Renal Neoplasia: Diagnostic Problems and Recently Recognized Entities
Case 8 -
Primitive Neuroectodermal Tumor (Ewing Sarcoma) of the Kidney
John N Eble, M.D.
Holger Moch, M.D.
30-year-old woman presented with persistent abdominal pain.
A large mass was palpable in the right side of the abdomen extending into the pelvis. Computerized
tomography showed an 8 x 7 x 6 cm right renal tumor with regional lymph node enlargement and multiple
lung and skeletal metastases. The patient underwent tumor debulking through nephrectomy. After
radiotherapy and high-dosed chemotherapy the patient is without evidence of recurrent disease 28 months
after therapy. Macroscopic findings: The mass measured in excess of 12 cm
in diameter with replacement of the kidney. Cross-sectional features included a gray to tan surface with
areas of hemorrhage and necroses. A pseudocapsule was present.
Primitive neuroectodermal tumor (Ewing sarcoma) of the kidney
Primitive neuroectodermal tumors (PNET) are highly aggressive neoplasms occurring typically in
children and young adults. More than 20 cases have been reported in the kidney. The diagnosis of renal
PNET must be considered in young patients with advanced disease at presentation. PNETs consist of nests
and sheets of loosely cohesive cells with wide bands of geographic tumor necrosis with perivascular
preservation of viable tumor cells. Mitotic figures are numerous. Entrapment of individual nephrons or
renal tubules is common.
The pathological differential diagnosis of malignant small round cell tumors of the kidney includes
monophasic Wilm's tumor, carcinoid, clear cell sarcoma of the kidney (CCSK), primitive rhabdomyosarcoma,
neuroblastoma, lymphoma and even the small cell variant of osteosarcoma. Differentiation of PNET from
other members of this group is facilitated by immunohistochemical techniques. Antibodies against the
MIC2 gene product, such as 12E7, HBA71 (CD99), and 013 may be of diagnostic
help because they stain tumors of the Ewing's family. However, absence of
CD99 expression does not exclude PNET. Molecular detection of the specific fusion transcripts is an
additional tool in the diagnosis of the Ewing's/PNET tumor family. Molecular detection of the specific
EWS/FLI-1 translocation may be of diagnostic help especially in
Outcome of PNET depends upon the localization and staging of the tumor, age of the patient, histologic
classification, extent of surgical resection and time to treatment. Combination of debulking, high-doses
chemotherapy and radiotherapy has shown good results in patients with renal PNETs with metastatic disease
at presentation. Therefore, exact diagnosis of PNET has important clinical consequences.
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