Influence of prefixation and fixation times on cellular preservation and epithelial cellularity in filter imprints

Cells from malignant and nonmalignant lesions of the breast were suspended in three different fixatives or in a balanced electrolyte solution (Hank's), stored for varying periods of time, collected on Millipore filters and then imprinted on to clean microslides in order to evaluate the influence of prefixation and fixation time on epithelial cellularity and cellular preservation. The use of a methanol-acetic acid fixative (Esposti's fixative) or 50% isopropanol resulted in good preservation whereas cells prefixed in formaldehyde or 100% isopropanol were poorly preserved. Cells that had not been prefixed (suspended in Hank's solution) showed fair preservation. Eighty-eight percent of the imprints prepared from suspensions of Esposti's fixative were highly cellular, which was significantly better than with Hank's solution (68%), 50% isopropanol (66%), 100% isopropanol (56%) and formaldehyde (33%). The cellularity of the formaldehyde-prefixed imprints differed significantly from the others. There was no influence of storage time on either cellular preservation or epithelial cellularity for any of the investigated solutions.