A fourteen year old male neutered domestic short-haired cat presented with a several week history of weight loss. No vomiting, diarrhea, or other clinical signs were noted by the owner. Until three days prior to presentation, an oral steroid had been given. Thickened bowel loops were noted upon abdominal palpation, but not other remarkable findings were found on physical exam. The differential diagnoses were lymphoma, mast cell tumor, adenocarcinoma, or possibly inflammatory bowel disease (IBD). Ultrasound-guided aspirates of the thickened intestines were obtained and five slides were submitted for evaluation.
The five submitted slides were moderate to highly cellular and consisted of a moderate amount of cellular debris, many red blood cells, many extracellular and intracellular bacteria of mixed morphology, and a nucleated cell population predominated by poorly preserved neutrophils, with fewer small to intermediate-sized lymphocytes, macrophages, and many cells found in small to large clusters. These clusters consisted of round to polygonal cells with a small to moderate amount of very basophilic cytoplasm. The nuclei were large, round to oval in shape, and exhibited a coarsely-stippled chromatin pattern and one large central prominent nucleolus. The nuclear to cytoplasmic ratio of these cells was typically low; anisocytosis and anisokaryosis were moderate. Binucleation was occasionally noted. Neutrophils could be found imbedded within many of these basophilic clusters.
The cytologic diagnosis was carcinoma/adenocarcinoma with concurrent septic, neutrophilic inflammation.
Surgery is the next logical step in this case, assuming there is no evidence of pulmonary metastasis on thoracic radiographs. The abdomen could be staged preoperatively with a more comprehensive ultrasound or intra-operatively with evaluation of lesion impression smears by an on-site pathologist or by sending STAT digital images using your microscope and phone camera. The septic, neutrophilic inflammation represents either infection/inflammation +/- abscess formation within the tumor or possibly perforation of the bowel.
No mast cells were found, making mast cell tumor a very unlikely diagnosis. Had lymphoma been the cause of the intestinal thickening, a more numerous, very uniform population of lymphocytes would have been expected, without the presence of epithelial cells with so many malignant criteria.