Abstract

Peripheral primitive neuroectodermal tumor (pPNET), a rare, highly aggressive neoplasm of indetermined histogenesis, occurs typically in the soft tissues of the chest wall and the paraspinal region. Comprehensive diagnostic studies including histological, ultrastructural, immunohistochemical and molecular analyses have been stressed to diagnose this entity. We report a case of primary renal PNET which was incidentally found in a 59-year-old man who presented with generalized weakness for 4 months. He was diagnosed as a non-insulin dependent diabetes mellitus 15 years ago and has been made well by oral therapy. An ill-defined mass, measuring 3.5 3 cm, located in the left kidney and perirenal fat, was incidentally found by ultrasonogram during a renal diabetic examination. The mass was resected because of the unresponsiveness against one-year chemotherapy and radiation therapy. Grossly, a homogeneously solid, gray-white mass, measuring 2.8 1.8 cm, was noted in the mid portion of renal cortex. The mass showed severe adhesion to the perirenal fatty tissue. Microscopically, tumor cells were rather uniform, small round with scanty cytoplasm and often showed rosette formation. Ultrastructurally, they showed membrane-bound dense core granules, measuring 125~150 nm, intercellular junctions and microvillous cytoplasmic projections. The tumor cells were uniformly immunoreactive for neuron-specific enolase and were focally immunoreactive for CD99 (013), chromogranin, synaptophysin and cytokeratin. They were not reactive for S-100 protein, vimentin, Leu-7, leukocyte common antigen, desmin and smooth muscle actin. To our knowledge, this is the smallest renal PNET in literature.

• Keywords: Primitive neuroectodermal tumor (PNET);Ewing's sarcoma;Small round cell tumor;Kidney