What Is Your Diagnosis?

Brittany R. Hyde 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Brianna M. Potter 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Jonathan B. Plenn 2Department of Environmental and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Deanna R. Worley 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.
3Department of Flint Animal Cancer Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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History

A 3.5-year-old 5-kg (11-lb) sexually intact female Affenpinscher was referred for evaluation because of a suspected intrathoracic mass identified on thoracic radiography (Figure 1) performed by the referring veterinarian when evaluating the dog for a 1-day history of coughing, lethargy, and anorexia. Results of hematologic evaluation performed by the referring veterinarian indicated leukocytosis (24,830 WBCs/μL; reference range, 6,000 to 17,000 WBCs/μL) with neutrophilia (22,370 neutrophils/μL; reference range, 3,620 to 12,300 neutrophils/μL), thrombocytosis (553 × 103 platelets/μL; reference range, 117 × 103 to 490 × 103 platelets/μL), hypocalcemia (8.2 mg/dL; reference range, 9 to 12.2 mg/dL), hypoproteinemia (5.3 g/dL; reference range, 5.5 to 7.6 g/dL), and hyperkalemia (5.8 mEq/L; reference range, 3.8 to 5.3 mEq/L). Prior to transferring the dog, the referring veterinarian administered lactated Ringer solution (250 mL total, SC), famotidine (1.0 mg/kg [0.45 mg/lb], IV), and maropitant (1.0 mg/kg, IV). In addition, 17 days earlier, the dog had undergone cesarean section without complication to deliver 3 pups.

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) thoracic radiographic images of a 3.5-year-old 5-kg (11-lb) sexually intact female Affenpinscher referred for evaluation because of a suspected intrathoracic mass identified on thoracic radiography performed by the referring veterinarian when evaluating the dog for a 1-day history of coughing, lethargy, and anorexia. Images published with the permission of Dr. Jasmine Tom, the copyright holder; all rights reserved. Individuals wishing to reproduce the images should contact Dr. Tom at Blue Spruce Animal Clinic, 101 Briscoe St, Castle Rock, CO 80104.

Citation: Journal of the American Veterinary Medical Association 257, 3; 10.2460/javma.257.3.263

On initial referral examination, the dog was tachypneic (60 breaths/min; reference range, 18 to 34 breaths/min), coughed when positioned in lateral recumbency, and had increased respiratory effort, muffled heart sounds, weak femoral pulses synchronous with the heartbeat, and abdominal distension. Signs of mild discomfort were elicited on abdominal palpation.

Formulate differential diagnoses and treatment strategies from the history, clinical findings, and Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretation

Thoracic radiography performed by the referring veterinarian revealed a large, smoothly marginated soft tissue mass that effaced the cranioventral margins of the cardiac silhouette (Figure 2). The mass filled most of the thorax and caused marked dorsal deviation of the trachea. On the ventrodorsal image, the caudal margin of the cardiac silhouette had multiple convex soft tissue bulges that did not typify specific chamber enlargement. The cranial aspect of the mediastinum was widened, and the left cranial lung lobe had an interstitial pattern. There was also evidence of hepatomegaly and decreased abdominal serosal detail. Differential diagnoses included a mass (mediastinal, pericardial, or intrapericardial), pericardial effusion, peritoneopericardial diaphragmatic hernia (PPDH), and dilated cardiomyopathy.

Figure 2—
Figure 2—

Same images as in Figure 1. A large, smoothly marginated soft tissue mass effaces the cranioventral margins of the cardiac silhouette and has multiple convex soft tissue bulges (arrows; A and B) that do not typify specific cardiac chamber enlargement. The trachea is deviated dorsally (asterisk; A), the cranial aspect of the mediastinum is widened (dotted outline; B), and hepatomegaly (arrowhead; A) is evident. Images published with the permission of Dr. Jasmine Tom, the copyright holder; all rights reserved. Individuals wishing to reproduce the images should contact Dr. Tom at Blue Spruce Animal Clinic, 101 Briscoe St, Castle Rock, CO 80104.

Citation: Journal of the American Veterinary Medical Association 257, 3; 10.2460/javma.257.3.263

A focused thoracic ultrasonographic evaluation (not shown) was performed and revealed a large intrathoracic mass that displaced the heart caudally and appeared to compress it. The diaphragm appeared intact, and a mild amount of peritoneal effusion was detected.

Echocardiography with a phased-array 3.0- to 8.0-MHz transducer,a although brief because the dog showed signs of discomfort in lateral recumbency, revealed a large, heterogeneous intrathoracic mass that compressed the right atrium and ventricle (Figure 3). No pericardial effusion was evident, and because a hyperechoic border was present around the cardiac silhouette and considered to have been the pericardium, the mass was suspected to have been extrapericardial. However, owing to the extensiveness of the mass and to the inability to visualize its exact origin, an intrapericardial mass could not be ruled out. Echocardiography also revealed mild tricuspid insufficiency, which was suspected to have been secondary to compression of the right side of the heart by the mass.

Figure 3—
Figure 3—

Right parasternal long-axis 4-chamber 2-D M-mode echocardiographic image of the dog in Figures 1 and 2 showing a hyperechoic border (arrowhead) around the cardiac silhouette (consistent with the pericardium) and a large, heterogeneously echogenic intrathoracic mass (arrow) that is closely associated with the heart. The distance between each dot in the scale along the right of the image is 1 cm. The ECG shows sinus rhythm, with a baseline artifact after the third complex. LV = Left ventricle. RA = Right atrium. RV = Right ventricle.

Citation: Journal of the American Veterinary Medical Association 257, 3; 10.2460/javma.257.3.263

The dog was anesthetized with propofol (4.0 mg/kg [1.8 mg/lb], IV) and fentanyl (0.003 mg/kg [0.001 mg/lb], IV) for thoracic ultrasonography with a 4.8-to 11-MHz linear transducerb and ultrasonographically guided fine-needle aspiration of the mass. A large, heterogeneously echogenic intrathoracic mass in the right hemithorax extended from the thoracic inlet to the diaphragm. The mass caused leftward deviation of the heart and dorsal deviation of the lungs but did not appear to be associated with the pulmonary parenchyma. Color-flow Doppler ultrasonography identified no internal signal of blood flow in the mass, the origin of which was suspected on the basis of findings to have been pericardial or intrapericardial, with a mediastinal origin less likely. The top differential diagnosis was malignant neoplasia, with lymphoma or histiocytic sarcoma highly suspected. Cytologic evaluation of the fine-needle aspirate samples from the mass revealed mesenchymal tissue; however, malignancy could not be determined, and re-aspiration or biopsy was recommended.

To further evaluate the mass and to prepare for surgical or radiation treatment, contrast-enhanced CTc of the thorax was performed. Consistent with findings on ultrasonography, CT revealed a large, smoothly marginated, soft tissue-attenuating mass (precontrast CT [not shown], 14 HU; postcontrast CT [Figure 4], 66 HU) that occupied most of the ventral aspect of the thorax. The mass was closely associated with the cranial and ventral aspects of the heart and caused dorsal and caudal compression of the proximal aspect of cranial vena cava. The myocardium in the region of the right auricle had heterogeneous contrast enhancement, and the right auricle was ill defined. On the basis of CT findings, the mass was suspected to have myocardial or pericardial origin because of its intimate contact with the surface of the heart, and pericardial or intrapericardial neoplasia remained the top differential diagnosis.

Figure 4—
Figure 4—

Midline sagittal (A) and transverse (B) plane postcontrast thoracic CT images of the dog in the previous figures. A large, smoothly marginated mass (66 HU; arrows) occupies most of the ventral aspect of the thorax. The mass is closely associated with the cranial and ventral aspects of the heart (arrowheads). A—Arterial phase image displayed in soft tissue window (window width, 685 HU; window level, 170 HU). The dog's head is to the left of the image, and the dotted vertical line represents the level of the transverse image. B—Venous phase image displayed in soft tissue window (window width, 400 HU; window level, 40 HU), with the dog's right toward the left of the image. LPA= Left lobar pulmonary artery. See Figure 3 for remainder of key.

Citation: Journal of the American Veterinary Medical Association 257, 3; 10.2460/javma.257.3.263

Treatment and Outcome

The dog underwent median sternotomy, and an intrapericardial mass (approx 9 × 6 × 4 cm) that appeared to have originated from the right auricular appendage was resected (Figure 5). Grossly, tumorous tissue was noticed in the stapled pedicle as the mass was resected. The dog recovered from surgery without complication and was discharged after 2 days of being monitored in the hospital. Results of histologic examination of the mass were consistent with a soft tissue sarcoma; however, findings on immunohistochemical staining were inconclusive, with results negative for CD18, CD204, and factor VIII.

Figure 5—
Figure 5—

Intraoperative image showing the dog in the previous figures undergoing median sternotomy and resection of an intrapericardial mass (approx 9 × 6 × 4 cm; arrowhead) that appeared to have originated from the right auricular appendage of the heart. The dog's head is toward the top of the image.

Citation: Journal of the American Veterinary Medical Association 257, 3; 10.2460/javma.257.3.263

Nineteen days after surgery, the dog was returned for suture removal and was reportedly doing well at home. Continued monitoring and radiation therapy for known residual disease were discussed; however, the owner elected active surveillance.

Comments

Thoracic radiography, ultrasonography, and CT combined with echocardiography were all needed in evaluating the dog of the present report; however, CT was the most useful of these modalities in identifying the possible origin of the tumor and in planning surgical treatment. On the basis of physical and radiographic examinations, the initial differential diagnoses in the dog of the present report included a mass (mediastinal, pericardial, or intrapericardial), pericardial effusion, PPDH, and dilated cardiomyopathy. Thoracic ultrasonography and CT helped narrow the likely origin of the mass to pericardial or intrapericardial, with all differential diagnoses being benign or malignant neoplasias. Echocardiography helped rule out cardiomyopathy and, along with transthoracic ultrasonography, ruled out pericardial effusion. Thoracic ultrasonography also helped rule out PPDH and mediastinal mass and was crucial for obtaining fine-needle aspirate samples of the mass. Although the exact origin of the mass could not be determined, results of CT indicated that the mass was associated with either the pericardium or myocardium and that surgical excision could be a treatment option, even if merely palliative.

Cardiac tumors are overall rare in dogs, with primary cardiac tumors being diagnosed more commonly than metastatic tumors.1 The most common primary cardiac tumor in dogs is hemangiosarcoma, followed by aortic body tumors, and with the exception of lymphoma, affected dogs are most commonly between 7 and 15 years old.1,2 Primary cardiac tumors most commonly occur in the right atrium, right auricular appendage, or heart base,1 and treatment options include surgical excision, radiation therapy, and chemotherapy.3 Although many of these masses are not amenable to resection owing to their invasiveness, surgical excision, as was performed in the dog of the present report, can be attempted for treatment of primary cardiac tumors when they occur focally on the right auricular appendage or are circumscribed, such as arising along the right ventricular outflow tract.1,4 Prognosis is largely based on information related to hemangiosarcoma and aortic body tumors,1 with scant data for visceral soft tissue sarcomas, particularly cardiac in origin. For instance, a retrospective study5 of dogs with surgically excised grade II visceral abdominal soft tissue sarcomas shows that the median survival time after surgical intervention was 589 days, and this duration was not dependent on completeness of tumor excision.

Footnotes

a.

EPIQ 7, Philips North American Corp, Andover, Mass.

b.

Aplio 500, Canon Medical Systems USA Inc, Tustin, Calif.

c.

Gemini TF Big Bore PET/CT system, Philips North American Corp, Andover, Mass.

References

  • 1. Burton JH, Stern JA. Neoplasia of the heart. In: Vail DM, Thamm DH, Liptak JM, eds. Withrow and MacEwen's small animal clinical oncology. 6th ed. St Louis: Elsevier Saunders, 2020;787791.

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  • 2. Ware WA, Hopper DL. Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 1999;13:95103.

  • 3. Treggiari E, Pedro B, Dukes-McEwan E, et al. A descriptive review of cardiac tumours in dogs and cats. Vet Comp Oncol 2017;15:273288.

  • 4. Worley DR, Orton EC, Kroner KT. Inflow venous occlusion for intracardiac resection of an occluding right ventricular tumor. J Am Anim Hosp Assoc 2016;52:259264.

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  • 5. Linden D, Liptak JM, Vinayak A, et al. Outcomes and prognostic variables associated with primary abdominal visceral soft tissue sarcomas in dogs: a veterinary society of surgical oncology retrospective study. Vet Comp Oncol 2019;17:265270.

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