CASE OF THE WEEK
2019-40 / NOVEMBER 25
(CONTRIBUTOR: LEVENTE KUTHI)
10-year-old girl with 15 cm renal mass and multiple pulmonary metastases. She received neoadjuvant chemotherapy according to the SIOP Umbrella Protocol followed by radical nephrectomy. The immunophenotype was as follows: diffusely positive for vimentin, INI1, CD99, focally positive for cyclin D1, PAX2, S100, and negative for EMA, WT1, AE1/AE3, TLE1, ERG, FLI1, CD56, BCL2, PAX8, desmin. FISH analysis was carried out using EWSR1/FLI1 TriCheck Probe, which identified an EWSR1 rearrangement, but the FLI1 was intact.
Quiz
1. What is the correct diagnosis?
a. Clear cell sarcoma of the kidney
b. Wilms’ tumor
c. Ewing sarcoma
d. Desmoplastic small round cell tumor
e. Synovial sarcoma
1. c
1. Ewing sarcoma
Ewing sarcoma (ES) is the second most common mesenchymal malignancy occurring in childhood and young adults. Infrequently, ES develops in the kidney parenchyma, too. Discriminating between ES and other childhood renal neoplasia is essential, because of the different treatment strategies. Besides, ES of the kidney has a dismal outcome especially with M1 disease. The histological appearance is the same as it is seen in ES cases developed in other organs. Genetically, ES harbors EWSR1 gene rearrangement, and the most common partner is FLI1, although other partner genes were also detected, such as the ERG, ETV1, etc. In our case, there was no FLI1 anomaly by FISH, hence we suppose that the partner gene was different. NGS or RT-PCR were not performed.
The differential diagnostic considerations include other small blue cell tumors. Firstly, Wilms’ tumor is the most common childhood renal tumor. Also, Wilms’ tumor is positive with WT1, cytokeratin, but the CD99 is mostly negative. Clear cell sarcoma of the kidney is another tumor with a poor outcome. Its histological appearance can be variable, and it has no specific immunophenotype. Genetically, clear cell sarcoma of the kidney shows BCOR alterations. Desmoplastic small round cell tumor is extremely rare in the kidney. In this tumor, the cells are positive with WT1, desmin and cytokeratin, and they harbor an EWSR1-WT1 fusion. Synovial sarcoma usually affects young males, and these tumors mostly develops in proximity to the joints. Synovial sarcoma rarely originates from the kidney. Immunohistochemically, synovial sarcoma is positive for CD56, PAX2 and BCL2. In addition, SYT-SSX1/2 can be detected in these tumors.
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Levente Kuthi
Department of Pathology, University of Szeged
kuthi.levente@med.u-szeged.hu
Kidney
Childhood renal neoplasia, Ewing sarcoma, blue tumor