Aspiration cytology of Ewing's sarcoma. Light and electron microscopic correlations.

Fine-needle aspiration biopsy specimens from 15 histologically proven cases of Ewing's sarcoma of the bone were studied by both light and electron microscopy. Large glycogen deposits in the Ewing's sarcoma cells could be easily recognized in smears stained routinely with Diff-Quik (American Scientific Product, McGraw Park, IL). These deposits appeared as punched-out clear spaces in the cytoplasm. Ultrastructurally the tumor cells could be divided into chief cells and dark cells. The chief cells were further categorized based on their nuclear morphologic features into cleaved, noncleaved, and intermediate cells. The dominant cell was noncleaved in eight, cleaved in three, and intermediate in four cases. All five tumors with abundant glycogen were composed predominantly of noncleaved cells. The tumor cells in aspiration material appeared to be irregular in shape, and some had cytoplasmic processes. In one tumor these processes were quite prominent; this caused some difficulty in differentiation from neuroblastoma.