I donot understand what you are trying to do in the code. There are much simpler ways to do it.
By looking in your code i think the error is occuring because your for loop index starts from i=1 and ends at i= 200. When you access i-5 or j-5 it will give error because you are indexing negative values to tumor. SImilarly when your loop reaches end it will try to access 200+5 which is out of bound. So run you for loop from
i=1+5:200-5
&
j=1+5:200-5
Edit:
(tumor(i-5,j-5),tumor(i+5,j+5))
and i think what you are intended to do in this line is accessings tumor's i-5th to i+5th index and j-5th to j+5th index( i.e. total 11x11 elements) . AM i right?
