Gastrointestinal stromal tumours: evaluation of biological and clinical current opinions

: The discovery of c-kit gene mutations and the positivity of its transcription products in gastrointestinal stromal tumours (GISTs) suggest a possible origin from Cajal interstitial cells. The study population consisted of 12 patients with GIST, with a mean age of 67.6 years. Preoperative biopsy was performed in 4 cases and in only 1 case did it prove correct. Mesenchymal tumours were regarded as myogenic when they were positive for desmin, and as neurogenic when they were positive for S-100 protein or specific neural enolase (SNE). Seven out of 12 patients underwent simple tumour excision, while in 2 cases ileal resection was performed; gastric resection, total gastrectomy with D2 lymphadenectomy and left colectomy were carried out in one case each. There were two deaths, both unrelated to the primitive diagnosis. Immunohistochemical studies were positive for CD34 in 58% of the cases, and for CD117 in 83%. The mitotic count was higher than 5/10 HPF in 3 cases. The mean survival was 57 months. The overall survival rate was 66%. We found that good tumour differentiation, small size and a low mitotic index correlate with benign behaviour and a better prognosis. Positivity for CD117, evaluated in all malignant lesions, was slightly lower (83% vs 89%) as compared to the data reported in the literature. Tumours with a high mitotic index (> 5 mitoses/10 HPF) and measuring more than 5 cm in diameter are to be considered malignant.