Peripheral primitive neuroectodermal tumor - pelvis

Case contributed by Dr Fateme Hosseinabadi


Pelvic mass and constipation.

Patient Data

Age: 10 years
Gender: Female

There is a large cystic pelvic mass with a thick enhancing wall, measuring 95*110*108mm at left anterolateral aspect of the rectum and posterior to bladder, cervix and vagina.

Malignant pathologic fracture of L2 vertebrae is noted too (metastasis). Left kidney shows severe hydroureteronephrosis and delayed enhancement.

Histologic findings of PNETs occasionally show spindle cells( MPNST-like), clear cell sarcoma-like foci and rhabdoid cells.

In IHC study, CD99 and Vimentin and neuron specific enolase are positive stains and cytokeratin and desmin are negative stains.

Case Discussion

Peripheral primitive neuroectodermal tumors (PNET) are a highly malignant tumor which usually are found in children and teenagers, and is composed of small round cells of the neuroectoderm. This tumor is categorized in the same family of Ewing sarcomas. There is a translocation in the EWS gene or t(11:22)(q24:q12), and PNETs have a similar histology and IHC and cytogenetics as Ewing sarcomas. Small number of PNETs arising in the pelvis, and are even rarer when located in the extraskeletal pelvis. Its prognosis depends on site of tumor, volume of neoplasm, and metastasis. 20-25% of patients are metastatic when they are diagnosed.

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