Association of ki67 Index with Recurrence in Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GIST) have the potential to recur and metastasize. Several prognostic schemes have been developed but none are precise enough and most times the pathologist faces a small biopsy where it is not possible to evaluate the mitotic count. Our aim was to determine the influence of ki67 index and other clinicopathologic characteristics in the recurrence of GIST.

Forty-three consecutive cases of GIST were studied. The cases presented with non-metastatic disease. We compared the clinicopathologic features of cases with recurrence against those with non-recurrence. The ki67 index was determined by square-millimeters.

The median age was 55 years (IQR 45-63), the most frequent site of involvement was the stomach with 21 (48.8%) cases, and the median of tumor diameter was 10 cm (IQR 5.5-17.5). Twenty-six (60.5%) cases were spindle cell, 13 (30.2%) were mixed, and 4 (9.3%) were epithelioid. The median mitosis count for 50 high power fields was 4 (IQR 0-16), while per square millimeter it was 1 (IQR 0-5, range 0-32). The median of the ki67 proliferation index was 5% (IQR 1-20). During the period of study, 11 (25.6%) patients recurred. The only significant differences between patients with GIST with recurrence and without recurrence were the sex and tumor size.

We did not find an association of the ki67 index with recurrence. The factors associated with recurrence were a high tumor size (> 10 cm) and male sex.