Stromal tumors of the digestive tract. Prognostic value of mitotic index.

OBJECTIVE

We analyzed the prognostic factors and evaluated the usefulness of mitotic index to predict the behavior of gastrointestinal stromal tumors (GIST).

PATIENTS AND METHODS

Fifty three patients operated on for stromal tumors of the digestive tract were studied retrospectively. Mean follow-up was 6 years. The number of mitosis/10 high power fields was the definitive criterion for classification, regardless of their inmunohistologic differentiation. Twelve tumors had 0 mitoses, 34 from 1 to 9 mitoses, and 7 had > or = 10 mitoses. The survival rate was analyzed and the morphological characteristics and evolution were correlated according to mitotic index.

RESULTS

The incidence of advanced illness was related to the number of mitoses: 29% in the group with 1 to 9 mitoses, and 86% when there were > or = 10 mitoses. The recurrence intervals were 44 and 8 months respectively. No tumor with 0 mitoses evolved aggressively. The survival rate was significantly related (p < 0.001), to the mitotic index. The group with 0 mitoses had a survival rate of 100% after 10 years, those with 1 to 9 mitoses 69% and those with > or = 10 mitoses 14%. The other factors which influenced the prognosis (location, size, local invasion and resection) depended, as well, on the mitotic index.

CONCLUSION

The classification of digestive tract stromal tumors by mitotic index is an efficient method because it distinguishes 3 entities with different biological behavior in the long term.