Primary Ewing Sarcoma of the Kidney

Abstract

Primary Ewing sarcoma (ES) of the kidney is rare. We describe the clinicopathologic features of primary renal ES with emphasis on gene fusion partners. A multi-institutional study was conducted to obtain clinicopathologic data on primary ES of the kidney. All tumors with available tissue underwent NGS to determine fusion partners. Twenty-four patients (8 male, 16 female) were identified. Mean age was 33.2 (±12.3). Mean tumor size was 10.5 cm (±4.2). Clinical presentation was available in 21 patients: flank/abdominal pain (13, 61.9%), hematuria (4, 19%), mass (2, 9.5%), hypertension (1, 4.8%), and incidental (1, 4.8%). For 23 nephrectomies, 2 (8.7%) were ypT0 (post-neoadjuvant therapy), 3 (13%) pT1, 15 (65.2%) pT2, 1 (4.4%) pT3, and 2 (8.7%) pT4. Four (16.7%) had metastatic disease at presentation. Of 18 patients with available follow-up, 9 (50%) were alive with disease, 7 (38.9%) alive with no disease, and 2 (11.1%) died of disease (mean follow-up 34 mo). Metastatic disease was documented in 9/18 patients, including lung (3), adrenal (2), bone (2), retroperitoneum (2), liver (2), lymph node (1), and ureter (1). FISH was performed in 14 tumors and real-time quantitative PCR in 1, confirming EWSR1 rearrangements. NGS was performed in 17 tumors, showing EWSR1::FLI1 in 16 (94.1%) and EWSR1::ETV4 in 1. Primary renal ES is a rare neoplasm occurring in a wide age range. Most tumors invaded adjacent tissues. Although they share similar histologic and molecular features with their counterpart in the bone/soft tissue, we document the first case of a rare EWSR1::ETV4 fusion in the kidney.