Gastrointestinal stromal tumors-a morphological and immunohistochemical study.

PURPOSE

The rationale of this study was to assess the morphological and immunohistochemical characteristics of gastrointestinal stromal tumor (GIST) along with their risk stratification.

METHODS

Record of 36 cases diagnosed as GIST over a period of 2 years (January 2007 to December 2008) was retrieved. Slides were reviewed for histological typing, immunohistochemical staining, and mitotic count. Cases were divided into very low, low, intermediate, and high-risk groups according to the Fletcher method of risk stratification (Table 1; Fletcher et al. (Int J Surg Pathol 10:81-89, 2002)). Mean, median, and mode were calculated for quantitative variables like age, tumor size, and mitotic count by using SPSS version 14. Frequencies and percentages were also calculated for qualitative variables like results of immunohistochemistry, tumor site, and histological subtypes.

RESULTS

Out of 36 patients, 14 patients were male, and 22 were female. A total of 14 (39%) patients had tumor size between 2 and 5 cm, 13 (36%) patients had size between 5 and 10 cm, and 9 (25%) patients had size >10 cm. There was no tumor less than 2 cm in size. Twenty-one patients (58%) had mitoses <5/50 high power fields (HPF) while seven (20%) had mitoses between 5 and 10/50 HPF and eight (22%) >10/50 HPF. Thirty-one (86%) of cases were strongly positive for CD117 while CD34 was positive in 81% of the cases. Most frequent histological type was hypercellular spindle cell type, and most frequent site of presentation was stomach. Seven patients fell into low risk, ten patients intermediate risk, and 19 patients in high risk groups. There were no patients in very low risk group.

CONCLUSION

By using microscopy and immunohistochemical techniques, GISTs can be diagnosed accurately and treated efficiently. Risk stratification and histological subtyping have emerged as efficient tools to predict malignant behavior.