June 2016

A 26 year old male with incidental cardiac mass

Nariman A. Nawar, M.D.; Trevor Wolfe, PA; H. James Williams, M.D.

Overview

A 26 year old male patient with no significant past medical or surgical history was undergoing routine evaluation as a potential kidney donor for a relative. On routine systemic review the patient reported occasional shortness of breath.  A chest CT scan revealed an unexpected mass in the left atrium. Transesophageal echocardiography, showed the mass to be attached to the interatrial septum and prolapsed into the mitral valve causing significant stenosis. A decision was made for surgical intervention to remove the atrial mass. Intraoperatively the attachment of the mass to the interatrial septum was identified and the mass was entirely resected. The resection resulted in a septal defect which was then closed with a pericardial patch. The patient tolerated the procedure well and had no postoperative complications.

Gross and Microscopic Descriptions

Gross

The resected specimen consisted of a 3.3 x 3.2 x 2.0 cm tan-brown nodular mass with focal yellow discoloration and a stalk measuring up to 1.0 cm (Figure 1). The mass was serially sectioned to reveal gelatinous, homogeneous cut surfaces without calcification or necrosis. Representative sections were submitted for microscopic examination.

fig1a.jpg
fig1b.jpg
Figure1: Gross appearance of the mass. A) Shows the lobulated appearance of the mass surface. B) The mass cut surface is shown with an apparent 1.0 cm stalk (arrow).

Microscopic

The lesion was moderately cellular with spindly cells floating in a myxoid background in short cords and scattered individual cells. The cells had cytoplasmic processes, and some were ovoid with eosinophilic cytoplasm. The nuclei were small and the nuclear to cytoplasmic ratio was preserved (Figure 2). No areas of atypical mitosis or necrosis were seen.

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fig2b.jpg
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Figure 2: Microscopic sections from the mass. A) Low power shows moderately cellular tissue with myxoid background; the arrow indicates the stalk. B) Medium power shows myxoid background and cells in short cords as well as scattered individual cells. C) High power shows cells with cytoplasmic processes (marked by asterisk) and bland nuclear features. No mitoses are seen.

Diagnosis

Which of the following is the most likely diagnosis ?

Answer

Please select an answer above.

Discussion

Cardiac myxoma is a benign cardiac tumor that constitutes 75% of primary cardiac tumors. It arises from the left atrial wall in 80% of cases. Cases arising from the right atrium and from the ventricular walls have also been described. Approximately 90% of cases are sporadic and 5-10% are familial with associated with Carney complex. Clinically, cardiac myxoma can be asymptomatic and discovered incidentally in chest radiographs. Symptomatic cardiac myxomas usually present in children and young adults with signs and symptoms of mitral valve stenosis (i.e. shortness of breath, fatigue, and abnormal heart sounds).  Rarely, cardiac myxoma presents initially with intra-cerebral embolization, bacteremia secondary to myxoma infection, or is discovered during autopsy in cases of sudden cardiac death. [1-3,6]

The cell of origin and the pathogenesis of cardiac myxoma has not yet been established. Researchers hypothesize that cardiac myxoma arises from stem cells. The pathogenesis might be linked to a frameshift mutation involving the PRKAR1A gene, which is the defining mutation for Carney complex. This concept could explain the pathogenesis of familial cardiac myxomas associated with Carney complex but does not explain sporadic cases. [4-5]

On gross examination, cardiac myxoma tend be gelatinous, myxoid, and friable, but may have focal fibrosis. The gelatinous consistency of cardiac myxoma is secondary to mucopolysaccharide deposition. In 17% of cases, cardiac elastic fibers in myxomas can degenerate and result in the formation of calcific nodules, known as Gamna bodies. Microscopically, cardiac myxoma consists of bland cells in a myxoid background. Cells can be scattered single cells or be arranged in cords or ducts. The cells can be ovoid, spindly, or stellate in shape. Cytological atypia, mitotic activity, and necrosis are not expected to be seen in cardiac myxoma.

Myxoma cells stain positive for vimentin and calretinin. Occasionally, myxoma cells express CD117, thrombomodulin, cytokeratin and S-100. Because of this non-specific pattern of staining, the pathologist should not depend solely on immunophenotypic features to diagnose cardiac myxoma. [1, 4]

The differential diagnosis of cardiac myxoma includes: cardiac fibroma, papillary fibroelastoma, inflammatory myofibroblastic tumor, organizing thrombus, and hemangioma. The clinical and the morphological characteristics of cardiac myxoma mimickers are summarized in table 1. 

Treatment of cardiac myxoma is surgical excision. The prognosis is generally good with a local recurrence rate of 2%. Recurrences can occur in familial cases in association with Carney complex, in sporadic cases due to incomplete surgical resection, or due to tumor multifocality. Complications such as infection, emboli to the central nervous system or other sites, and sudden cardiac death have been reported. [1,6]

Back to our case:
The presentation in our case was incidental. Although the transesophageal echocardiography showed significant mitral valve obstruction, the patient reported no symptoms of mitral valve insufficiency or cardiac strain except for the occasional shortness of breath. The microscopic features were classical for cardiac myxoma and no ancillary studies were performed.

Cardiac myxoma mimickers

Mimicker: Papillary fibroelastoma

Clinical features:

  • Most are asymptomatic.
  • When symptomatic it presents with angina and transient ischemic attacks.

Pathology Gross (G): Papillary mass, looks like (sea anemones).
Pathology Microscopic (M): Avascular papillary fronds lined by bland endothelial cells.

Mimicker: Fibroma

Clinical features:

  • Presents in children and can be part of Gorlin syndrome.
  • Symptoms include: Congestive heart failure, arrhythmia and sudden death.

Pathology Gross (G): Rubbery, white mass with whorled cut surfaces.
Pathology Microscopic (M): Moderately cellular mass consisting of bland fibroblasts and collagen fibers.

Mimicker: Inflammatory myofibroblastic tumor

Clinical features:

  • Presents in any age, but more common in children.
  • Symptoms include fever, malaise, and weight loss.

Pathology Gross (G): Multinodular mass with focal calcification.
Pathology Microscopic (M): Bland spindle cells and inflammatory cells.

Mimicker: Hemangioma

Clinical features:

  • Rare and most cases are described in children as an incidental findings.

Pathology Microscopic (M):

  • Can be of capillary type or cavernous type.
  • The capillary type consists of small blood vessels, while the cavernous type has large dilated vascular channels.
  • Cardiac hemangioma can have myxoid degeneration, which makes the distinction from cardiac myxoma challenging.

References

  1. Virmani R, Farb A, Burke A. Benign cardiac tumor. Atlas of cardiovascular pathology. United States of America: 1996. P. 81-92.
  2. Patel J, Patel S, Sheppard MN. Benign cardiac tumours associated with sudden death. Europace. 2014 Jun;16(6):855-60.
  3. Sha D, Fan G, Zhang J. Multiple cerebral infarction as the initial manifestation of left atrial myxoma: A case report and literature review. Acta Cardiol. 2014 Apr;69(2):189-92.
  4. Di Vito A1, Mignogna C, Donato G, The mysterious pathways of cardiac myxomas: A review of histogenesis, pathogenesis and pathology. Histopathology, 2015 Feb;66(3):321-32.
  5. Singhal P, Luk A, Rao V, Butany J. Molecular Basis of Cardiac Myxomas. Int J Mol Sci. 2014 Jan 20;15(1):1315-37.
  6. Sardar MR, Lahoti A, Khaji A1, Saeed W, Maqsood K, Zegel HG, Romanelli JE, McGeehin FC 3rd. Recurrent right ventricular cardiac myxoma in a patient with Carney complex: A case report. J Med Case Rep. 2014 May 2;8:134. doi: 10.1186/1752-1947-8-134.