Gastrointestinal stromal tumors: the clinical and histopathological presentation of 25 cases

Gastrointestinal Stromal Tumors (GIST) are originated from mesenchymal cells; the mutations in tyrosine kinase (TK) receptors (c KIT/ CD117) contribue to loss of growth control and tumor foramation; the most involved are gastrointestinal organs, and rarely extraintestinal retroperitoneum, mesentery and omentum. They are localised commonly in the stomach (50-60%), followed by small bowel (20-30%), colon-rectum (10%),oesophagus (5%), and other intra-abdominal sites (5%). The anatomic location of the tumors also are associated with different tumoral pathologies and prognosis. Histologically were classified as spindle cells (70%), epithelioid (50%) and mixt(5%); the spindle cell subtype presents as a large mass originating from the stomach/small intestine. These tumors presents KIT and PDGFRA mutations and responds well to imatinibe mesilate therapy, with a better prognosis. The epithelioid subtype is less frequent, there haven’t KIT/ PDGFRA mutations and metastasizes to lymph nodes. Material and Methods: 25 patients were operated and followed between 2002-2015 at GOP Taksim Education and Research Hospital; the median follow time was 3.4 (5 months-13 years). Results: The ratio between F/M was 15/10; average age:60.4(29-82)years. Four tumors were diagnosed incidentally at patients operated for other reasons: gastric cancer, sigmoid volvulus, colon cancer, renal cancer. Twenty two patients were classified according with Fletcher system (3 patients were stage 4). The average of Ki67 of stage 4 patients was 15.6 (7-25), intermediate and high risk patients was 9 (2-25). Ki67 >10% was observed in metastatic GIST and only in 3/9 cases of intermediate cases. Twenty four (96%) patients were operated, one patient with primary liver tumor with invasion to gastric wall and lung metastases is still on follow-up without surgery; this case developed intolerance to Imatinib during the three years of follow-up. All cases classified as high risk and metastatic disease were submited to Imatinib treatment. One of these cases was resected and follow up during 13 years, developed local a reccurence before 5 years, and continue to live without reccurence. Interestingly, in our serie there are two cases of oesophageal GIST, low reported ın literature and two cases of primary liver GIST reported extremly rare; the oesophageal tumors has the bad prognosis reputation because late diagnosis, but our cases were classified as very low risk and they are still in our follow up. Conclusion: We analysed the clinical and pathological characteristics of GIST admitted and treated during the past 13 years; the most common site of tumor origine was stomach; the size, mitotic index and Ki67 values were found high in intermediate, high risk group and metastatic diseases.