Ewing sarcoma/primitive neuroectodermal tumor of the kidney: two unusual presentations of a rare tumor

Abstract

Only few cases of primary renal Ewing's sarcoma have been reported in the literature to date. We present here two cases of renal ES/PNET with an uncanny presentation. The first case was discovered after the patient presented clinically with irradiating flank pain, mimicking the pain related with kidney stones. The second case had clinical presentation of pulmonary thromboembolism after the patient was involved in an automobilist accident. The tumors were mainly composed of small blue cells which by immunohistochemical were positive for neural markers, and FISH revealed the translocation 22q12 for the EWSR1 gene. The diagnosis of renal primitive neuroectodermal tumor/EWING tumor is very rare and usually involves several different diagnostic techniques. The differential diagnosis is usually broad with frequent overlapping features between the entities. The cases presented in this paper illustrated the difficulties with which routine anatomical pathologist is faced when dealing with rare renal poorly differentiated neoplasm in adults.

Figure 1

Thirty-two-year-old patient, right-sided laparoscopic radical nephrectomy. (a) Gross picture of the right kidney showing an 8.3 cm encapsulated tumor located at the pelvic adipose tissue within the renal capsule. (b) Microscopic photography of the tumor showing tumor cells arranged in solid sheets, tightly packed cords, and trabeculae with variable stroma. Tubular structures (arrow) can be identified in the periphery of the cell nests (HE ×20). (c) High power view of the tumor cells showing uniform small round blue cells with scant cytoplasm, uniform nuclei, and stippled chromatin. Mitotic activity (arrow) was present (HE ×100, oil). (d) The tumor cells were strongly positive for NSE in a cytoplasmic stain (DAB X50). (e) Strong membranous and cytoplasmic stain for CD56 (DAB X50). (f) Ki 67 shows a high proliferation rate index of 30% (DAB X50).

Figure 2

Twenty-one-year-old female. (a) Bivalved right kidney: gross photography showing islands of tan tissue with hemorrhage and necrotic yellow friable areas (center). (b) Microphotography of the right atrial mass removed from the patient showing islands of small blue cells intermixed with necrotic material and blood. (c) The tumor cells showed positive membranous satins for CD99 (DAB X40). (d) Viable tumor cells positive for CD56, note that the necrotic cells are negative (DAB X40). (e) Synapthophysin was positive in the viable neoplastic cells in a cytoplasm dot-like pattern (DAB X40). (f) Fluorescent microphotography: normal cell lacking t(22; q12), a 2-fusion signal pattern is expected to be seen, reflecting the 2 intact copies of EWSR1. In abnormal cell (circle) with t(22; q12), a 1-fusion, 1 green, 1 orange signal pattern will be expected to occur. This confirmed the EWSR1 fusion transcripts in this peripheral primitive neuroectodermal tumor of the kidney.