Electron microscopy in the diagnosis of liposarcoma and fibrosarcoma of the larynx.

Electron microscopy (EM) was useful in establishing the final diagnosis in specific instances of liposarcoma and fibrosarcoma of the larynx. In the first case light microscopy revealed cells that met the histologic criteria of a low grade liposarcoma; EM revealed cells that displayed a varied ultrastructural differentiation; thus the tumor was classified as a mixed mesenchymal tumor rather than liposarcoma per se. In the second case, pathologic evaluation indicated a grade 2 fibrosarcoma. EM revealed malignant mesenchymal cells that closely recapitulated normal fibroblasts (no epithelial differentiation was present). This kind of information enables more accurate determination of the source of the primary lesion than results of light microcsopy alone.