Electron microscopic observations of benign tumors in oral maxillo facial lesions.

Electron microscopic examinations were made in 20 cases of benign tumor lesions developing in the human lip, buccal mucosa, palate, dorsal area of the tongue and gum. The following findings were obtained. 1) The lumens were observed in pleomorphic adenoma. Microvilli of the tumor cells occurred on the inner side of the luminal wall and the cell organelles were well-developed. 2) The luminal wall of a capillary hemangioma was composed of a single layer of endothelial cells and there were many erythrocytes in the lumen. 3) In the lipoma, a massive proliferation of round fat cells of various sizes had occurred. The nuclei were marginal and lipid droplets in the cytoplasm were almost homogeneous. 4) The cells of the fibroma were spindly or stellate. A well-developed Golgi apparatus and rough surfaced endoplasmic reticulum were observed in the cytoplasm. 5) The cells in the neurilenoma were arranged in a regular pattern, but the cell processes were intertwined and covered with the basement lamina. 6) In the leimyoma many actin filaments and dense paches were observed in the cytoplasm. 7) The cells of the granular cell tumor were enlarged and the nuclei were small. The cytoplasm was filled with many round osmophilic granules. 8) Many Schwann cells and f ibroblasts were observed in the neurof ibroma and mature collageneous fibers were frequently observed in the stroma. 9) A proliferation of collageneous fibers, reticular fibers, capillaries and osteoid figures were observed in the epulis fibromatosa. 10) In the cavernous hemangioma the inner layer of the vascular wall had a saccif orm structure composed of flat endothelium. Edematous structures were observed in the subendothelial area. On the basis of these findings, it can be concluded that transmission and scanning electron microscopic examination is helpful in the differential diagnosis of tumor lesions.