OBJECTIVETo study the clinicopathologic features of gastrointestinal stromal tumor (GIST) of small intestine with lymph node metastasis and evaluate the respond to imatinib mesylate (Glivec) therapy.

METHODSTwo cases of GIST of small intestine associated with lymph node metastasis were collected and investigated by light microscopy and immunohistochemistry. Mutation in exon 9, 11 and of c-kit gene were analyzed by polymerase chain reaction and DNA sequencing.

RESULTSThe cases presented as small intestinal mass of irregular shape. Histologically, the tumors consisted of epithelioid and spindled cells, with areas of coagulative necrosis and hemorrhage. The mitotic count measured about 2 per 50 high-power fields. Immunohistochemical study showed that the tumor cells were diffusely distributed and strongly positive for CD117. Mutation analysis revealed that case 1 had an in-frame deletion of 11 amino-acid residues corresponding to 559-569 and carried two missense mutations involving codons 570, 571 in exon 11 of c-kit gene. Case 2 revealed an in-frame deletion involved condons 559-565 in exon 11 of c-kit gene. These two cases were all underwent primary chemotherapy with imatinib mesylate and without new tumor was found during follow-up periods (18, 26 months) after operation.

CONCLUSIONSGIST with nodal metastasis is very rare and needs to be distinguished from other soft tissue sarcomas occurring in this site. The responsiveness to imatinib mesylate therapy correlates with the mutation status of c-kit gene.