Comparison of Fixation and Processing Methods for Hairless Guinea Pig Skin Following Sulfur Mustard Exposure

Summary Ten anesthetized hairless guinea pigs [Crl:IAF(HA)BR] were exposed to 10 μl of neat sulfur mustard (HD) in a vapor cup on their skin for 7 min. At 24 h postexposure, the guinea pigs were euthanatized and skin sections taken for histologic evaluation. The skin was fixed using either 10% neutral buffered formalin (NBF), McDowell Trump fixative (4CF-1G), Zenker's formol-saline (Helly's fluid), or Zenker's fluid. Fixed skin sections were cut in half: one half was embedded in paraffin and the other half in plastic (glycol methacrylate). Paraffin-embedded tissue was stained with hematoxylin and eosin; plastic-embedded tissue was stained with Lee's methylene blue basic fuchsin. Skin was also frozen unfixed, sectioned by cryostat, and stained with pinacyanole. HD-exposed skin was evaIuated histologically for the presence of epidermal and follicular necrosis, microblis-ter formation, epidermitis, and intracellular edema to determine the optimal fixation and embedding method for lesion preservation. The percentage of histologic sections with lesions vaned little between fixatives and was similar for both paraffin and plastic embedding material. Plastic-embedded sections were thinner, allowing better histologic evaluation, but were more difficult to stain. Plastic embedding material did not infiltrate tissue fixed in Zenker's fluid or Zenker's formol-saline. Frozen tissue sections were prepared in the least processing time and lesion preservation was comparable to fixed tissue. It was concluded that standard histologic processing using formalin fixation and paraffin embedding is adequate for routine histopathological evaluation of HD skin lesions in the hairless guinea pig.