What is your diagnosis? Pancytopenia in a dog

Abstract: A 4‐year‐old male, castrated, mixed‐breed dog was presented to the Colorado State University Veterinary Teaching Hospital with a 1‐week history of polyuria, polydipsia, lethargy, fever, inappetence, weight loss, and soft mucoid stool. The dog was depressed and had pale, icteric mucous membranes. Results of a CBC included normocytic, normochromic, nonregenerative anemia, neutropenia, and thrombocytopenia, with 43% blast cells (200/μL), many of which contained fine azurophilic granules. Cytologic evaluation of the bone marrow aspirates revealed mild granulocytic hyperplasia that appeared to be left‐shifted in an apparent maturation arrest. A large population of blast cells comprised 35% of nucleated cells; the blasts had high nuclear to cytoplasmic ratios, deeply basophilic cytoplasm with vacuoles, and prominent nucleoli. Most cells also contained many fine azurophilic granules clustered in the paranuclear region. At necropsy, neoplastic cells were abundant in the bone marrow. Immunohistochemically the cells expressed CD3?, and an oligoclonal T‐cell rearrangement was found. The diagnosis was proliferative disorder of CD3⁺ granular lymphocytes, with associated pancytopenia. Because the blast cells were morphologically similar to myeloblasts and immunohistochemistry was required to confirm the diagnosis, T‐cell lymphoproliferative disease should be considered in dogs with pancytopenia presenting with similar clinical features.     

What is your diagnosis? Vertebral mass in a dog

Abstract: A 1‐year‐old, castrated male, mixed‐breed dog was presented for sporadic episodes of kyphosis, tremors, and vocalizing. On neurologic examination, the lesion was localized to spinal cord segments T3–L3. Magnetic resonance imaging of the spine showed an expansile mass occupying most of the ventral aspect of the spinous process of T6. Fine‐needle aspirates of the mass were examined cytologically. A moderately cellular population of pleomorphic spindle cells and abundant mucinous matrix were observed. The cytologic diagnosis was spindle cell neoplasia, with myxosarcoma and fibrosarcoma as the primary differential diagnoses. The dog was euthanized. Histopathologic evaluation of the mass and surrounding tissue confirmed a low‐grade spindle cell sarcoma, with severe compressive myelopathy and mild neutrophilic inflammation. The neoplastic cells stained positive for mucopolysaccharides with Alcian blue, resulting in a final diagnosis of low‐grade (grade 1) myxosarcoma. Fine‐needle aspiration was useful in making a preliminary diagnosis of myxosarcoma in this case. Myxosarcoma should be included in the differential diagnosis for a vertebral mass in a young dog.     

What is your diagnosis? Marked hyperchloremia in a dog

Abstract: A 5‐year‐old neutered male Cavalier King Charles Spaniel was evaluated for a 3‐week history of progressive paresis. The dog had been receiving potassium citrate capsules to acidify urine for the past 2 years because of an earlier history of urolithiasis. Results of neurologic examination, spinal cord radiography, and magnetic resonance imaging of the skull and spinal cord revealed no lesions that could have accounted for the neurologic signs. The main abnormalities on a clinical chemistry profile were marked hyperchloremia (179 mmol/L, reference interval 108–122 mmol/L) and an anion gap of ?50.4 mmol/L (reference interval 16.3–28.6 mmol/L). Because of the severe hyperchloremia, serum bromide concentration was measured (400 mg/dL; toxic concentration >150 mg/dL; some dogs may tolerate up to 300 mg/dL). Analysis of the potassium citrate capsules, which had been compounded at a local pharmacy, yielded a mean bromide concentration of 239 mg/capsule. Administration of the capsules was discontinued and there was rapid resolution of the dog's neurologic signs. This case of extreme bromide toxicity, which apparently resulted from inadvertent use of bromide instead of citrate at the pharmacy, illustrates the importance of knowing common interferents with analyte methodologies and of pursing logical additional diagnostic tests based on clinical and laboratory evidence, even when a patient's history appears to rule out a potential etiology.     

What is your diagnosis? Hemorrhagic effusion in a dog

Abstract: A 2‐year‐old spayed female, German Shepherd dog was presented to the University of Illinois Veterinary Teaching Hospital with a history of intermittent lethargy. On physical examination, lung sounds were increased. The dog had a mild fever (103.7°F) and mild tachycardia (120 bpm). Thoracic ultrasound revealed a sternal mass and pericardial effusion, both of which were aspirated. On cytologic examination, the pericardial fluid contained a large amount of blood and was interpreted as a hemorrhagic effusion. Nucleated cells consisted mainly of macrophages containing phagocytized RBCs and hemosiderin and many clusters of reactive mesothelial cells. The majority of mesothelial cells contained variable amounts of rod‐shaped brown pigment granules that were suspected to be iron. The granules were positive for Prussian blue and carbol–fuschin, indicative of iron potentially mixed with lipofuscin. The granules stained negatively with Melan A, rhodamine, Hall's, and periodic acid‐Schiff. The iron within the mesothelial cells was likely secondary to hemorrhage, based on the erythrophagia and accumulation of hemosiderin in macrophages. Iron deposition and phagocytic activity in mesothelial cells has been reported previously in humans and rats, but not in dogs.     

What is your diagnosis? Intracranial mass in a dog

Abstract: A 9‐year‐old, spayed female Chihuahua was presented for evaluation of acute, progressive neurologic disease. On physical examination the dog was depressed and laterally recumbent. The dog had marked neutrophilia with a toxic left shift and monocytosis. Using computed tomography with contrast enhancement a large intracranial mass lesion was identified in the rostral portion of the brain. The mass extended from the central thalamic region rostral to the cribiform plate and obliterated the lateral ventricles. A fine needle aspirate of the mass contained moderately pleomorphic polygonal cells with many intranuclear cytoplasmic pseudoinclusions (ICPs). The primary differential diagnosis was meningioma, based on cell morphology and the presence of ICPs. At necropsy, the mass was well‐demarcated, unencapsulated, and densely cellular. Cells were arranged in papillary projections on fibrovascular stalks, and eosinophilic ICPs and nuclear folding were frequently seen. Cavitated areas of necrosis throughout the tumor mass were filled with intact and degenerated neutrophils. The histopathologic diagnosis was malignant papillary meningioma. ICPs are not frequently observed in Wright‐stained cytologic preparations but may be found in many types of neoplasms, including meningiomas.