Tumores del estroma gastrointestinal. Diagnóstico por imágenes y correlación anatomopatológica.

Purpose: To describe the imaging features, the anatomic distribution and the surgical, and pathologic (histologic and immunoreactivity) findings of gastrointestinal stromal tumors (GISTs). Material and methods: Thirty nine patients with a diagnosis of GISTs (30 men and 9 women; mean age: 62.5 years old) were studied; they underwent US, CT and MRI studies. All patients were operated on and histologic and immunomarcation examinations were performed. Twenty patients were treated with tyrosine kinase inhibitor (TKI). Follow-up was done in 25 cases. Results: The tumor location in order of frequency was: stomach 26 cases (66.6%), small bowel 9 cases (23.1%) and rectum 4 cases (10.3%). The mean size of the tumors was 12.8 cm, 7 cm and 2.5 cm, respectively. US showed isoechoic solid lesions with a hypoechoic central area in relationship to necrosis or bleeding. The CAT revealed that the peripheral portion (solid) was contrast material enhanced while the central region was not enhanced (hypodense). With the MRI the solid tissue was hypointense in SET1, mild or moderately hyperintense in FSET2, while the central region was notably hyperintense in FSET2. After the contrast material injection the solid region showed a clear enhancement. Tumoral necrosis was observed in 74.5% of all tumors, 12.8% had air in its interior due to fistula, 12.8% was homogeneously solid (4 rectum tumors and one gastric tumor). Only 7/39 cases (17.9%) had metastases. In 19/20 patients (95%) treated with TKI after surgery diagnostic imaging studies showed no local relapse or distant metastases. Conclusion: Diagnostic imaging exams (US, CT, MRI) showed no GIST’s pathognomonic patterns. The immunohistochemical study is required to achieve a final accurate diagnosis which enables a specific treatment.