Fixed tissue goes through a series of solutions to prepare the tissue for embedding prior to sectioning. Problems during processing can introduce artifacts into the histologic sections.
Manifestations of poor tissue processing:
(1) The tissue is soft and "boggy" when embedded.
(2) The tissue sections poorly.
(3) The histologic section appears cloudy under the microscope.
(4) Nuclei show variable staining and appear "washed out".
Causes of poor tissue processing:
(1) problems in one or more of the processing solutions, sometimes from overuse
(2) residual water in the tissue when it reaches the clearing solution
(3) excessive heating during the tissue processing
(4) excessive clearing agent present when tissue enters the paraffin bath
(5) incomplete paraffin infiltration
Steps to avoid artifacts:
(1) The alcohols used for processing should not contain excessive water, with the final alcohol solutions anhydrous.
(2) Make sure that the tissue processor is operating properly.
(3) The processing solutions and paraffin should be changed regularly or as needed to avoid contamination.
(4) Make sure that there is adequate temperature control during processing.
(5) Eliminate sources of contamination of the processing solutions, including condensates on container lids.
