Thymoma: an immunologic and electron microscopic study.

Ultrastructural features, surface morphology and immunologic surface markers were examined on the cells of three human thymomas. The vast majority of the lymphocytes from the thymomas formed spontaneous rosettes with unsensitized sheep erythrocytes in both cell suspension and frozen tissue section and were, therefore, T cells. In addition to the lymphocytes, epithelial cells and macrophages were observed within the thymomas by transmission electron microscopy. When examined by scanning electron microscopy, most lymphocytes had virtually smooth surfaces, whereas cells believed to be epithelial in origin had surface projections.