 3. Specht K, Sung Y-S, Zhang L, et al. Distinct transcriptional signature and immunoprofile of CIC-DUX4 positive round cell tumors compared to EWSR1-rearranged Ewing sarcomas- further evidence towards distinct pathologic entities. Genes Chromosomes Cancer. 2014;53:622–633. 4. Sugita S, Arai Y, Tonooka A, et al. A novel CIC-FOXO4 gene fusion in undifferentiated small round cell sarcoma. A genetically distinct variant of Ewing-like sarcoma. Am J Surg Pathol. 2014;38:1571–1576.

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5. Bielle F, Zanello M, Guillemot D, et al. Unusual primary cerebral localization of a CIC-DUX4 translocation tumor of the Ewing sarcoma family. Acta Neuropathol. 2014;128:309–311. 6. Sturm D, Orr BA, Toprak UH, et al. New brain entities emerge from molecular classification of CNS-PNETs. Cell. 2016;164: 1060–1072. 7. Argani P, Bruder E, Dehner L, et al. Nephroblastic and cystic tumors occurring mainly in children. In: Moch H, Humphrey PA, Ulbright TM, Reuter VE, eds. WHO Classification of Tumors of the Urinary System and Male Genital Organs. Lyon: International Agency for Research on Cancer; 2016:48–53. 8. Shao L, Hill DA, Perlman EJ. Expression of WT-1, Bcl-2, and CD34 by primary renal spindle cell tumors in children. Pediatr Dev Pathol. 2004;7:577–582. 9. Ellison DA, Parham DM, Bridge J, et al. Immunohistochemistry of primary malignant neuroepithelial tumors of the kidney: a potential source of confusion? A study of 30 cases from the National Wilms Tumor Pathology Study Center. Hum Pathol. 2007;38:205–211. 10. Tagarelli A, Spreafico F, Ferrari A, et al. Primary renal soft tissue sarcoma in children. Urology. 2012;80:698–702.

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11. Graham C, Chilton-MacNeill S, Zielenska M, et al. The CIC-DUX4 fusion transcript is present in a subgroup group of pediatric primitive round cell sarcomas. Hum Pathol. 2012;83: 180–189. 12. Moch H, Amin MB, Argani P, et al. Renal cell tumors. Introduction. In: Moch H, Humphrey PA, Ulbright TM, Reuter VE, eds. WHO Classification of Tumors of the Urinary System and Male Genital Organs. Lyon: International Agency for Research on Cancer; 2016:14–17. 13. Argani P, Dehner L, Leuschner I. Mesenchymal tumors occurring mainly in children. In: Moch H, Humphrey PA, Ulbright TM, Reuter VE, eds. WHO Classification of Tumors of the Urinary System and Male Genital Organs. Lyon: International Agency for Research on Cancer; 2016: 54–58. 14. Martignoni G, Cheville J, Fletcher CDM, et al. Mesenchymal tumors occurring mainly in adults. In: Moch H, Humphrey PA, Ulbright TM, Reuter VE, eds. WHO Classification of Tumors of the Urinary System and Male Genital Organs. Lyon: International Agency for Research on Cancer; 2016:59–69.

