Background: The histiocytic sarcoma (HS) complex is a set of malignant neoplasms originating from interstitial dendritic cells or macrophages. When it involves macrophages of the splenic red pulp and bone marrow, it is referred to as hemophagocytic histiocytic sarcoma (HHS). HHS behaves more aggressively than HS and is usually fatal. HHS can be diagnosed by cytological and histopathological examination of neoplastic tissue. HHS is confirmed by immunohistochemistry using an anti-CD11d antibody. This neoplasm is often confused with immune-mediated hemolytic anemia or Evans syndrome due to erythrophagocytosis and platelet consumption. The clinical presentation of the animals progresses with evident anemia and thrombocytopenia, leading to signs such as prostration, inappetence, and pale mucosa, making diagnosis challenging and often late. This study aimed to report the clinic-pathological aspects of a canine with atypical hemophagocytic splenic HS.Case: A 4-year-old male Shih-Tzu canine was referred to the Veterinary Hospital with a history of prostration and anorexia. Pale mucous membranes were observed on physical examination. Blood tests revealed non-regenerative anemia, leukopenia, and thrombocytopenia. Serum protein levels were below the reference values for the species in biochemical examinations. Hemoparasitosis was suspected; however, the result of the polymerase chain reaction was negative. Abdominal ultrasound revealed a splenomegaly with heterogeneous parenchyma and a slightly irregular surface, but no visible mass in the spleen. Due to the difficulty of stabilizing the patient, even after successive transfusions, the animal underwent exploratory laparotomy with medial access and posterior splenectomy. Subsequently, the spleen was surgically removed, fixed in 10% buffered formalin, and processed routinely. Macroscopically, it had an irregular reddish-brown capsular surface. Histopathological examination of the spleen revealed a densely cellular neoplasm composed of round to spindle cells (histiocytes) arranged haphazardly in variably sized sheets separating the pre-existing spleen stroma. These histopathological findings were consistent with a histiocytic malignant neoplasm. Immunohistochemical analysis was performed to better define the origin of the histiocytic neoplasm. Neoplastic cells showed positive immunostaining of more than 80% of tumor cells for the CD11d antibody and weak immunostaining for CD11c and lysozyme. The patient survived for less than 30 days after the first hospital visit.Discussion: The diagnosis of HHS was based on the histological characteristics and positive immunostaining of more than 80% of the tumor cells for the CD11d antibody. HHS is an extremely aggressive and rare tumor that affects elderly dogs of any breed. In this study, HHS had atypical histologic characteristics, in which erythrophagocytosis and hemosiderin were not observed within macrophages. HHSs arise from macrophages of the red pulp of the spleen or bone marrow and express the b2 integrin, CD11d, and have low expression of CD1 and CD11c, which are predominantly expressed by non-hemophagocytic HS. The hematological and biochemical changes observed in this case were similar to those described in other dogs with HHS. Treatment of HHS is only palliative. Erlichia ewingii, E. canis, Anaplasma phagocytophilum, A. platys, Borrelia burgdorferi, Dirofilaria immitis, Leishmania infantum and immune-mediated hemolytic anemia are the main differential diagnoses because they cause anemia and thrombocytopenia accompanied by splenomegaly.Keywords: histiocytic sarcoma, spleen, immunohistochemistry, splenectomy, erythrophagocytosis.

Heloize Stein

Mariana Pires Oliveira

Camila Serina Lasta

Juliana Eckert

Juliana Sesana Coradini

Letícia Engelhardt Luz

Emerson Antônio Contesini

Clairton Marcolongo Pereira

ACTA SCIENTIAE VETERINARIAE

ASV 关注的论文涉及疾病预防、临床和内科、病理学、外科、流行病学、免疫学、诊断和治疗程序的各个方面，以及应用的生理学、生物化学、免疫化学、遗传学、细胞和分子生物学的基础研究到兽医领域并作为与公共卫生的接口。提交手稿意味着相同的作品尚未发表，也没有考虑在其他地方发表。稿件应首先在线提交给编辑。没有页面费用，只有提交费。

The journal "Acta Scientiae Veterinariae" focuses on papers covering various aspects of disease prevention, clinical and internal medicine, pathology, surgery, epidemiology, immunology, diagnostic and therapeutic procedures. It also includes fundamental research in applied physiology, biochemistry, immunochemistry, genetics, cellular and molecular biology, aimed at applying these findings to veterinary practice and their interface with public health. Submitted manuscripts must be original works that have not been published elsewhere or considered for publication. Manuscripts should be submitted online to the editor first. There are no page charges, only a submission fee.

《Acta Scientiae Veterinariae》关注的论文涵盖了疾病预防、临床和内科、病理学、外科、流行病学、免疫学、诊断和治疗程序的各个方面。此外，还包括应用生理学、生物化学、免疫化学、遗传学、细胞和分子生物学的基础研究，旨在将这些领域的研究成果应用于兽医实践，并与公共卫生领域相结合。提交的手稿必须是未曾发表的作品，且不应考虑在其他地方发表。稿件应首先在线提交给编辑。期刊不收取页面费用，仅收取提交费。

Acta Scientiae Veterinariae

Atypical Spleen Hemophagocytic Histiocytic Sarcoma in a Dog

The clinic-pathological aspects of a canine with atypical hemophagocytic splenic HS, an extremely aggressive and rare tumor that affects elderly dogs of any breed, are reported.

Category	Quartile
农林科学	4
农林科学, 兽医学	4

Atypical Spleen Hemophagocytic Histiocytic Sarcoma in a Dog

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Journal Info

Category	Quartile
VETERINARY SCIENCES	4