Case study: Primary cardiac lymphoma in a 10-week-old dog
Robert Lo, Ph.D, D.V.M
Canine lymphoma usually appears in multicentric, alimentary, mediastinal, and cutaneous forms, but rarely affects only heart. This case reports a uncommon primary cardiac lymphoma (PCL) of a 10-week-old miniature dachshund. The dog clinically showed acute onset of weakness. Electrocardiography indicated sustained ventricular tachycardia, and thoracic and abdominal radiography revealed pleural and peritoneal effusion. Echocardiography revealed severely hypokinetic left and right ventricles. After failure of treatment, the dog died about 1 hr after admission and underwent autopsy. Gross examination of a longitudinal section through the entire heart revealed poorly demarcated focal or patchy areas of grayish-white tissue infiltrating extensively into the myocardium. Histologically, these lesions were consistent with infiltrative proliferation of neoplastic lymphoid cells. Immunohistochemical staining confirmed the diagnosis of PCL of T-cell origin. There have been no previous reports of such young dogs with PCL.
Fig. 1. Six lead electrocardiographic tracings from the 10-week-old dog, showing monomorphic ventricular tachycardia, rate 360 beats per minute, almost regular (bipolar standard limb leads; 50 mm/sec).
Fig. 2. Formalin-fixed heart transected along the long axis, showing extensive infiltration of grayish-white neoplastic tissue into the myocardium of the entire heart. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. Scale: 1 mm.
Fig. 3. (A) Microscopic section taken from the ventricular septum, showing marked infiltrative proliferation of neoplastic lymphoid cells in the myocardium. Sheets of neoplastic round cells separate individual muscle fibers. HE. Bar: 50 µm. (B) The outlined square area in A is shown at higher magnification. HE. Bar: 20 µm.
Fig. 4. Immunohistochemical labeling of the neoplastic lymphoid cells. Hematoxylin counterstain. Bar: 50 µm. (A) A large number of neoplastic cells stain positively for CD3. (B) Fewer neoplastic cells stain positively for CD79α. (C) All the neoplastic cells are negative for CD20.