Proposed approach for defining risk of aggressive behavior in gastrointestinal stromal tumors

HPF: high powered fields.
* Size represents the single largest dimension. Admittedly this may vary somewhat before and after fixation and between observers. There is a general but poorly defined sense that perhaps the size threshold for aggressive behaviour should be 1 to 2 cm less in the small bowel than elsewhere.
¶ Ideally mitotic count should be standardized according to surface area examined (based on size of high power fields), but there are no agreed definitions in this regard. Despite inevitable subjectivity in recognition of mitoses and variability in the area of high power fields, such mitotic counts still prove useful.