Clinical, histopathological, and immunohistochemical studies of histiocytic sarcoma in four-toed hedgehogs (Atelerix albiventris): A retrospective study.

Histiocytic sarcoma was investigated histopathologically and immunohistochemically in 17 four-toed hedgehogs (Atelerix albiventris), along with a review of their clinical data. Cases were histopathologically classified into two types: round-polygonal cell type (6 cases) and spindle cell type (11 cases). Round-polygonal cell type was found in visceral organs such as the spleen, lymph nodes, and more, and most cases of this type were consistent with disseminated histiocytic sarcoma. On the other hand, spindle cell type occurred mainly in skin, and almost all cases were consistent with localized histiocytic sarcoma. The prognosis of patients with round-polygonal cell type appeared worse than that of spindle cell type. Immunohistochemically, neoplastic cells of spindle cell type showed stronger reactivity against human leukocyte antigen-DR than round-polygonal cell type. Neoplastic cells of all cases showed strong reactivity against ionized calcium-binding adapter molecule-1 (Iba-1) and various reactivities against cluster of differentiation (CD) 204. Regardless of morphological classification, most tumor cells were negative for CD163, suggesting that this marker is less effective for the diagnosis of histiocytic sarcoma. The results of this study suggest that Iba-1 is the most effective marker for histiocytic sarcoma.