How to use pdist2 for unequal vectors?

I want to compute the distance between two vectors by using Jaccard distance measure in matlab program.

I studied about pdist2 function , I used it :

 for i=1:m
 D = pdist2(F(i).tumor,F(i).normal,'jaccard');
 end

the program has this error:

Struct contents reference from a non-struct array object.

Is it important that the vectors in pdist2 sholud be the same size?

I'll be very grateful to have your opinion.