Tumores del estroma gastrointestinal, definición, generalidades y epidemiología

Gastrointestinal stromal tumours (GIST) are a subgroup of soft-tissue sarcomas which arise from the interstitial cells of Cajal, and express the tirosin kinase receptor CD117. They are the most frequent variety of mesenchymal tumours of the digestive tract, but they hardly represent 1 to 3% of the malignant gastrointestinal neoplasms. Their origin, differentiation line, and molecular behaviour have allowed us to understand their genesis and other neoplasms, as well as establish the molecular target therapy for their treatment. Their estimated prevalence is 15-20 cases per million and it affect to patients at sixty-year old median age. Half of the cases occur in the stomach; this half may also be confined to an specific organ. La Asociacion Mexicana de Cirugia General analyzed 44 cases in a national project attended by 37 researchers. GIST main symptom may be either a painful mass or unspecific symptomatology; nonetheless, bleeding and obstruction must be considered as well. The diagnosis must be histopathologic and its confirmation immunohistochemical: 95% of GIST reacts positively to KIT or CD117. The malignant behaviour of the tumour is determined by its size and the mitosis images. The recurrence-free survival rate, after five years, is 100% for low risk patients; 90% for intermediate, and only 15% for high risk patients. The surgical resective treatment is effective, but 40% of recurrences may occur within two years. Even so, imatinib mesylate (ST1571) selectively inhibits some protein kinases, and it has been administered to patients with advanced tumours since 2000. In 53% of the cases, a 50% tumour regression has been found so far. Resumen Los tumores del estroma gastrointestinal son un subgrupo de sarcomas de tejidos blandos originados de las celulas intersticiales de Cajal, que expresan el receptor de la tirosin-kinasa CD117. Son la variedad mas frecuente de tumores mesenquimatosos del tubo digestivo, pero apenas representan entre el 1 y 3% de las neoplasias malignas gastrointestinales. Su origen, linea de diferenciacion y comportamiento molecular nos han permitido entender la genesis de esta y otras neoplasias, asi como establecer la terapia blanco molecular para su tratamiento. Su prevalencia aproximada es de 15-20 casos por millon y afecta a pacientes de aproximadamente 60 anos; la mitad de los casos ocurren en el estomago; tambien la mitad estan confinados a un organo especifico. La Asociacion Mexicana de Cirugia General analizo 44 casos en un proyecto nacional, en el que participaron 37 investigadores. Los tumores GIST se manifiestan como una masa dolorosa o sintomatologia inespecifica. El sangrado y obstruccion tambien deben ser considerados. El diagnostico debe ser histopatologico y la confirmacion inmunohistoquimica: 95% de los tumores GIST reaccionan positivamente con el KIT o CD117. El comportamiento maligno esta determinado por el tamano del tumor y las figuras de mitosis. La sobrevida a 5 anos libre de recurrencias es de 100% en los pacientes de bajo riesgo; 90% para los de riesgo intermedio y solo 15% para los de alto riesgo. El tratamiento quirurgico resectivo es util, pero suelen presentarse 40% de recurrencias al cabo de dos anos. El Mesilato de Imatinib (STI571), en cambio, inhibe de manera selectiva ciertas protein-kinasas