Periarticular histiocytic sarcoma with heart metastasis in a cat

Case report: Malignant chemodectoma with hepatic metastasis in a cat

A 10-year-old, male-neutered, domestic short-hair cat was examined at the Veterinary Health Center Emergency Service at Kansas State University for a one-day history of dyspnea. Prior to thoracocentesis, sedation was provided. The cat stopped breathing after sedation and went into cardiac arrest. Cardiopulmonary resuscitation (CPR) was unsuccessful. At necropsy, there was severe pleural effusion and bilateral pulmonary atelectasis. The myocardium of the atria and ventricles, and tunica adventitia of coronary vessels, pulmonary artery, and aorta, had pale, firm, multinodular masses ranging from 0.3 to 0.5 cm in diameter. Multiple nodules were also present in the liver. Multifocally expanding the epicardial fat and compressing the underlying epicardium, infiltrating, and expanding the myocardium, and expanding the walls of major vessels, there was a multinodular, unencapsulated, densely cellular neoplasm composed of polygonal epithelial cells arranged in nests and packets and supported by a fine fibrovascular stroma. The nodules in the liver had similar histologic features. In this case, neoplastic cells at the primary and metastatic sites were intensely immunoreactive to synaptophysin, variably reactive to chromogranin A, and negative for neuron specific enolase, cytokeratin, vimentin, thyroglobulin, and smooth muscle actin. The gross, histologic, and immunohistochemical findings support the diagnosis of chemodectoma, with metastases to the liver. Synaptophysin and chromogranin A were the most useful immunohistochemical markers to diagnose malignant chemodectoma in this cat.

Bilateral renal histiocytic sarcoma with disseminated lung involvement in a Siberian Forest Cat

Case summary

A 5-year-old female neutered Siberian Forest Cat presented with a 7-day history of lethargy, hyporexia and weight loss. Abdominal ultrasonography revealed bilateral renal changes suggestive of neoplasia. Thoracic radiography documented diffuse pulmonary nodules. The cat was euthanased during diagnostic investigations. Histopathological assessment and immunohistochemical staining of post-mortem renal biopsies were consistent with a histiocytic lesion, most likely histiocytic sarcoma (HS). The lung lesions were suspected of representing disseminated disease.

Relevance and novel information

HS is considered a rare neoplastic process in cats. This report describes a case of feline bilateral renal HS with suspected concomitant pulmonary involvement. A primary renal origin was suspected, with the lung lesions being a result of disseminated disease. Renal HS should be included as a differential diagnosis when renal ultrasonography reveals changes suggestive of neoplasia.

Histiocytic sarcoma with central nervous system involvement in 6 cats

Here we characterize 6 cases (4 autopsies and 2 biopsies) of histiocytic sarcoma in the CNS of cats. All affected cats had chronic, progressive clinical signs. Three autopsied cats were euthanized because of a poor prognosis, and one died. The clinical outcome for the biopsy cases remains unknown. Tumors occurred in the brain (4 cases), spinal cord (1 case), and brain and spinal cord (1 case). Neoplasms were restricted to the CNS in 3 cases. Reported gross changes in the 4 autopsy cases consisted of neuroparenchymal swelling with or without tissue pallor or gray discoloration (2 cases) and a yellow or dark-gray mass (2 cases). Histologically, pleomorphic, round-to-elongate neoplastic cells with typical histiocytic morphology effaced the neuroparenchyma and leptomeninges. Multinucleate neoplastic cells were observed in all cases. The mitotic count was 1-24 in 2.37 mm2 (10 FN22 40× fields). Neoplastic cells in all cases had positive immunolabeling for Iba1; immunolabeling was negative for E-cadherin, CD3, CD79, and MUM1, confirming their histiocytic origin.