Canine hemophagocytic histiocytic sarcoma: a proliferative disorder of CD11d+ macrophages

Histiocytic disorders of dogs include histiocytoma, localized histiocytic sarcoma (HS), disseminated HS (malignant histocytosis), and the reactive histiocytoses: cutaneous and systemic. A common element to these diseases is proliferation of dendritic cells (DC) of either Langerhans cell (epithelial DC) or interstitial DC lineage. In this report, 17 dogs with hemophagocytic HS are described. Breeds affected included Bernese Mountain Dog (6), Golden Retriever (4), Rottweiler (3), Labrador Retriever (2), a mixed-breed dog, and a Schnauzer, which were from 2.5 to 13 years old. The dogs presented with Coombs negative responsive anemia in 16/17 dogs (94%), thrombocytopenia in 15/17 dogs (88%), hypoalbuminemia in 16/17 dogs (94%), and hypocholesterolemia in 11/16 dogs (69%). All dogs died or were euthanized. The clinical course ranged from 2 to 32 weeks (mean 7.1 weeks). Diffuse splenomegaly with ill-defined masses was consistently present. Microscopic lesions were prevalent in spleen, liver, lung, and bone marrow. Metastasis occurred by insidious intravascular invasion with minimal mass formation. Histiocytes were markedly erythrophagocytic and accompanied by foci of extramedullary hemopoiesis. Cytologically, the histiocytes varied from well differentiated to atypical, with atypia more prevalent in spleen than bone marrow. These tumors arose from splenic red pulp and bone marrow macrophages, which expressed major histocompatibility complex class II and the beta2 integrin, CD11d. They had low and/or inconsistent expression of CD1 and CD11c, which are dominantly expressed by canine nonhemophagocytic HS of DC origin. Canine histiocytic proliferative diseases now encompass proliferation of all members of the myeloid histiocytic lineage: Langerhans cells, interstitial DC, and macrophages.     

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.     

Phagocytic plasmacytoma in a dog

A 4-year-old neutered male Golden Retriever was presented to the oncology service of the North Carolina State University Veterinary Teaching Hospital for staging of a histiocytic sarcoma of the left forelimb, diagnosed on the basis of biopsies submitted by the referring veterinarian. Cytologic assessment of aspirates of 2 splenic nodules identified on ultrasonographic examination of the abdomen revealed a highly phagocytic population of neoplastic round cells morphologically suggestive of plasma cells. Histologic assessment of the forelimb mass after amputation of the limb revealed a neoplastic round cell population demonstrating extensive cytophagia and erythrophagia. Immunohistochemical analysis of the tumor population revealed it to be negative for BLA.36 with sporadic positivity for lysozyme and CD79a. Immunofluorescent evaluation revealed weak tumor cell positivity for immunoglobulin (Ig) A and IgM, but extensive strong positivity for IgG, confirming the plasma cell origin of the tumor. Although extensive phagocytic activity may strongly suggest histiocytic origin, plasma cell origin must also be considered among the differential diagnoses for phagocytic round cell tumors.     

Prior joint disease is associated with increased risk of periarticular histiocytic sarcoma in dogs

Periarticular histiocytic sarcoma (PAHS) is the most common synovial tumour in dogs and is characterized by aggressive local disease with a high rate of distant metastasis. Previously, an association between PAHS and prior joint disease has been demonstrated in the Bernese Mountain Dog breed and suggested in the Rottweiler. We hypothesized that this association would be present in other breeds and investigated this via a retrospective, case‐controlled analysis. Cases were dogs diagnosed with PAHS of the stifle or elbow. Controls were age, breed and sex‐matched dogs without a diagnosis of histiocytic sarcoma. Diagnosis of prior joint disease was determined based on review of medical records and direct veterinarian and owner communications. Data were evaluated using logistic regression, 2‐sampled t tests, and chi‐squared analysis. Our study population consisted of 28 cases and 46 controls, including Flat‐Coated, Golden and Labrador Retrievers, Rottweilers, English Bulldogs, Shih Tzus, Australian Shepherds, Staffordshire Terriers and mixed breed dogs. Dogs with PAHS were more likely to have prior joint disease in the tumour‐affected joint compared with the control population (odds ratio [OR] = 13.42, P < .0001, 95% confidence interval [CI] = 4.33‐48.63). A total of 88.2% of dogs with stifle PAHS had prior joint disease in their tumour‐affected joint, most commonly cranial cruciate ligament rupture. This study confirms that the previously noted association between prior joint disease and PAHS in Bernese Mountain Dogs also applies to other breeds. Additional studies are needed to further investigate for a causal relationship.     

Localized and disseminated histiocytic sarcoma of dendritic cell origin in dogs

Canine histiocytic proliferative disorders include a wide spectrum of diseases characterized by different biologic behaviors. The etiology and pathogenesis of these diseases are largely unknown. The clinicopathologic, morphologic and immunophenotypic characteristics of canine localized and disseminated histiocytic sarcoma were examined in 39 dogs. Rottweilers, Bernese Mountain Dogs, and retrievers were most commonly affected (79%). Localized histiocytic sarcomas (19 dogs) arose from a single site, and metastatic lesions were observed in draining lymph nodes. Predilection sites were subcutis and underlying tissues on extremities, but tumors occurred in other locations, including spleen, lung, brain, nasal cavity, and bone marrow. Disseminated histiocytic sarcomas (20 dogs), a multisystem disease previously described as malignant histiocytosis, primarily affected spleen, lungs, bone marrow, liver, and lymph nodes. Both localized and disseminated canine histiocytic sarcomas were composed of pleomorphic tumor cell populations. CD1+, CD4-, CD11c+, CD11d-, MHC II+, ICAM-1 +, Thy-1 +/- tumor cells were identified in all snap-frozen samples (31 dogs). This phenotype is characteristic for myeloid dendritic antigen-presenting cell lineage. Hence, canine localized and disseminated histiocytic sarcomas are likely myeloid dendritic cell sarcomas. Dendritic antigen-presenting cells are a heterogeneous cell population with regards to their ontogeny, phenotype, function, and localization. The exact sublineage of the proliferating dendritic antigen-presenting cells involved in canine histiocytic sarcomas remains to be determined. Phenotypic analysis of formalin-fixed tissues from eight dogs was limited by available markers. Morphologic features and the phenotype CD18+, CD3-, and CD79a- were the most useful criteria to indicate likely histiocytic origin.     

Cytology of canine malignant histiocytosis

Cytologic features of bone marrow, tissue, and abdominal fluid in seven cases of malignant histiocytosis in dogs are described, and histopathology, hematology, and serum biochemistry of the cases are reviewed. Diagnosis of malignant histiocytosis was confirmed by tissue morphology and immunohistochemistry; neoplastic cells in all cases had positive immunoreactivity to lysozyme. This stain can be used to definitively establish the diagnosis of malignant histiocytosis on cytology specimens as well as tissue sections. Cytologic findings included numerous pleomorphic, large, discrete mononuclear cells with abundant, lightly basophilic, vacuolated, granular cytoplasm. Nuclei were round to oval to reniform with marked anisocytosis and anisokaryosis; nucleoli were prominent. Mitotic figures, often bizarre, were occasionally seen. Multinucleated giant cells and phagocytosis of erythrocytes and leukocytes were prominent features in cytologic preparations in four cases. Four dogs were anemic, five dogs were thrombocytopenic, and three dogs were hypercalcemic. Breeds affected included Doberman Pinscher (1), Golden Retriever (2), Flat Coated Retriever (3), and mixed-breed dog (1).     

Diffuse leptomeningeal histiocytic sarcoma in the cerebrospinal fluid of 2 dogs

Two adult male castrated dogs were evaluated for progressive paraparesis and ataxia. Neurologic examination showed severe ataxia, delayed proprioceptive placement in the pelvic limbs, pain upon palpation of the lumbar spine as well as facial paresis in one dog, and decreased withdrawal reflex of the pelvic limbs in the other dog. Magnetic resonance imaging (MRI) in both dogs showed diffuse meningeal and intramedullary lesions. However, no evidence of a mass was found. Biopsies could not be performed safely due to the location of the lesions. Cerebrospinal fluid (CSF) examination revealed an inflammatory pleocytosis associated with increased protein concentration and numerous large atypical round cells, often multinucleated. Nuclear fragmentation, micronuclei, and rare atypical mitoses were observed. Immunocytochemistry revealed CD1⁺ and CD11c⁺ staining, which, in concert with the morphology confirmed the diagnosis of histiocytic sarcoma (HS). Euthanasia was elected due to poor prognosis. Histopathologic examination showed diffuse spinal and meningeal infiltration with CD18⁺ neoplastic cells, without any evidence of mass formation, which completed the diagnosis of diffuse leptomeningeal HS involving the brain and the spinal cord. Canine central nervous system (CNS) HS has been seldom reported in the literature, with only isolated cases identified on CSF cytology. The cases reported here are remarkable in describing a diffuse CNS leptomeningeal HS associated with neoplastic cells in the CSF of dogs without a tumor mass. These cases emphasize the potential critical importance of CSF analysis in providing an antemortem diagnosis of neoplasia in neurologic patients.     

The diagnosis and prognosis of synovial tumors in dogs: 35 cases

Although synovial cell sarcoma is reported to be the most common neoplasm of the canine synovium, this retrospective study of 35 canine synovial tumors found that the majority were of histiocytic origin. Five (14.3%) synovial cell sarcomas were identified by positive immunohistochemical staining with antibodies to cytokeratin. Eighteen (51.4%) histiocytic sarcomas were identified by cell morphology and immunohistochemical staining with antibodies to CD18. Six (17.1%) synovial myxomas were identified by histologic pattern. The remaining six (17.1%) synovial tumors represented a variety of sarcomas, including two malignant fibrous histiocytomas (actin positive), one fibrosarcoma, one chondrosarcoma, and two undifferentiated sarcomas. Rottweilers were overrepresented in the histiocytic sarcoma category and Doberman Pinschers were overrepresented in the synovial myxoma category. The average survival time was 31.8 months for dogs with synovial cell sarcoma, 5.3 months for dogs with histiocytic sarcoma, 30.7 months for dogs with synovial myxoma, and 3.5 months for dogs with other sarcomas. Among the dogs with follow-up information available, metastatic disease was detected in 25% of dogs with synovial cell sarcoma, in 91% of dogs with histiocytic sarcoma, in none of the dogs with synovial myxoma, and in 100% of dogs with other sarcomas. Immunohistochemical staining for cytokeratin, CD18, and smooth muscle actin is recommended to make the diagnosis and thereby predict the behavior of synovial tumors in dogs.     

Pectinate ligament dysplasia (PLD) and glaucoma in Flat Coated Retrievers. I. Objectives, technique and results of a PLD survey

Pectinate ligament dysplasia (PLD) in dogs is a congenital ocular abnormality affecting the iridocorneal angle, the presence of which may be associated with adult-onset primary glaucoma. This paper describes the objectives, methods and results of a survey of PLD in Flat Coated Retrievers in the UK, including the technique used for gonioscopic assessment of the degree of PLD. In a random sample of 389 Flat Coated Retrievers, 34.7% were found to have a degree of PLD. In a 'target' sample of 48 Flat Coated Retrievers (close relatives of dogs from the random sample with high degrees of PLD, or dogs presented with primary glaucoma), 83.3% were found to have a degree of PLD. The percentage of animals with a degree of PLD was only 6.0% in a 'control' sample of 100 dogs from other breeds. The relationship between PLD and canine glaucoma is discussed.     

Magnetic resonance imaging and histological classification of intracranial meningiomas in 112 dogs

BACKGROUND: Intracranial meningiomas are the most common primary brain tumors in dogs. Classification of meningiomas by tumor grade and subtype has not been reported, and the value of magnetic resonance imaging (MRI) characteristics for predicting tumor subtype and grade has not been investigated. HYPOTHESIS: Canine intracranial meningiomas are a heterogenous group of tumors with differing histological subtypes and grades. Prediction of histopathological classification is possible based on MRI characteristics. ANIMALS: One hundred and twelve dogs with a histological diagnosis of intracranial meningioma. METHODS: Retrospective observational study. RESULTS: Meningiomas were overrepresented in the Golden Retriever and Boxer breeds with no sex predilection. The incidence of specific tumor grades was 56% benign (Grade I), 43% atypical (Grade II), and 1% malignant (Grade III). Grade I histological subtypes included meningothelial (43%), transitional (40%), microcystic (8%), psammomatous (6%), and angiomatous (3%). No statistically significant (P < .05) associations were found among tumor subtype or grade and any of the MRI features studied. CONCLUSIONS AND CLINICAL IMPORTANCE: Meningiomas in dogs differ from their counterparts in humans mainly in their higher incidence of atypical (Grade II) tumors observed. MRI characteristics do not allow for prediction of meningioma subtype or grade, emphasizing the necessity of histopathology for antemortem diagnosis. The higher incidence of atypical tumors in dogs may contribute to the poorer therapeutic response in dogs with meningiomas as compared with the response in humans with meningiomas.     

IMAGING DIAGNOSIS—CONGENITAL VENOUS ANEURYSM OF THE LEFT EXTERNAL JUGULAR VEIN

Primary congenital jugular vein aneurysms are rare with only one prior report in a canine patient. Herein, we describe an 18-week-old Flat Coated Retriever dog in which ultrasound was used to diagnose a primary congenital external jugular vein aneurysm with concurrent dilatation of the internal jugular vein. The aneurysm was successfully removed and the dog remains disease free 24 months postoperatively. Histopathologic analysis was used to validate the ultrasound-based diagnosis.     

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.     

Comparative immunohistochemical characterization of canine seminomas and Sertoli cell tumors

Primary testicular tumors are the most common causes of cancer in male dogs. Overall, the majority of canine patients should be cured by testicular surgery. However, tumor markers are not well-known in veterinary medicine. We sought to determine using immunohistochemistry whether the combined human testicular tumor markers (placental alkaline phosphatase, OCT3/4, CD30, alpha-fetoprotein, inhibin-alpha, vimentin, c-KIT, and desmin) are expressed in canine seminomas and Sertoli cell tumors (SCTs). We examined 35 canine testicular tumors, 20 seminomas and 15 SCTs. c-KIT was expressed markedly in canine seminomas. Both inhibin-alpha and vimentin were expressed significantly in canine SCTs. The results of this study demonstrate differences and similarities between tumor marker expression of testicular tumors in dogs and humans. All the main markers in current routine use are discussed as well as potential useful markers for benign and malignant tumors, and tumor progression.     

SKELETAL LESIONS OF HISTIOCYTIC SARCOMA IN NINETEEN DOGS

The purpose of this study was to describe the clinical and radiographic findings in dogs with bone lesions secondary to histiocytic sarcoma. Nineteen dogs with radiographically identified bone lesions that were histologically diagnosed as histiocytic sarcoma were assessed. The medical records, all available radiographs and histologic sections were reviewed retrospectively. Dogs were subcategorized into localized or disseminated histiocytic sarcoma groups. Golden Retrievers or Rottweilers greater than 5 years of age, with a history of lameness or neurologic deficits localized to the spinal cord was the most common presentation. Fifteen of 19 dogs had a radiographically detectable soft tissue mass associated with bone destruction. The bone lesions had aggressive characteristics and the sites of involvement included periarticular bones (n = 11), vertebrae (n = 6), proximal humerus (n = 5), and rib (n = 2). Fifteen of 19 dogs had disseminated histiocytic sarcoma, and four had localized histiocytic sarcoma. All Rottweilers had disseminated histiocytic sarcoma. Histiocytic sarcoma should be considered as a differential diagnosis for aggressive periarticular, vertebral, or proximal humeral bone lesions identified on radiographs. The index of suspicion should be increased in greater than 5-year-old Golden Retrievers and Rottweilers when a soft tissue mass is associated with the bone lesion on radiographs or myelography. Bone involvement with histiocytic sarcoma, and the Rottweiler breed, was associated with the disseminated form of the disease.     

Feline progressive histiocytosis

Histiocytic proliferative diseases include reactive and neoplastic proliferations of dendritic cells (DC) or macrophages. Various forms of DC proliferations have been documented in humans and dogs; their etiology is largely unknown. With the exception of a few case reports, histiocytic proliferations have not been characterized in cats. This study summarizes clinical, morphologic, and immunophenotypic features of a feline progressive histiocytosis (FPH) in 30 cats. There was no breed or age predilection. Females were more often affected than males. Solitary or multiple nonpruritic firm papules, nodules, and plaques had a predilection for feet, legs, and face. Lesions consisted of poorly circumscribed epitheliotropic (13/30) and nonepitheliotropic (17/30) histiocytic infiltrates of the superficial and deep dermis, with variable extension into the subcutis. The histiocytic population was relatively monomorphous early in the clinical course. With disease progression, cellular pleomorphism was more frequently encountered. Histiocytes expressed CD1a, CD1c, CD18, and major histocompatibility complex class II molecules. This immunophenotype suggests a DC origin of these lesions. Coexpression of E-cadherin, a feature of cutaneous Langerhans cells, was only observed in 3 cats. FPH followed a progressive clinical course; the lesions, however, were limited to the skin for an extended period of time. Terminal involvement of internal organs was documented in 7 cases. Treatment with chemotherapeutics or immunosuppressive and immunomodulatory drugs was not successful. The etiology of FPH remains unknown. FPH is best considered an initially indolent cutaneous neoplasm, which is mostly slowly progressive and may spread beyond the skin in the terminal stage.     

Tumors of the urogenital system in dogs and cats. Retrospective review of 138 cases

The aim of the study was to estimate the prevalence and localization of different tumors in the urogenital system in dogs and cats in relation to sex, age and breed of animals. The study was performed on tumors or tissue specimens from tumors of the urinary and genital system obtained during surgery from dogs and cats submitted to the Division of Pathological Anatomy, Department of Clinical Sciences Agricultural University of Warsaw from 1998 to 2005. Most tumors of the urogenital system recognized in the present study derived from dogs (94.20%, 130 cases), and only a few cases were obtained from cats (5.79%). Occurrence and localization of urogenital system tumors in present review is similar to findings reported by other authors. Testicular tumors in males, ovarian lesions in females and urinary bladder tumors in both sexes were most commonly recognized. Older dogs were most often affected, animals with nonmalignant tumors were a bit younger than those with malignant lesions. Any obvious breed predilections were found, but terriers were at increased risk for development of transitional cell carcinoma of the urinary bladder and mixed breed and German shepherd for development of testicular neoplasms.     

Dendritic cell leukemia in a Golden Retriever

An 8-year-old castrated male Golden Retriever was evaluated for decreased appetite, lethargy, and labored breathing of 1-week duration. Bilateral pulmonary infiltrates, hepatomegaly, and splenomegaly were present. Results of a CBC revealed marked leukocytosis (62,600/microL; reference interval 4000-15,500/microL) and large numbers of atypical cells (30,700/microL) with abundant cytoplasm. There was no concurrent anemia, neutropenia, or thrombocytopenia. Morphology of the atypical cells was most consistent with a histiocytic origin. Similar cells were identified in bone marrow aspirates, and were morphologically suggestive of the macrophage variant of disseminated histiocytic sarcoma. However, flow cytometry of the abnormal circulating cells revealed CD1c, CD11c, and major histocompatibility complex (MHC) Class II expression without expression of CD11d or lymphoid markers, consistent with myeloid dendritic antigen-presenting cells. At necropsy, the splenic architecture was effaced by neoplastic histiocytes that were also infiltrating lung, liver, an abdominal lymph node, myocardium, an bone marrow. Immunohistochemistry of the splenic neoplastic cells confirmed dendritic cell origin (CD1c+, CD11c+, MHC II+, no expression of CD11d and lymphoid markers). To the authors' knowledge, this is the first report of canine dendritic cell leukemia-in this instance accompanied by marked tissue infiltration.     

Immunocytochemical differentiation of canine mesenchymal tumors in cytologic imprint preparations

BACKGROUND: Immunocytochemical techniques are a potentially valuable diagnostic tool to support cytologic diagnosis in dogs. However, detailed studies of staining patterns and intensity in cytologic specimens of mesenchymal tumor types are lacking. OBJECTIVE: The aim of this study was to evaluate commercially available antibodies against human proteins for use in the characterization of canine tumors of mesenchymal origin in cytologic samples. METHODS: Immunocytochemical staining was performed on air-dried imprint specimens of biopsies obtained from 103 mesenchymal neoplasms and 14 metastatic lesions from 98 dogs. All specimens were stained with anti-cytokeratin AE1/AE3 and vimentin. Based on the histologic diagnosis, tumors of muscle, endothelial, histiocytic, and melanocytic origin also were stained with cell-specific antibodies. Staining intensity was subjectively graded and the percentage of positive tumor cells was estimated. RESULTS: All mesenchymal tumors and metastases, with the exception of mesotheliomas, were vimentin-positive and cytokeratin-negative; mesotheliomas (n=6) were positive for both vimentin and cytokeratin. Tumors of muscle (n=5), endothelial (n=15), and histiocytic (n=18) origin stained moderately to strongly positive in a majority of tumor cells with desmin, von Willebrand factor, and lysozyme, respectively. Malignant melanomas (n=15) had variable staining and a variable percentage of positive cells with Melan-A and S100. CONCLUSIONS: Our results indicate that immunocytochemical staining of canine cytologic specimens is a reliable and sensitive technique that may be of benefit for the differentiation of poorly differentiated mesenchymal tumors and metastases. Additional study is needed to assess the specificity of immunocytochemical stains in mesenchymal tumors.     

Neoplastic pleocytosis in a dog with metastatic mammary carcinoma and meningeal carcinomatosis

Abstract: A 12‐year‐old female spayed Labrador Retriever was presented with a history of seizures and abnormal vocalization. Approximately 1 year before presentation, multiple mammary cysts had been surgically excised. A mammary mass was noted on physical examination, and 2 separate parenchymal brain lesions were found on imaging studies. Cerebrospinal fluid (CSF) collected from the cisterna magna was analyzed, and abnormalities included moderate pleocytosis with atypical discrete round cells that occasionally formed loose clusters. The dog was euthanized, and on necropsy a primary solid mammary carcinoma was identified as well as multiple metastatic foci in the brain with diffuse meningeal involvement. The cells in the CSF had a morphologic appearance similar to the cells in the primary mammary tumor and in the metastatic tumors in the brain. On immunostaining, cells from the primary mammary tumor, the brain tumors, and the CSF expressed cytokeratin. The CSF cells did not express CD18, CD3, or CD79a. A final diagnosis of mammary carcinoma with brain metastasis and meningeal carcinomatosis was made.