Immunohistochemical detection of possible cellular origin of hepatic histiocytic sarcoma in mice

Disseminated histiocytic sarcoma in a squirrel monkey (Saimiri sciureus)

A 14-years-old squirrel monkey was euthanized due to weakness. Histopathological examination revealed multifocal growth of oval cells with severe atypia in the liver, spleen, and bone marrow. The neoplastic cells were positive for histiocytic markers (Iba1, HLA-DR, CD204). This is the fourth case of histiocytic sarcoma in non-human primates.

Optimum immunohistochemical procedures for analysis of macrophages in human and mouse formalin fixed paraffin-embedded tissue samples

Macrophages are closely related to various diseases and it is therefore important that the properties of macrophages are adequately evaluated in human diseases and mouse disease models. Immunohistochemistry (IHC) of formalin fixed paraffin-embedded (FFPE) samples is a very useful tool for examination of macrophages; however, an adequate IHC protocol is required for the examination of macrophage states. In this study, we assessed various antigen retrieval methods in order to devise the optimal protocols for staining of macrophages with a range of antibodies. Optimum combinations of primary antibodies and antigen retrieval protocols were determined; for example, heat treatment with ethylenediamine tetraacetic acid solution, pH 8.0, was the best procedure for IHC using mouse anti-Iba1 and human anti-CD11b, -CD163, -CD169, -CD204, and -CD206 antibodies. Moreover, we found that the immunoreactivity of sliced tissue sections decreased gradually over time in long term storage but that this immunoreactivity was preserved in storage at -80 °C in a deep freezer. The optimal IHC protocols and storage procedures that were determined in this study should be a useful tool for macrophage research.

Histological and immunohistochemical features of histiocytic sarcoma in four domestic ferrets (Mustela putorius furo)

Four cases of histiocytic sarcoma in domestic ferrets (Mustela putorius furo) are described in the present study. Tumor samples obtained from the abdominal viscera, including the spleen, were submitted for histologic examination. Microscopically, poorly demarcated masses contained numerous round- to pleomorphic-shaped cells with coarsely vacuolated and eosinophilic cytoplasm. Bizarre, binucleated tumor cells and multinucleated giant tumor cells with low phagocytic activity were commonly observed. Immunohistochemically, tumor cells in all of the cases were positive for vimentin, human leukocyte antigen-DR, ionized calcium-binding adapter molecule-1, and lysozyme, but some of them lacked cluster of differentiation (CD)163 or CD208 expression. The survival time after surgical resection was 9 days to 5 months. Histiocytic sarcoma in the ferret is a rare, but highly aggressive, tumor commonly found in the spleen.

Chromosome Condensation 1-Like (Chc1L) Is a Novel Tumor Suppressor Involved in Development of Histiocyte-Rich Neoplasms

Human chromosomal region 13q14 is a deletion hotspot in prostate cancer, multiple myeloma, and chronic lymphocytic leukemia. This region is believed to host multiple tumor suppressors. Chromosome Condensation 1-like (CHC1L) is located at 13q14, and found within the smallest common region of loss of heterozygosity in prostate cancer. Decreased expression of CHC1L is linked to pathogenesis and progression of both prostate cancer and multiple myeloma. However, there is no direct evidence for CHC1L’s putative tumor suppressing role in current literature. Presently, we describe the generation and characterization of Chc1L knockout mice. Chc1L^-/- mice do not develop cancer at a young age, but bone marrow and spleen cells from 8–12 week-old mice display an exaggerated proliferative response. By approximately two years of age, knockout and heterozygote mice have a markedly increased incidence of tumorigenesis compared to wild-type controls, with tumors occurring mainly in the spleen, mesenteric lymph nodes, liver and intestinal tract. Histopathological analysis found that most heterozygote and knockout mice succumb to either Histiocytic Sarcoma or Histiocyte-Associated Lymphoma. Our study suggests that Chc1L is involved in suppression of these two histiocyte-rich neoplasms in mice and supports clinical data suggesting that CHC1L loss of function is an important step in the pathogenesis of cancers containing 13q14 deletion.