Anatomical Pathology Interesting Case Conference

Discussion:

ESK/PNET(Primary Neuroectodermal tumor) is a rare aggressive renal neoplasm in old children and young adults (predominantly 60% males) involving lymph nodes and metastasizing to lung, bone and liver. It is a genetic disease resulting from a translocation mutation fusing the EWS (chromosome 22) and FLI1 genes (chromosome 11).

It presents as acute flank pain mimicking a renal stone colic, palpable renal mass and +/- hydronephrosis.

Grossly, the kidneys are enlarged and the cut surface shows a friable mass, gray-white in color which can be associated with areas of hemorrhage and necrosis.

Microscopically, small to medium-sized cell arranged in sheets, nests, and trabeculae separated by fine fibrous septa are seen. The tumor cells have rounded to oval uniform nuclei, finely granular chromatin, small nucleoli, and pale-to-clear scanty cytoplasm, exhibiting a Homer-Wright rosette arrangement. It can also be associated with necrosis, hemorrhage and fibrosis.

CD99 +, PAX8 + (80 % cases), FISH testing for the EWSR1 gene shows 80–95% of patients with t(11;22) (q24;q12) rearrangement whereas 5–20% often display EWS-ETS gene mutation. Histologically, EWS and small cell carcinomas can both form Homer–Wright rosettes but gene fusion EWS/FLI1 is used to distinguish them.

It is managed surgically by total or radical nephrectomy followed by adjuvant chemotherapy using vincristine, actinomycin, and cyclophosphamide. However, the overall prognosis and survival of ESK is poor, with an overall survival rate of 5.6 months.