Myelopathy caused by a histiocytic sarcoma in a cat

An eight-year-old, female spayed, domestic shorthair cat presented with a three-week history of progressive general proprioceptive ataxia and upper motor neuron paresis of the hindlimbs. Computed tomography revealed a mediastinal mass invading the vertebral canal with the T1 spinal nerve and roots, causing extramedullary compression of the cranial thoracic spinal cord. Histopathological and immunohistochemical studies of the mass during postmortem examination disclosed a neoplasm, later determined to be a poorly differentiated histiocytic sarcoma. Feline histiocytic tumours are rare, with only two prior reports existing in the veterinary literature. This report details a case work-up and reviews the literature on feline histiocytic diseases and tumours affecting the feline spinal     

Dynamic tracheal collapse associated with disseminated histiocytic sarcoma in a cat

This case report describes an unusual presentation of histiocytic sarcoma in a domestic shorthair cat. Initial investigation revealed a haemodynamically insignificant hypertrophic cardiomyopathy, bronchitis and a mild irregularity of the cervical trachea. The cat's disease progressed over a two-week period. Repeat radiography and tracheoscopy revealed a marked dynamic tracheal collapse associated with a raised plaque-like lesion within the cervical trachea. Subsequent post-mortem examination and histopathology revealed disseminated histiocytic sarcoma involving the trachea and kidneys. This is the first reported case of a histiocytic sarcoma involving the trachea in either dogs or cats.     

Histiocytic sarcoma of macrophage origin in a cat: case report with a literature review of feline histiocytic malignancies and comparison with canine hemophagocytic histiocytic sarcoma

Mild nonregenerative anemia was detected in a 9-year-old neutered male domestic shorthair cat during a routine examination. Bone marrow core biopsy revealed erythroid hyperplasia; however, a specific cause was not identified. Over the next 8 months the anemia progressed, eventually becoming mildly regenerative, and moderate thrombocytopenia developed. On ultrasonographic examination, marked splenomegaly, mild hepatomegaly, and abdominal lymphadenopathy were found. Cytologic evaluation of splenic aspirates revealed increased numbers of mildly to moderately pleomorphic histiocytes that frequently had phagocytosed RBCs, leukocytes, and occasionally platelets. Histopathologic examination of the spleen and liver revealed effacement of splenic architecture by a histiocytic sarcoma (HS), and neoplastic histiocytes in hepatic sinusoids. A second bone marrow aspirate revealed neoplastic infiltration by similar cells. The histiocytes in all tissues were mildly to moderately pleomorphic and markedly erythrophagocytic. The immunophenotype of histiocytes in the spleen was CD1c(-)/CD11b(+)/CD18(+)/MHC-II(+), supporting a macrophage cell lineage. The clinical, pathologic, and immunophenotypic findings in this cat were similar to those in hemophagocytic HSs in dogs. To our knowledge, this is the first report of a HS of purported macrophage phenotype in a cat.     

Pulmonary histiocytic sarcoma in a rabbit

An approximately 8‐year‐old male castrated Dutch rabbit was evaluated for a 6‐day history of respiratory signs, which began as sneezing and progressed to tachypnea with anorexia. On physical examination, tachypnea and pale mucous membranes were noted. Thoracic radiographs revealed a soft tissue pulmonary mass, fine‐needle aspirates of which confirmed a neoplasia with malignant features suspicious for a histiocytic sarcoma. The rabbit was discharged and due to a rapidly deteriorating condition, the owner declined chemotherapy with Lomustine and elected euthanasia of the rabbit. The affected lung was submitted for histopathology. Histologic sections of the lung were characterized by clusters of histiocytic cells and multinucleated giant cells with occasional invasion of blood and lymphatic vessels. The histologic diagnosis was histiocytic sarcoma. To the authors' knowledge, this is the first case report of histiocytic sarcoma in a rabbit. Based on the clinical and radiologic findings in this case, histiocytic sarcoma should be included in the list of differentials for rabbits presenting with respiratory signs and evidence of a pulmonary mass.     

Unusual histiocytic disease in a Somali cat

An 8-year-old Somali cat presented with a 9-month history of inappetence, vomiting and weight loss. The disease progressed to involve neurological signs associated with a mass lesion at the level of the first lumbar vertebra. Histopathology identified the condition as malignant histiocytosis affecting the lungs, stomach, mesenteric lymph nodes, liver, spleen, brain and spinal cord. However, the presentation of this case differs from previously reported cases of malignant histiocytosis, and may therefore represent a variant form of histiocytic disease.     

Canine ocular histiocytic sarcoma

OBJECTIVE: To describe and characterize histiocytic sarcoma (HS) first detected in the eyes of dogs using the large database at the comparative ocular pathology laboratory of Wisconsin (COPLOW). METHODS: Cases diagnosed as HS were selected from the COPLOW database. Slides were reviewed to describe the cellular morphology, localize the tumor within the globe, record the tumor distribution and measure the size of the tumor. Further sections were taken to perform immunohistochemistry for Melan-A, CD18 and S-100, and for ferric iron staining. The following clinical information was recorded: breed, age, gender, laterality, clinical signs upon presentation and follow-up information obtained by response to a mailed survey and phone contact. RESULTS: Twenty-six cases were confirmed as being HS according to the immunohistochemical results (CD18 positive and Melan-A negative). The most prevalent breed was Rottweiler (eight cases), followed by Retriever breeds (seven Golden Retrievers and five Labrador Retrievers). The mean age was 8.61 +/- 2.43 years. There were three intact male, eight castrated male, one intact female and 14 spayed female dogs. In 15 dogs there were no concurrent systemic clinical signs at the time of diagnosis. Sixteen of 19 dogs with follow-up information available died as a result of causes related to the tumor, although only three of them received a necropsy. Survival time varied between 5 days and 6 months after enucleation. Three of the dogs were alive at the time the information was gathered. Mean tumor surface was 0.613 +/- 0.38 cm(2). S-100 was diffusely positive in 10 cases, isolated positive cells were found in 11 cases and five cases were completely negative. Seven of the cases were positive for ferric iron. CONCLUSIONS: Histiocytic sarcoma must be considered in the differential diagnosis of dogs with intraocular masses, especially in Rottweilers and Retriever breeds. Because it carries poor prognosis, it must be distinguished from melanoma. A good discriminator for this purpose in paraffin-embedded tissues is finding CD18-positive cells and no reactivity against Melan-A. S-100 and ferric iron staining does not seem to be useful. Ocular HS is considered to be a manifestation of a systemic disease even when the disease is first recognized in the eye.     

Multifocal cutaneous histiocytic sarcoma in a young dog and review of histiocytic cell immunophenotyping

A 9‐month‐old male Great Dane had progressive generalized nodular dermatopathy for several months. There were > 100 raised, alopecic, firm, painful nodules throughout the skin. Aspirates from several lesions yielded moderate numbers of irregularly round or polygonal to spindle‐shaped cells with mild to moderate anisocytosis and few inflammatory cells, and the cytologic interpretation was proliferation of mesenchymal or histiocytic cells. On histopathologic examination, nodules were composed of densely packed sheets of round to spindle‐shaped cells with mild anisokaryosis and low mitotic activity. Multifocal histiocytic sarcoma with a spindle‐cell pattern was diagnosed based on morphologic features and intense expression of CD18. Additional immunophenotypic analysis on frozen sections of tissue confirmed the diagnosis of histiocytic sarcoma; expression of CD18, CD45, CD1a, CD11b, and CD11c, limited expression of Thy‐1 (CD90) and CD80, and lack of expression of CD4, CD11d, and CD86 indicated that the cells were likely interstitial dendritic cells; a review of reactive and neoplastic dendritic cells is provided. Based on staging, internal organs were not affected. Sequential treatment with lomustine and doxorubicin failed to prevent progression of the cutaneous lesions, and the dog died 3 months after initial diagnosis. At necropsy, a focus of neoplastic cells was present in one lymph node, but except for skin other organs were not involved. The clinical presentation of histiocytic sarcoma may be unusual, and neoplastic cells may lack overt features of malignancy on cytologic and histopathologic examination. In some instances, immunophenotyping is required to differentiate histiocytic sarcoma from other histiocytic disorders.     

Primary gastric histiocytic sarcoma in a dog--a case report

A 12-year-old intact female mixed breed dog was presented for chronic, intermittent vomiting and diarrhoea. On endoscopic examination a protruding mass arising from the mucosal surface of the pyloric region was detected. Cytological and histological examination revealed an accumulation of pleomorphic round/oval phagocytic cells suggesting histiocytic origin. This was confirmed by immunohistochemistry. No extra-gastric involvement was detected on clinical examination or at necropsy. This is the first report of primary gastric histiocytic sarcoma in a dog.     

Clinical prognostic factors in canine histiocytic sarcoma

Canine histiocytic sarcoma (HS) is an aggressive neoplasia with variable clinical course and fatal outcome. The goals of this study were to evaluate a large cohort of canine patients with immunohistochemically confirmed HS and identify clinical prognostic factors. Biopsy submissions to the Michigan State University with tentative HS diagnoses were histologically and immunohistochemically confirmed, medical records collected, and interviews with relevant veterinary clinics conducted. Of 1391 histopathology submissions with a diagnosis containing the word ‘histiocytic’, 335 were suspicious for malignancy, and 180 were consistent with HS and had adequate clinical information recorded. The most commonly represented breeds were Bernese mountain dogs (n = 53), labrador retrievers (n = 26) and golden retrievers (n = 17). Median survival for all dogs in the study was 170 days, and subgroup analysis identified palliative treatment, disseminated HS, and concurrent use of corticosteroids as statistically significant negative factors for survival, in both uni‐ and multi‐variate methodologies.     

Plasma cell sarcoma in a cat

Lytic lesions occurring in conjunction with plasma cell sarcoma (multiple myeloma) have rarely been reported in cats.

A plasma cell sarcoma was diagnosed in a 13 year old castrated male Siamese cat with hind limb paresis resulting from osteolysis of the second lumbar vertebra. Serum electrophoresis showed a monoclonal gammopathy. A uniform population of plasma cells was found in and around the second lumbar vertebra and in the bone marrow of the femora, humeri, pelvis and the fifth lumbar vertebra. The neoplastic cells were identified as IgA and kappa chain specific by direct immunofluorescence.

     

CCNU for the treatment of dogs with histiocytic sarcoma

BACKGROUND: Histiocytic sarcoma is an aggressive neoplasm of dendritic cells that carries a grave prognosis. The efficacy of chemotherapy against this disease is unknown. The purpose of this study was to determine the efficacy of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in dogs with incompletely resected or metastatic histiocytic sarcoma, to describe the clinical characteristics of these dogs, and to identify factors affecting prognosis. HYPOTHESIS: Our hypothesis is that CCNU has activity against canine histiocytic sarcoma and can improve survival in dogs with advanced disease. ANIMALS: Included in analysis are dogs diagnosed with histiocytic sarcoma who had gross measurable or residual microscopic disease and who received CCNU. METHODS: A multi-institutional, retrospective, single-arm cohort study was conducted. Available biopsy samples were tested with an antibody against CD18 when possible to confirm the diagnosis of histiocytic sarcoma. RESULTS: Fifty-nine dogs were treated at 8 institutions. Twenty-three tumor specimens were confirmed to be CD18 positive. Treatment with CCNU at 60 to 90 mg/m2 resulted in an overall response rate of 46% in the 56 dogs with gross measurable disease. All 3 dogs with minimal residual disease experienced tumor relapse but lived 433 days or more after starting CCNU. The median survival of all 59 dogs was 106 days. Thrombocytopenia (< 100,000 platelets/microL) and hypoalbuminemia were found to be negatively associated with prognosis and were predictive of < 1 month survival. CONCLUSIONS AND CLINICAL IMPORTANCE: Results suggest that CCNU is active against canine histiocytic sarcoma and may be useful in the treatment of dogs without negative prognostic factors.     

P-66 Disseminated histiocytic sarcoma in a dog receiving long-term immunosuppressive therapy

Canine cutaneous histiocytoma is a common tumor of young dogs. Nodules are single or multiple, alopecic and well demarcated. We studied 15 young dogs with cutaneous histiocytoma. Cutaneous nodules were cytologically and histologically investigated using routine techniques. The subject for morphometry was the nuclear area of histiocytes. The figures were statistically interpreted (Student's t- test). Cytologically, histiocytes represented the largest population, being large-sized cells. The nucleus:cytoplasm ratio was large with oval or bean-shaped nuclei and a fine arrangement of chromatin. The cytoplasm was discrete and basophilic, or abundant and foamy. Five regressive stages were histologically described. Stage 1 was represented by dermal and hypodermal histiocyte proliferation, covered by an intact, uninfiltrated and atrophic epidermis. Epidermal ulcers and necrotizing foci with neutrophilic, lymphocytic and plasma cell infiltrations occurred in Stages 2, 3 and 4. Stage 5 looked like a chronic dermatitis. In Stage 1, the nuclear area was the smallest (4615 ± 62 pixels) with a small coefficient of variation (14.28%), proving a homogeneous population. Stage 2 histiocytes had a larger and more heterogeneous nuclear area (6116 ± 130 pixels) with a 21.12% coefficient of variation. In Stage 3, the average nuclear area (6431 ± 115 pixels) was larger than that for Stage 2 and had a 19.18% coefficient of variation. There were no significant differences between the nuclear areas of histiocytes from Stages 2 and 3; however, significant differences occurred between Stages 1 and 2, and between Stages 1 and 3.
Funding: Self-funded .     

Disseminated histiocytic sarcoma with peripheral blood involvement in a Bernese Mountain dog

Abstract: A 6‐year‐old Bernese Mountain dog was presented with a history of lethargy and weight loss of 2 weeks duration. On physical examination the dog had pale mucous membranes and tachypnea. Ultrasound examination revealed hepatomegaly, splenomegaly, and mesenteric lymphadenomegaly. Results of a CBC included marked normocytic normochromic nonregenerative anemia, marked thrombocytopenia, and moderate leukocytosis with mild neutrophilia and a large population of unclassified round cells (6.2 × 10³/μL). The unclassified cells occasionally were bi‐ or multinucleated and had variably abundant pale basophilic cytoplasm that contained multiple irregular clear vacuoles and occasionally erythrocytes. Fine needle aspirate specimens of the mesenteric lymph nodes and spleen were composed of a population of round pleomorphic cells with the same features as the circulating cells. On flow cytometric analysis of peripheral blood, the unclassified cells expressed CD18, CD45, CD11c, CD1c, and CD14; immunocytochemical analysis of blood smears also indicated the cells were positive for CD1c, CD1a, and CD11c. The dog died a few hours after referral. The histologic interpretation of samples collected from spleen, liver, and lymph nodes was malignant neoplasia of histiocytic origin. Immunohistochemical staining yielded negative results for CD11d, a marker of red‐pulp macrophages, ruling out hemophagocytic histiocytic sarcoma. Based on clinical and pathologic findings, the final diagnosis was disseminated histiocytic sarcoma (DHS) with peripheral blood involvement. To our knowledge, DHS in a dog with evidence and immunophenotyping of neoplastic cells in peripheral blood has been reported only rarely.     

Histiocytic sarcoma in the tarsus of a cat

A 12-year-old Persian cat was examined for a firm swelling of the right tarsal region and enlargement of the corresponding right popliteal lymph node. Cytologic evaluation demonstrated a population of malignant cells consistent with large cell lymphoma. Necropsy revealed a multi-lobulated subcutaneous mass involving the tarsus with some extension into adjacent deep muscular tissue. Histologically, the mass was composed of round cells with eosinophilic cytoplasm and pleomorphic anisokaryotic nuclei. Evidence of articular and nodal infiltration by these cells was observed. Differential diagnoses included synovial sarcoma and histiocytic sarcoma. Neoplastic cells were negative for cytokeratin, CD79a, and CD3 and positive for CD18, vimentin, lysozyme, and alpha-1-antitrypsin, most consistent with a diagnosis of histiocytic sarcoma. This is the first report of a histiocytic sarcoma involving a joint of a cat. The final diagnosis was based on the light microscopic appearance in combination with the immunohistochemical stains.     

Suspected disseminated histiocytic sarcoma in a 3-year-old Perro de Presa Canario dog

A 3-year-old intact male Perro de Presa Canario dog was presented with acutely inflamed and edematous right hind limb, scrotum, prepuce, and an enlarged left carpus. Two weeks later the dog returned with weight loss, draining tracts in the right hind limb, dermal nodules, a palpable abdominal mass, and uveitis in the left eye. The dog succumbed to his illness 2 days later and a widely disseminated round cell tumor compatible with histiocytic sarcoma was diagnosed following postmortem examination.     

Spontaneous histiocytic sarcoma of the popliteal lymph node in a young sprague-dawley rat

The present report describes a rare case of spontaneous primary histiocytic sarcoma of the popliteal lymph node in a 19-week-old female Sprague-Dawley (SD) rat. At necropsy, a 10 mm-diameter whitish nodule was found at the site of the femoral muscle in the right hindlimb. Histopathologically, the nodule comprised large pleomorphic histiocyte-like cells with abundant eosinophilic or foamy cytoplasm. Multinucleated giant cells, necrotic foci surrounded by palisading arrays of epithelioid histiocyte-like cells and phagocytosis of cell debris or erythrocytes by the neoplastic cells were occasionally observed. Invasion of the tumor cells into the surrounding adipose tissue was found focally, but there were no distal metastases. Immunohistochemically, the neoplastic cells were positive for vimentin, CD68 (ED1) and lysozyme. We concluded that this tumor occurred in the popliteal lymph node, considering the anatomical location of the lesion and the presence of the remnants of lymphoid tissue involved in the tumor.