A large subcutaneous mass was observed at necropsy in the right neck area o
f a 95-week-old female Fischer 344 rat that served as an untreated control
animal in a 2-year carcinogenicity study. Formalin-fixed, paraffin-embedded
sections of the mass were stained with hematoxylin and eosin along with th
e immunohistochemical biomarkers lactoperoxidase, catalase, and amylase. Ba
sed on its histomorphological and immunohistochemical features, the lesion
was diagnosed as a carcinoma of the extraorbital lacrimal gland.