[Gastrointestinal stromal tumors: current issues]

Gastrointestinal stromal tumours are rare neoplasms originating from the connective tissue of the digestive tract and constitute most of the non-epithelial primitive digestive tumours, with a percentage incidence of less than 1%. The term itself was first used in 1983 by Mazur and Clark to identify a heterogeneous group of tumours, all of them histologically characterised by hyperplastic fused cells, not necessarily leiomuscular ones, but even neural ones. The original stem cell has not been identified yet, but such tumours constantly present the expression of the surface antigens CD34 and CD117 which can be determined immunohisto-chemically. US endoscopy and fine needle aspiration with subsequent immunohistochemical analysis and study of c-kit gene mutation afford the best diagnostic accuracy. Current research is focused mainly on primary cells, probably the cells of Cajal, and on the study of the biological behaviour of gastrointestinal stromal tumours, which can be postulated by assessing several parameters, the most accurate of which seems to be the mitotic index. More recently, the possible therapeutic use of a tyrosine kinase inhibitor has been studied in tumours expressing the c-kit gene. Our experience is based on the histopathological and immunohistochemical study of 11 submucosal tumours (1 liposarcoma, 2 leiomiomas, and 8 gastrointestinal stromal tumours) out of a total of 75 submucosal tumours diagnosed. In the majority of cases a generic diagnosis of submucosal tumour was obtained with oesophagogastro-duodenoscopy and a surgical resection was then performed because of the symptoms. Only in 4 cases was the neoplasm found occasionally in the course of surgery for other reasons. The definitive diagnosis of gastrointestinal stromal tumour, as currently defined, was made only postoperatively by analysis of the histopathological and immunohistochemical findings. In all cases we evaluated the same parameters, i.e. actin, vimentine, S100, CD34, CD117, and Ki67, and confirmed constant high positivity for CD34 and above all for CD117. Even in the absence of unfavourable prognostic indicators, all patients are regularly followed-up.