A clinicopathologic study on 55 cases of gastrointestinal stromal tumor (GIST)

Objective To investigate the clinicopathologic features of GIST. Method Fifty-five GIST cases were collected. Immunohistochemical assays of vimentin, CD117, CD34, S-100, SMA, desmin, NF were used to study the specimen. Results 69% (38/55) of the tumors located in the stomach, 18% (10/55) in the small intestine. Tumors varied greatly in size, ranging from 0.4 to 40 cm (average 6.7 cm). Morphologic criteria of malignancy are tumor size≥5 cm, mitotic rates≥5/50 HPF and ulcer formation and there were significant differences between the benign and the malignant. Immunohistochemical staining results: CD117 positive in 39 cases(71%), CD34 in 45 cases (82%), S-100 in 19 cases (35%), SMA in 12 cases (22%), vimentin in 32 cases (58%), desmin in 6 cases(11%),and NF in 2/4 (50%). All 13 benign cases were alive on the latest follow-up. In 42 cases of malignancy and potential malignancy, 4 developed metastasis, 13 died. Conclusion (1) GIST occur predominantly in middle-aged and older persons.(2) The main criteria of malignancy of GIST are tumor size≥5 cm, mitotic rates≥5/50 HPF and ulcer formation. (3)Whereas it is difficult to identify true leiomyomas/leiomyosarcomars and neuogenic tumors from GIST, immunohistochemical staining is capable of doing this.