Cytology of Canine Malignant Histiocytosis

Abstract

Cytologic features of bone marrow, tissue, and abdominal fluid in seven cases of malignant histiocytosis in dogs are described, and histopathology, hematology, and serum biochemistry of the cases are reviewed. Diagnosis of malignant histiocytosis was confirmed by tissue morphology and immunohistochemistry; neoplastic cells in all cases had positive immunoreactivity to lysozyme. This stain can be used to definitively establish the diagnosis of malignant histiocytosis on cytology specimens as well as tissue sections. Cytologic findings included numerous pleomorphic, large, discrete mononuclear cells with abundant, lightly basophilic, vacuolated, granular cytoplasm. Nuclei were round to oval to reniform with marked anisocytosis and anisokaryosis; nucleoli were prominent. Mitotic figures, often bizarre, were occasionally seen. Multinucleated giant cells and phagocytosis of erythrocytes and leukocytes were prominent features in cytologic preparations in four cases. Four dogs were anemic, five dogs were thrombocytopenic, and three dogs were hypercalcemic. Breeds affected included Doberman Pinscher (1), Golden Retriever (2), Flat Coated Retriever (3), and mixed-breed dog (1).

Morphological Distinction of Histiocytic Sarcoma from Other Tumor Types in Bernese Mountain Dogs and Flatcoated Retrievers

“…In earlier studies, the percentage of tumor cells showing vacuolization in both BMD and FCR was higher (1,7,33,34,38,39,42). However, in human HS, this is reported at a much lower percentage, comparable to the results in our study.…”

“…This has been reported before in canine HS (1,6,7,28,(33)(34)(35)(36)(37)(38)(39) and is also often seen in human HS, sometimes simultaneously with spindle cells (40,41). In addition, extramedullary hematopoiesis was seen more often in BMD than in FCR.…”

Establishment and Biological Characterization of Canine Histiocytic Sarcoma Cell Lines

“…On the other hand, it has been widely accepted that canine HS cells belong to the mononuclear phagocytic system (MPS), including monocytes, macrophages, dendritic cells, and Langerhans cells, because the tumor cells usually contain intracellular microstructures related to phagocytic functions and lysosomal enzymes [2,4,6,7]. However, the exact biological characteristics of HS tumor cells are not clearly understood, because a cell line of HS tumor cells has rarely been established [9,14].…”

“…The diagnosis of HS is based on the pathologic findings, including diffuse proliferation of large anaplastic histiocytes, multinucleated giant cells, and occasional phagocytosis of red blood cells and/or cell debris [2,4,13]. However, a definitive diagnosis is frequently difficult to make due to the presence of infiltrated macrophages and the immature features of tumor cells [5,8].…”

“…However, a definitive diagnosis is frequently difficult to make due to the presence of infiltrated macrophages and the immature features of tumor cells [5,8]. Cytochemical staining, such as with peroxidase and α-naphthyl butyrate esterase, and immunohistochemical staining, such as vimentin, lysozyme, and cytokeratin staining, are considered to be available techniques to diagnose HS [2,3,6,13].…”