[Prognostic factors for gastrointestinal stromal tumors]

Stromal tumors of the gastrointestinal tract (GIST) constitute a group of phenotypically heterogenous mesenchymal neoplasms with uncertain biological behaviour.

We examined 31 cases of paraffin-embedded GIST histologically and immunohistochemically in regard to their proliferation. Mitosis were counted, atypical mitosis were noted. Proliferation was measured immunohistochemically by Ki-S5 expression and cytophotometrically by ploidy. Prognostic factors were evaluated and compared to the clinical behaviour.

Mitosis counts with a mean of 6.43/10 HPF (range: 0-51). Eight atypical mitosis were noted of which five had mitosis counts of 10 or less. Proliferation index determined by Ki-S5 was 9.47% (range: 0-30%). Nineteen tumors were aneuploid. Prognostic unfavorable factors included younger age at diagnosis, male sex, muscular differentiation, higher cellularity and site (stomach VS intestine). KAPLAN-MEIER analysis revealed a statistical significance for Ki-S5 index (p = 0.00268) and ploidy (p = 0.0014). Mitosis counts > 10/10 HPF as well as atypical mitosis were associated with an aggressive biological behaviour.

There are different prognostic factors to determine the prognosis of GISTs., e.g. Ki-S5 index, ploidy, mitosis counts and atypical mitosis. Ki-S5 index seems to be the most reliable.