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Paper text:
we report a case of low - risk stomach gastrointestinal stromal tumor ( gist ) which has been under a long - term observation , obtaining from this experience knowledge useful in determining the treatment formula for this disease .
  during the observation for 6 years , no such change as ulcer formation was observed in the appearance of the tumor . the measurement of tumor diameter , however , showed gradual growth of maximum tumor diameter from 2.7 to 5.0 cm .
when the changes in the diameter of tumor during this period is plotted , taking the timeon the horizontal axis and the tumor diameter on the vertical axis , the growth of the tumor can be approximated with a secondary function , making it possible to estimate the developmental period of the gist concerned from the approximated secondary function .
thus , the developmental period in this case was estimated to go back 19 years before the time when it was discovered for the 1 time .
further , it was considered that the coefficient of the secondary function represents the rate of tumor growth , and that comparison with this coefficient contributed to the evaluation of malignancy stage of the gist concerned .
the growth curve predicting the growth of tumor could be depicted by measuring the diameter of the tumor in gist twice or more at an interval of 6 - 12 months with eus , and it was thought that this was utilizable for determining treatment formula for gists .
introduction : we report a case of low - risk stomach gastrointestinal stromal tumor ( gist ) which has been under a long - term observation , obtaining from this experience knowledge useful in determining the treatment formula for this disease.results : during the observation for 6 years , no such change as ulcer formation was observed in the appearance of the tumor . 
 the measurement of tumor diameter , however , showed gradual growth of maximum tumor diameter from 2.7 to 5.0 cm . 
 when the changes in the diameter of tumor during this period is plotted , taking the timeon the horizontal axis and the tumor diameter on the vertical axis , the growth of the tumor can be approximated with a secondary function , making it possible to estimate the developmental period of the gist concerned from the approximated secondary function . 
 thus , the developmental period in this case was estimated to go back 19 years before the time when it was discovered for the 1st time . 
 further , it was considered that the coefficient of the secondary function represents the rate of tumor growth , and that comparison with this coefficient contributed to the evaluation of malignancy stage of the gist concerned.conclusion:the growth curve predicting the growth of tumor could be depicted by measuring the diameter of the tumor in gist twice or more at an interval of 6 - 12 months with eus , and it was thought that this was utilizable for determining treatment formula for gists .