OBJECTIVE To compare percentages of mast cells in lymph node (LN) aspirate samples from clinically normal dogs, dogs with allergic dermatologic disease (ADD), and dogs with cutaneous mast cell tumors (MCTs). DESIGN Prospective cross-sectional study. ANIMALS 20 healthy dogs (group 1), 20 dogs with ADD (group 2), and 20 dogs with an MCT on the head or limbs (group 3). PROCEDURES LN aspirate samples were obtained from easily accessible LNs in group 1, affected skin regions in group 2, and the likely draining LN or LNs of the MCT in group 3; the percentage of mast cells was manually determined for each LN. For group 3, LNs were cytologically categorized with a modified version of a published metastasis categorization scheme. RESULTS Median (range) percentage of mast cells in aspirate samples was 0% (0% to 0.1%) for group 1, 0.05% (0% to 0.55%) for group 2, and 0.4% (0% to 77.4%) for group 3. In group 3, 16 LNs (13 dogs) were palpably normal in size; 6 of these had evidence of possible or certain metastasis. Seven LNs (7 dogs) in group 3 were palpably enlarged, and 5 of these had evidence of certain metastasis. CONCLUSIONS AND CLINICAL RELEVANCE This study provided evidence to support the use of a uniform cytologic grading system to further define nodal metastasis in dogs with MCTs as well as estimates of the percentage of mast cells in LN aspirate samples for healthy dogs and dogs with ADD. Palpably normal LNs in dogs with cutaneous MCT may contain metastasis.

The variability in cytologic findings and frequent presence of dysplastic spindloid cells suggest that cytology alone may not be a reliable tool to differentiate degenerate canine disk material from a mesenchymal neoplasm.

Companion dogs have recently been promoted as an animal model for the study of aging due to their similar disease profile to humans, the sophistication of health assessment and disease diagnosis, and the shared environments with their owners. In addition, dogs show an interesting life history trait pattern where smaller individuals are up to twofold longer lived than their larger counterparts. While some of the mechanisms underlying this size and longevity trade-off are strongly suspected (i.e., growth hormone/IGF-I), there are likely a number of undiscovered mechanisms as well. Accordingly, we have completed a large-scale global metabolomic profiling of dogs encompassing a range of sizes and ages from three cities across the USA. We found a surprisingly strong location signal in the metabolome, stronger in fact than any signal related to age, breed, or sex. However, after controlling for the effects of location, tryptophan metabolism emerged as significantly associated with weight of the dogs, with small dogs having significantly higher levels of tryptophan pathway metabolites. Overall, our results point toward novel, testable hypotheses about the underlying physiological mechanisms that influence size and longevity in the companion dog and suggest that dogs may be useful in sorting out the complexities of the tryptophan metabolic network.

An 11-year-old, Black and Tan Coonhound dog was presented with a history of lameness of the right hind leg for 2 months, osteolysis in the right distal femur, a pulmonary mass, and a presumptive diagnosis of osteosarcoma. By cytologic examination, neoplastic melanocytes were noted from fine needle aspirates of the femoral and pulmonary masses. Postmortem examination revealed a disseminated melanoma involving the right femoral bone marrow, lung, multiple lymph nodes, and adrenal gland, with diffuse infiltration of the leptomeninges of the brain and spinal cord. This case report describes a unique presentation of canine melanoma, which in some ways resembles leptomeningeal melanomatosis, a rare human melanoma variant.

Histoplasmosis is one of the most common systemic fungal diseases in cats from the United States. It commonly causes respiratory or disseminated disease and is often associated with one or more cytopenias. Here, we describe 32 cats in which a Histoplasma‐like fungal infection was associated with concurrent hemophagia in at least one sample site, commonly spleen, bone marrow, liver, and/or lymph node. The degree of hemophagia was characterized as moderate or marked in the majority of cases, and in all cases, there was a predominance of phagocytized mature erythrocytes. A few cases also had macrophages with phagocytized erythroid precursors, platelets, and/or neutrophils. Complete blood count results were available for 25 cats, and cytopenias were common (20/25), including solitary anemia (10), anemia and thrombocytopenia (5), solitary neutropenia (2), pancytopenia (2), and anemia and neutropenia (1). Bone marrow samples were only available in a small subset of cases, preventing the further assessment of the causes of the cytopenias. Hemophagocytosis has been previously reported in cats with neoplastic diseases and a cat with calicivirus infection, and likely occurs with other conditions as well, such as hemorrhage or hemolysis. Results of this report suggest that systemic fungal disease is an additional differential to consider when there is hemophagia in a feline cytology sample.

A 6-year-old spayed female Boxer dog was presented to the Louisiana State University Veterinary Teaching Hospital with a 3-week history of ataxia, walking sideways, crossing over of limbs, and dragging her hind feet. She had a repair of her left cranial cruciate ligament approximately 4 months previously with uneventful recovery. There was no history of diarrhea or vomiting. Results of a CBC and urinalysis were unremarkable. The only abnormality noted on serum biochemical profile was mild hypercholesterolemia (296 mg/dL, reference interval [RI] 150-240 mg/dL). Cutaneous and mucosal lesions were not present. Age-related changes were seen on thoracic radiographs. Neurologic examination revealed severe ataxia, worse on the left side, and a left head tilt. She had delayed hopping in the forelimbs and fell when hopped in the rear. No abnormalities were observed on computed tomographic scan of the brain. Magnetic resonance imaging of the brain revealed a lesion involving approximately 50% of the left side of the pons and medulla and extending dorsally to the 4th ventricle. Cerebrospinal fluid (CSF) collected from the atlanto-occipital cistern revealed a total nucleated cell count of 2000/mL (RI o 5/mL) and a total protein of 1898 mg/dL (RI o 30 mg/dL). A cytocentrifuged preparation of CSF was stained with Wright-Giemsa and examined (Figure 1). Figure 1. Cytocentrifuged preparation of cerebrospinal fluid from a dog. Wright-Giemsa, Â 100 objective.

A 10‐year‐old, neutered male, indoor/outdoor domestic shorthair cat was presented for a mass on the right front paw. The mass was treated as an abscess, and despite initial resolution, the mass recurred and ruptured approximately 1 month later. This mass successfully resolved with intense management as an open wound. Several days later, the cat developed vomiting and inappetence, and a new mass was noted on the lateral aspect of the right rear limb. Aspirates from the new mass were submitted for cytologic evaluation and bacterial cultures. Anaerobic and aerobic bacterial cultures were negative. Cytologic evaluation revealed septic neutrophilic inflammation with small rod, cocci, curved, and ring forms of bacteria seen, and Mycoplasma spp. infection was suspected based on the morphology of the bacteria. Polymerase chain reaction followed by gene sequencing revealed 86% similarity for Mycoplasma elephantis. The cat was treated with a fluoroquinolone antibiotic and clinically improved, with resolution of the abscess. This case highlights the importance of recognizing the morphologic appearance of Mycoplasma spp. on cytologic examination to help guide additional testing choices and therapeutic planning.

A 1-year old female spayed German Shepherd dog was evaluated for acute onset of dyspnea. Pyogranulomatous inflammation and green globoid structures were present on aspirates of the affected lung. Impression smears and histopathology confirmed pyogranulomatous pneumonia, with large amounts of lipid corresponding to the green structures noted cytologically, and identified poorly staining bacterial rods within lipid vacuoles. Special stains confirmed the presence of acid-fast bacterial rods, and polymerase chain reaction and DNA sequencing identified the organism as Mycobacterium fortuitum. M. fortuitum pneumonia is well described in humans and has previously been reported in 4 dogs and 1 cat. Lipid was a prominent cytologic and histologic feature, as is often described in humans and in the single feline case report. Additionally, this case highlights the variable cytologic appearance of lipid, as well as Mycobacterium spp, which are classically nonstaining with Wright-Giemsa.