Automated variable power cold microwave tissue processing: A novel universal tissue processing protocol without using formaldehyde and xylene

The tissue processing technique is used to preserve the biological structure of tissue samples harvested from biopsy as closely as possible to their in vivo state for the diagnoses and study of disease on the cellular level. This process includes fixation, dehydration, clearing, paraffin infiltration. The protocol follows paraffin block embedding, microtome slicing, staining, and microscope slide studying. Tissue processing is a time-sensitive task as histopathologists must rapidly prevent the decomposition of tissue samples and promptly provide diagnoses on time. However, there are different tissue processing protocols for processing tissues with different types and sizes. Fatty tissues and tissues thicker than 1.5 mm are more susceptible to human errors when choosing a proper tissue processing protocol when preparing separate batches of tissues. In this research, a novel automated variable power cold microwave tissue processor was developed using a universal tissue processing protocol (processing time of 97 min) to simultaneously process all tissue types up to 4 mm in thickness. The tissue processor operated with a relatively smaller number of reagents without formaldehyde or xylene. These materials cause severe health and safety issues for humans and the environment. The quality of healthy and diseased processed tissues (sizes 1×1×1 to 24×15×4 mm) of fatty, thyroid, breast, placenta, skin, prostate, stomach, and bladder was examined under a light microscope by defining MAS (morphology, artifacts, and staining) criteria for evaluating cellular details, tissue arrangement, tissue integrity, stain uptake, and visual distinction of a tissue structure in light microscopy. It was found that the new tissue processor has successfully processed both healthy and diseased fatty and nonfatty tissue samples, while all tissue samples also met MAS criteria. Light microscopy showed outstanding integrity and arrangement in the tissue structures with an excellent visual distinction.