The light and the electron microscopic observation of desmoplastic small round cell tumor

Objective : This paper was to study the histopathologic and ultrastructural features of desmoplastic small round cell tumor (DSRCT). Methods : Three cases of DSRCT were observed by HE light microscopy and immunohistochemical method, and two of three cases were studied by electron microscopy. Results:The characteristic histological pattern of nests of small undifferentiated cells embedded in a dense fibrous stroma was seen in all of cases. This tumor showed immunohistochemical feature of epithelial, mesenchymal as well as neural multidirectional differentiation. Ultrastructural finding was the presence of paranuclear cytoplasmic aggregates of intermediate filaments, which varied greatly from case 1 to case 2 and within the same tumor. In some cells, they appeared as only small aggregates, while in others they occupied a large portion of the cytoplasm and were often arranged in globular whorls. Conclusion: This tumor has distinctive histopathologic, immunohistochemical and ultrastructural features. The electron microscopy plays an important role in diagnosis and differential diagnosis of these tumors.