Clinical and pathological features of a cardiac chondrosarcoma in a dog

Myocardial Fibrosis with Cartilaginous Tissue Formation in Right Atrial Auricle of a Dog

A 13-year-old castrated male Miniature Dachshund exhibited oedema of the face and cervical region. Clinical examination, including computed tomography, revealed a mass on the right atrial wall. Histopathological examination of the mass revealed proliferation of spindle cells, which formed intersecting bundles and abundant proteoglycan material. Multiple islands of hyaline cartilage were also observed within foci of proliferated spindle cells. Although the proliferated spindle cells replaced the myocardial parenchyma, there was no evidence of malignancy. The spindle cells were immunopositive for vimentin and α-smooth muscle actin, while chondrocytes were immunopositive for vimentin and S100. Neither the spindle cells nor the chondrocytes were immunolabelled for cytokeratin AE1/AE3, desmin, factor VIII, melan A, p63 or Ki-67. These findings indicate that the lesion represented myocardial fibrosis with cartilaginous tissue formation.

Intracardiac Ectopic Thyroid Carcinosarcoma in a Dog

A 13-year-old spayed female Labrador Retriever with a 1-year history of progressive exercise intolerance was diagnosed with an interventricular mass in the heart via echocardiogram. The animal's general condition progressively declined over the next 8 months, and it was euthanatized. The intracardiac mass, which protruded into the lumen of the right ventricle, was removed at necropsy and fixed in 10% buffered formalin. Histopathologic diagnosis was an ectopic thyroid carcinosarcoma based on the presence of 3 distinct neoplastic tissue types. Intermixed within the tumor were neoplastic thyroid follicles containing colloid and solid nests of thyroid follicular epithelial cells, vascular channels and clefts filled with blood and lined by neoplastic endothelium, and osteoid surrounded by spindle cells and often rimmed by large multinucleated cells. Immunohistochemical reaction for thyroglobulin was positive in the tumor cells forming the colloid-filled follicles and solid nests of epithelial cells. Neoplastic endothelium was positive for factor VIII-related antigen. The thyroid gland was located in its normal anatomic position and was histologically normal, ruling out the possibility that the intracardiac tumor was a metastatic lesion. To the authors' knowledge this is the first reported case of an intracardiac ectopic thyroid carcinosarcoma, and possibly the first ectopic thyroid carcinosarcoma in any location in any species.