title: Malignant histiocytosis in a domestic cat: cytomorphologic and immunohistochemical features.
abstract: Malignant histiocytosis (MH) was diagnosed in a 13-year-old neutered male Domestic Shorthair cat on the basis of light microscopic and immunohistochemical findings. Thoracic fluid analysis showed a modified transudate which contained a very few atypical discrete cells. Cytologic and histologic evaluation of mediastinal and splenic masses revealed a pleomorphic population of large, discrete, round cells 10 to 30 micrometers in diameter with marked cellular atypia. Nuclei were oval to reniform, often with prominent, bizarre nucleoli. Multinucleated cells and mitotic figures were commonly seen. Erythro- and leucocytophagia were noted. Immunohistochemistry indicated a scattered positive staining pattern with the histiocytic antigenic marker Mac387 and a minor population of cells showing positive reactivity for lysozyme. This report describes the characterization of MH in a cat and emphasizes that MH should be considered as a differential diagnosis in proliferative disorders of discrete-cells in this species.
authors.affiliation: Department of Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado Sate University, Fort Collins, CO 80523.
authors.forename: R. M.
authors.initials: RM
authors.lastname: Walton
authors.forename: D. E.
authors.initials: DE
authors.lastname: Brown
authors.forename: M. J.
authors.initials: MJ
authors.lastname: Burkhard
authors.forename: K. B.
authors.initials: KB
authors.lastname: Donnelly
authors.forename: A. A.
authors.initials: AA
authors.lastname: Frank
authors.forename: L. A.
authors.initials: LA
authors.lastname: Obert
authors.forename: S. J.
authors.initials: SJ
authors.lastname: Withrow
authors.forename: M. A.
authors.initials: MA
authors.lastname: Thrall