[Study on gastrointestinal stromal tumors by electron microscopy and immunohistochemistry]

To explore the histogenesis and neural differentiation of gastrointestinal stromal tumor (GIST).

The ultrastructural morphology and neural differentiated antigen expression were studied in 20 cases of GIST using electron microscopy and immunohistochemistry.

All of the 20 cases mentioned were positive for c-kit expression. The ultrastructural features of neural differentiation were observed in 7 cases, while no neural or myogenic differentiation seen in 12 cases. Myogenic differentiation to smooth muscle was observed in one case. The ultrastructural features of neural differentiation included scattered or cluster distribution of dense core granules in cytoplasm and cytoplasmic processes; formation of synaptic construction of cell processes; and neurogenic-like processes. In some cases pinocytotic vesicles under the cell membrane and skenoid fibers were seen. Neural differentiation with dense core granules was seen in one case in benign, one case in borderline and five cases in malignant group. The positive reactivity of neural differentiated antigen NSE, CD99, S-100p and CD56 in cases of the neural differentiation group appeared in seven, seven, five and four cases respectively, which were significantly higher than that of the undifferentiated group.

It's rather difficult to differentiate GIST accompanying with neural differentiation from gastrointestinal autonomic nerve tumor if depending only on its histology and immunophenotype appearance, since many features were overlapping in both tumors. Examination of the neural ultrastructures and neural differentiated antigen in GIST might be helpful to clarify the neural differentiation and potential behavior of GIST.