[950] Primary Ewing Sarcoma (ES)/Primitive Neuroectodermal (PNET) of the Kidney in Adults – Is Molecular Confirmation Necessary for Treatment?

P Rao, JM Meis. MD Anderson Cancer Center, Houston, TX

Background: ES is a rare primary renal neoplasm that is included in the differential diagnosis of other round cell neoplasms of the kidney. Experience with clinical outcome of these tumors is limited.
Design: We retrieved 13 cases from our archives using the search terms “Ewing sarcoma”, “neuroectodermal tumor” & “kidney" All available slides were reviewed and patients (pts) were divided into 3 groups (Grp).
Results: Grp 1: Cases with molecular confirmation of EWSR1 gene rearrangement (n=6). Mean age at presentation was 38.1 yrs, range 21-56 yrs. Tumor sizes were known in 4 pts; mean 12 cm. Mean follow up (FU) in this group was 12.2 mos, range 4-24 mos. 4 pts were DOD, mean interval to death, 7.7 mos. 1 pt was AWD at 18 mos & 1 pt was lost to FU at 5 months. EWSR1 gene rearrangement was confirmed by FISH in 5 cases &PCR in 1 case. Grp 2: Cases with morphologic features &immunohistochemical evidence of ES but were negative for EWSR1 gene rearrangement by FISH (n=2). Both cases had typical morphologic features of ES. Both pts were female (31 & 32 yrs)& had 12 cm renal masses. 1 patient died of disease 23 mos after diagnosis while the other showed NED at 86 mos. Grp 3: Cases with morphologic &immunohistochemical support for the diagnosis of ES but without molecular confirmation due to current lack of material (n=5). Mean age for this grp was 39 yrs, range 23-52 yrs. FU information was available in 5/6 pts. 3 pts were DOD (mean interval to death 15.6 mos) & 2 pts were AWD at 68 & 3 mos. All pts presented with high stage disease (T3 or T4). The most common site of metastasis was lung (9/12) followed by bone (3/12). Microscopically, tumors were composed of primitive round cells arranged in sheets & lobules. Occasionally tumor cells displayed a more spindled morphology & a prominent pseudopapillary pattern. Mitotic activity &necrosis were prominent. 11/13 cases were positive for CD99. Of the 2 cases that were negative, 1 had a FISH confirmed EWSR1 gene rearrangement.
Conclusions: 1) ES is a rare primary renal neoplasm with a distinct predilection for adults. 2) CD99 is positive in virtually all cases of ES. 3) Molecular testing is a useful adjunct to confirm the diagnosis of ES. However, cases with typical morphologic features in the absence of molecular confirmation are often included in the same group for therapeutic purposes. 4) The majority of cases of renal ES both with & without molecular confirmation seem to have a poor prognosis, unlike those of ES of bone and soft tissue in which prognosis has steadily improved over time.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 168, Tuesday Morning


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