Journal of Veterinary Cardiology (2015) 17, 149e153

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CASE REPORT

Pulmonary edema secondary to a cardiac schwannoma in a dog* Justin D. Thomason, DVM a,*, Gregg Rapoport, DVM a, Tiffany Fallaw, RVT a, Clay A. Calvert, DVM a, Kaori Sakamoto, DVM, PhD b a

Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, 501 DW Brooks Drive, Athens, GA 30602, USA b Department of Pathology, College of Veterinary Medicine, University of Georgia, 501 DW Brooks Drive, Athens, GA 30602, USA Received 3 September 2014; received in revised form 24 January 2015; accepted 27 January 2015

KEYWORDS Congestive heart failure; Mitral regurgitation; Intracardiac mass

Abstract A 4-year-old castrated labrador retriever presented for cardiac evaluation to determine the etiology of cardiogenic pulmonary edema diagnosed 1 month prior. A large pedunculated mass involving the ventral aspect of the mural mitral valve leaflet and the endocardial surface of the left ventricular free wall, resulting in severe mitral regurgitation, was identified on echocardiogram. Histopathology and immunohistochemistry of this mass and other endocardial masses identified at necropsy for S-100 protein were consistent with a diagnosis of schwannoma. To the authors’ knowledge, this is the first case of a benign intracardiac schwannoma described in the left heart of a dog. ª 2015 Elsevier B.V. All rights reserved.

* A unique aspect of the Journal of Veterinary Cardiology is the emphasis of additional web-based images permitting the detailing of procedures and diagnostics. These images can be viewed (by those readers with subscription access) by going to http://www. sciencedirect.com/science/journal/17602734. The issue to be viewed is clicked and the available PDF and image downloading is available via the Summary Plus link. The supplementary material for a given article appears at the end of the page. Downloading the videos may take several minutes. Readers will require at least Quicktime 7 (available free at http://www.apple.com/quicktime/ download/) to enjoy the content. Another means to view the material is to go to http://www.doi.org and enter the doi number unique to this paper which is indicated at the end of the manuscript. * Corresponding author. Current address: Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, USA. E-mail address: [email protected] (J.D. Thomason).

http://dx.doi.org/10.1016/j.jvc.2015.01.006 1760-2734/ª 2015 Elsevier B.V. All rights reserved.

150 A 4-year-old, castrated, 35-kg Labrador retriever was referred to the University of Georgia’s College of Veterinary Medicine for cardiac evaluation to determine the etiology of cardiogenic pulmonary edema diagnosed 1 month prior. The referring veterinarian had treated the patient with maintenance furosemide (1 mg/kg PO q12 h), and he was asymptomatic at the time of presentation. The dog had been adopted 1 year earlier, was current on vaccinations, and was receiving monthly heartworm preventative. He had a history of hypoadrenocorticism and was being managed with monthly desoxycorticosterone pivalate (2.2 mg/kg IM) and prednisone (0.25 mg/kg PO q12 h). There was no other significant medical history. Salient features on physical examination were a heart rate of 120 bpm with a regular rhythm, a grade II/VI left apical systolic heart murmur, a respiratory rate of 48 rpm with eupnea, and normal synchronous pulses. Two-dimensional echocardiographic evaluation revealed a pedunculated nodular mass involving the ventral aspect of the mural mitral valve leaflet and the endocardial surface of the left ventricular free wall (Fig. 1). No effusions or spontaneous echocardiographic contrast were noted. The left atrium appeared severely dilated (absolute left atrial diameter on right parasternal long axis ¼ 54 mm;

J.D. Thomason et al. left atrial to aortic diameter ¼ 2.0). There was incomplete coaptation of the mitral valve apparatus secondary to the intracardiac mass. Subjectively, the left ventricular chamber size was increased and the interventricular septum and left ventricular free wall were mildly decreased in thickness. Left ventricular wall motion appeared normal. All other cardiac structures appeared subjectively normal. Color-flow Doppler evaluation revealed severe mitral regurgitation, trivial tricuspid regurgitation, trivial pulmonic regurgitation, trivial aortic regurgitation, laminar flow within the left ventricular outflow tract, and laminar flow within the right ventricular outflow tract. Other findings included a normal sinus rhythm throughout the echocardiogram, mildly increased preload (as assessed by peak velocity of early diastolic transmitral flow to peak velocity of late transmitral flow, peak velocity of early diastolic transmitral flow to peak velocity of early diastolic mitral annular motion, peak velocity of early transmitral flow to isovolumic relaxation time, and deceleration time of the early diastolic transmitral flow velocity) and a systolic blood pressure of 100 mmHg. Differential diagnosis for the intracardiac mass included neoplasia, thrombus and infective endocarditis. Given the appearance of the mass, history of normal complete blood counts, and absence of

Figure 1 Transthoracic echocardiogram recorded from the right parasternal long axis view. A pedunculated nodular mass involving the ventral aspect of the mural mitral valve leaflet and the endocardial surface of the left ventricular free wall is present. Due to severe mitral regurgitation (not evident on image), severe left atrial and ventricular dilation is present.

Cardiac schwannoma in a dog

Figure 2 H & E Stain (200). The neoplasm is composed of spindle cells forming streams, bundles, and palisades. These cells are elongated, with moderate amounts of eosinophilic, fibrillar cytoplasm, and oval to polygonal nuclei, with finely to coarsely stippled chromatin, and inapparent nucleoli.

pyrexia, neoplasia and thrombus were entertained as likely possibilities. Hemostatic assays, including thromboelastography and D-dimers were normal suggesting against the diagnosis of thrombus. Therapeutic recommendations at that time were: furosemide (0.9 mg/kg PO q12 h), enalapril (0.4 mg/kg PO q12 h), pimobendan (0.3 mg/kg PO q12 h). Surgical mass resection was offered to the client but was declined. Serial monitoring, every 3e6 months or sooner if sleeping respiratory rate >8 respirations per 15 s, was recommended. Serial echocardiograms demonstrated progressive enlargement of the intracardiac mass and left heart chambers. Due to recurrent pulmonary edema, development of atrial fibrillation, and poor quality of life, the owners elected euthanasia approximately 19 months after the initial diagnosis. A necropsy was performed. On gross observation, the lungs were slightly firm and mottled pink, light red, and pale brown. Pale yellow froth was present in the mainstem bronchi. A multinodular, firm, dark red mass, measuring 2.5 cm  2 cm, was adhered to the mitral valve. Several round, smooth, pale tan nodules measuring up to 1 cm in diameter were scattered along the endocardium of both ventricles. The peritoneal cavity contained 2.5 L of serous fluid. The liver was swollen, rounded, nodular, and light brown. On histopathology, sections of the valvular mass consisted of abundant fibrin surrounding a loosely cellular neoplasm composed of spindle cells forming streams, bundles, and palisades (Fig. 2),

151 supported by a fine to moderate, fibrous stroma. These cells were elongated, with moderate amounts of eosinophilic, fibrillar cytoplasm, and oval to polygonal nuclei, with finely to coarsely stippled chromatin, and inapparent nucleoli. Anisocytosis and anisokaryosis were moderate. No mitotic figures were noted. Multiple foci of hemorrhage, necrosis, fibrin, and infiltrates of lymphocytes and hemosiderin-laden macrophages were scattered throughout the neoplasm. In some areas of the mass, the spindle cells were noted to exhibit nuclear palisading with adjacent fibrillar, eosinophilic material (Verocay-like bodies, Antoni A pattern). A section through one of the nodular endocardial masses consisted of a more monomorphic population of these neoplastic cells and large numbers of infiltrating degenerate neutrophils. The mass was adhered to the endocardium via granulation tissue and fibrosis that was infiltrated by moderate numbers of lymphocytes and plasma cells. Immunohistochemistry of the valvular neoplasm for S-100 protein revealed faint to strong, cytoplasmic staining, consistent with a schwannoma (Fig. 3).

Discussion Cardiac tumors are relatively uncommon in dogs.1,2 In one study, the incidence of cardiac tumors was 0.19%.1 The most common cardiac tumors reported are hemangiosarcoma, aortic body tumors, lymphoma, and ectopic thyroid carcinoma.1,2 Other tumors rarely reported are myxoma, myxosarcoma, mesothelioma, fibroma, fibrosarcoma, rhabdomyoma, rhabdomyosarcoma, leiomyoma, and malignant peripheral nerve sheath tumor. Although an intracardiac malignant peripheral nerve sheath tumor has been described in the dog, to the authors’ knowledge, this is the first case of multiple benign intracardiac schwannomas.3 Neurogenic cardiac tumors are extremely rare and are almost always primary and benign, although malignant and metastatic neurogenic tumors have been reported.4e13,16 Schwannoma, also called peripheral nerve sheath tumor or neurofibroma, is most common in people 20e50 years of age.11e13 It frequently arises from the nervous system of the heart, primarily on the right side, especially from the right atrium.3,4,11,12,16 The reason postulated for this location is that the origins of cardiac schwannomas are from cardiac

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Figure 3 Immunohistochemistry of the valvular neoplasm for S-100 protein (400). Faint to strong cytoplasmic staining is present, consistent with schwannoma.

branches of the vagus nerve and cardiac plexus.4,11,16 Schwannomas can occasionally be found in the left atrium or near the left ventricle.12,13,16 The presence of multiple intracardiac schwannomas in this case is unusual. It is possible that these could represent metastases; however, malignancy was not supported by cell morphology or invasion, and a primary mass was not noted elsewhere in the patient. The clinical signs of cardiac schwannoma are related to their location. When located on the right atrium or in the pericardial sac, external compression of structures and pericardial effusion may occur.16 In people, this often results in the symptoms of chest pain, dyspnea, or syncope.14,15 When located inside the cardiac chambers, as in our case, valvular obstruction or regurgitation may lead to clinical signs of congestive heart failure.16 Echocardiography is a useful tool for the diagnosis of cardiac tumors including cardiac schwannoma.4,16 Magnetic resonance imaging and computed tomography are sometimes used in people for more detailed evaluation.4,16 In the case described here, we were able to define tumor size, shape, attachment, and mobility with transthoracic echocardiography; therefore, additional imaging modalities were not performed. Surgical excision, when possible, is considered the treatment of choice of cardiac schwannoma.4,11,12,15 If malignant schwannoma is present, partial resection, followed by radiation or chemotherapy, is a palliative option.4 In our case,

J.D. Thomason et al. inflow occlusion with mass resection was recommended; however, the owner elected conservative medical management. Histopathologic features of schwannoma include the biphasic architecture of Antoni A and B patterns, as well as nuclear palisading (Verocay bodies) and fibrous capsules containing the cells derived from the nerves.4,15,17 The Antoni A pattern contains elongated fascicles in the areas of moderate to high cellularity with a small stromal matrix.4,15,17 In the Antoni B pattern, the tumor is less densely cellular with a loose meshwork of cells along with microcysts and myxoid changes.4,15,17 A benign schwannoma was diagnosed in this case due to the presence of an Antoni A and B pattern, Verocay-like bodies, and S-100 immunopositivity, with only moderate cell pleomorphism, no evidence of invasion, and no mitotic activity. The fibrin and hemorrhage deposited primarily on the surface of the neoplasm is likely a reflection of turbulent blood flow and damage to the neoplasm. The inflammatory infiltrate was likely a response to this damage; however, bacteriology was not performed in this case due to the clear presence of a neoplasm. Secondary bacterial endocarditis is a possible consequence of abnormally structured and/or functioning valves. Immunohistochemistry is useful for confirmation of the diagnosis of schwannoma. The S-100 protein is used as a marker for schwannoma.4,15 It is obtained from the neural crest origin tumors from which the melanocytes and Schwann cells are derived.4,15 It can, however, stain non-specifically. In our case, S-100 immunopositivity, combined with cell morphology and arrangement supported a diagnosis of benign valvular and endocardial schwannoma.

Conflict of interest None.

Supplementary data Supplementary videos related to this article can be found online at http://dx.doi.org/10. 1016/j.jvc.2015.01.006.

Cardiac schwannoma in a dog

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Description

Transthoracic echocardiogram (right parasternal long axis view)

A pedunculated nodular mass involving the ventral aspect of the mural mitral valve leaflet and the endocardial surface of the left ventricular free wall is present. Severe left atrial and ventricular dilation is present. The pedunculated Transthoracic nodular mass is noted echocardiogram (right parasternal flailing between the left ventricular short axis view) papillary muscles. Zoom image of the Transthoracic mass involving the echocardiogram (right parasternal mural mitral valve leaflet and the long axis viewendocardial surface of zoom feature) the left ventricular free wall.

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4. Hwang SK, Jung SH. Schwannoma of the heart. Korean J Thorac Cardiovasc Surg 2014;47:141e144. 5. Miller AD, McDonough S. Interthalamic hematoma secondary to cerebrovascular atherosclerosis in an aged grizzly bear (ursus arctos horribilis) with primary cardiac schwannoma. J Zoo Wildl Med 2008;39:659e662. 6. Cho HS, Kim YS, Choi C, Lee JH, Masangkay JS, Park NY. Malignant schwannoma in an American buffalo (Bison bison bison). J Vet Med A Physiol Pathol Clin Med 2006;53: 432e434. 7. Johnson RC, Anderson WI, Luther PB, Ryan AM. Multicentric schwannoma in a mature Holstein cow. Vet Rec 1988;123: 649e650. 8. Teredesai A, Wohrmann T. Endocardial schwannoma in the Wister rat. J Vet Med A Physiol Pathol Clin Med 2005;52: 403e406. 9. Alison RH, Elwell MR, Jokinen MP, Dittrich KL, Boorman GA. Morphology and classification of 96 primary cardiac neoplasms in Fischer 344 rats. Vet Pathol 1987;24:488e494. 10. Robertson JL, Garman RH, Fowler EH. Spontaneous cardiac tumors in eight rats. Vet Pathol 1982;19:30e37. 11. Early SA, McGuinness J, Galvin J, Kennedy M, Hurley J. Asymptomatic schwannoma of the heart. J Cardiothorac Surg 2007;2:1e3. 12. Sirlak M, Uymaz OK, Tasoz R, Erden E, Ozyurda U, Akalin H. Primary benign schwannoma of the heart. Cardiovasc Pathol 2003;12:290e292. 13. Anderson CD, Hashimi S, Brown T, Moyers J, Farivar RS. Primary benign interatrial schwannoma encountered during aortic valve replacement. J Card Surg 2011;26:63e65. 14. Rajesh GN, Raju D, Haridasan V, Sajeev CG, Krishnan MN, Rajesh S, Kuriakose KM. Intrapericardial schwannoma presenting as acute coronary syndrome. J Am Coll Cardiol 2013; 62:e527. 15. Elstner K, Granger E, Wilson S, Kumaradevan N, Chew M, Harris C. Schwannoma of the pulmonary artery. Heart Lung Circ 2013;22:231e233. 16. Stolf NA, Santos GG, Sobral ML, Haddad VL. Primary schwannoma of the right atrium: successful surgical resection. Clinics (Sao Paulo) 2006;61:87e88. 17. Kurtkaya-Yapicier O, Scheithauer B, Woodruff JM. The pathobiologic spectrum of Schwannomas. Histol Histopathol 2003;18:925e934.

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Pulmonary edema secondary to a cardiac schwannoma in a dog.

A 4-year-old castrated labrador retriever presented for cardiac evaluation to determine the etiology of cardiogenic pulmonary edema diagnosed 1 month ...
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