Histological and immunohistochemical studies on primary intracranial canine histiocytic sarcomas

Abstract

Histiocytic sarcoma is a progressive and fatal malignant neoplasm that mainly occurs in middle- to old-aged dogs. This study describes clinicopathological, histological and immunohistochemical characteristics of intracranial histiocytic sarcomas in 23 dogs. Magnetic resonance imaging and/or computed tomography of the brains revealed that the tumors mainly located in the cerebrum, particularly the frontal lobe. Seizure was a predominant clinical sign in most of the cases. Histologically, the tumor cells were morphologically classified into round/polygonal- and spindle-shaped cell types. There was a significant association between tumor cell types and hemophagocytic activity (P<0.05). However, there was no significant difference in other clinicopathological parameters and mitotic index between the 2 types. Immunohistochemically, tumor cells were strongly positive for HLA-DR, Iba-1 and CD204 in all the 23 cases, for iNOS in 20, for CD163 in 17, for CD208 (DC-LAMP) in 9, for lysozyme in 8 and for S100 in 5 cases. In addition, the Ki67-proliferative index showed range of 0.50–64.33% (Average 26.60 ± 3.81%). These observations suggest that canine primary intracranial histiocytic sarcomas tend to exhibit both dendritic cell and macrophage phenotypes of histiocytic differentiation.

Clinicopathological characteristics of histiocytic sarcoma affecting the central nervous system in dogs

“…This complexity is apparent in our data in which larger populations of primary and disseminated CNS HS were analyzed. Corgis have been reported to have a high frequency of HS affecting tissues outside the CNS and also HS affecting the CNS . Although limited in numbers, these data and ours suggest that CNS HS in Corgis rarely is associated with disseminated disease, although extra‐CNS disease frequently is reported.…”

“…Most extra‐CNS HS are thought to be of myeloid dendritic APC (interstitial dendritic cell) origin based on their immunophenotype . The origin of primary CNS HS in dogs is poorly defined, with conflicting reports of expression of both interstitial dendritic cell and macrophage phenotypes . Definition of dendritic APC and macrophage lineages is complex and controversial and commonly used phenotypic markers (eg, CD1, CD11c, CD11b, CD11d, MHCII) may fail to distinguish dendritic cells from monocytes, macrophages, and even activated microglia, particularly in non‐lymphoid organs .…”

“…The majority of published data about CNS HS relates to primary, localized CNS HS in small case series, with limited availability of defined breed predisposition data . Pembroke Welsh Corgis, Shetland Sheepdogs, Labrador Retrievers, and Golden Retrievers were overrepresented relative to total hospital population in 1 study, and Corgis also were noted at higher frequencies in other uncontrolled studies .…”

“…The majority of published data about CNS HS relates to primary, localized CNS HS in small case series, with limited availability of defined breed predisposition data . Pembroke Welsh Corgis, Shetland Sheepdogs, Labrador Retrievers, and Golden Retrievers were overrepresented relative to total hospital population in 1 study, and Corgis also were noted at higher frequencies in other uncontrolled studies . Central nervous system HS appear to differ from HS in most other organs in the severity of inflammatory infiltrate, but it is unclear whether this inflammatory phenotype is common to all CNS HS or if it is restricted to primary localized disease.…”

Primary brain involvement of disseminated histiocytic sarcoma in a Rottweiler dog - histopathology, ¹⁸F-fluorodeoxyglucose positron emission tomography and 7 T-magnetic resonance imaging findings: a case report

“…In the present case, histiocytic origin could be confirmed by positive expression of CD18 and lack of expression of CD3, CD79a and E-cadherin in the cerebellum, liver, spleen and skin. Although immunophenotypes of intracranial HS have been reported using various markers, cellular origin and histogenesis remain uncertain because of the rarity of this type of tumour (Thongtharb et al 2016;Zanelli et al 2017).…”