Primary Mesenchymal Chondrosarcoma in the Pericardium of a Dog

Abstract

hemogram was normal except for a monocytosis (2,820/ ml), a mild lymphopenia (880/ml), and an increase in fibrinogen (500 mg/dl). The chemistry profile was normal except for an increase in alkaline phosphatase (851 IU/liter). Survey thoracic radiographs revealed a greatly enlarged, globoid cardiac silhouette with a small volume of pleural effusion. Moderate hepatomegaly with smooth margination was noted in the abdominal radiographs. Differential diagnoses at this time included benign pericardial effusion, atrial hemangiosarcoma with pericardial hemorrhage, dilated cardiomyopathy and a thoracic or cardiac tumor. An ultrasound-guided fine needle aspirate of the mass was obtained. Wright‐Giemsa-stained fine needle aspirates of the pericardial mass revealed moderate numbers of neoplastic round to spindle-shaped cells that were arranged individually and in small clumps within a lightly stippled, eosinophilic background. These cells were characterized by round to oval nuclei with a high nuclear to cytoplasm ratio, coarse nuclear chromatin pattern, and prominent often multiple nucleoli. Anisokaryosis and anisocytosis was moderate to marked. The cytoplasm was deeply basophilic and some of the cells contained variably sized purple granules. Multinucleated cells were also noted, containing from 2 to more than 100 nuclei (Fig. 1). Amorphous, pink, extracellular material was noted around a few of the cellular clumps. A cytologic interpretation of malignant mesenchymal neoplasia was made. The owners declined further evaluation and the dog was euthanatized. A complete necropsy was performed. Approximately two-thirds of the thoracic cavity was occupied by a large, firm intrapericardial mass that displaced the lungs dorsad and caudad. Incision of the pericardium revealed posterior displacement of the heart by a 14