I am preparing a sample for paraffin fixation, I am using 4% PFA solution for the sample for 12 hours at 4 degrees and then dehydrating the sample with the gradient series of ethanol and xylene, and then fixing the tissue in paraffin. but when i cut the paraffin-embedded tissue with microtome it did not cut properly, good to say the sample was not cut with paraffin. I try this many times but the same result. i am confused whats the reason? kindly guide me should i replace the fixative solution. The PICTURE is also attached. when cut with the sample there, s a hole in place of the sample, without sample paraffin slicing goes well?