March 2022 – Cardiovascular Pathology

During the autopsy of a 72-year-old woman, the lesion shown below was identified in the right atrium in the vicinity of the fossa ovalis. Grossly, the lesion was dark red, soft, and slightly raised from the endocardium.

Figure 1
Figure 2
Figure 3
Figure 4

Based on the histology below, what is your diagnosis?

  • Atrial thrombus
  • Cardiac hemangioma
  • Cardiac myxoma
  • Intracardiac varix

The correct answer is ...

Intracardiac varix.

This lesion is an example of an intracardiac varix. This is a rare, benign lesion which predominately affects the right atrium. Only few case reports of this entity in living individuals have been published and it can be challenging to diagnose by cardiac imaging. While still rare, intracardiac varices are more readily observed incidentally during autopsy cases such as this case. Intracardiac varix are hypothesized to arise from the dilated veins of the endocardium. Grossly they appear as endocardial-based red or venous blood-colored smooth masses. Histologically, they classically show a cystic structure with an endothelial lining. Diagnosis relies on the identification of a vessel wall associated with the cysts. An elastic marker, such as Verhoeff's stain, can be used to visual the vessel elastin. The cysts are frequently associated with a luminal thrombus and calcification. The majority of the reported intracardiac varix have been incidental findings; however, few reports of large varix have been hypothesized to be the source of cardiac emboli. 

Cardiac hemangioma are vascular neoplasms which can affect the pericardium or endocardium, also, predominately found in the right atrium. The most common subtype, cavernous, demonstrates numerous large, dilated vessels with a surrounding myxoid background. The vascular spaces typically show pools of blood within the vessels. Calcification can occur in hemangiomas but is not a hallmark feature as seen in an intracardiac varix.  

Differentiating an intracardiac varix from a thrombus can be challenging. Thrombi do not originate subendocardially, therefore histologically differentiating if the lesion is involving a vessel or a vessel lumen is key for the diagnosis. Cardiac myxomas are one of the most common cardiac neoplasms. Histologically they typically show elongated tumor cells with ovoid nuclei and amphophilic cytoplasm in a myxoid background. Although myxomas are most common in the left atrium, they also occur in the right atrium. Interestingly, bilateral myxomas have been reported in patients with Carney complex, a rare genetic neoplastic syndrome.  

Carney complex patients are at an increased risk of developing myxomas in addition to several other skin lesions and endocrine tumors. Myxomas typically are not associated with calcifications or cystic features. Myxomas predominately exhibit a benign behavior (with rare malignant variants), however they can be the source of systemic embolization.   


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  3. Okamoto, N., et al., Long-term follow-up of a rare calcified cardiac tumor: a case report. J Echocardiogr, 2012. 10(3): p. 95-7.
  4. Rajani, R., N. Sarangmath, and B. Mishra, Massive right atrial myxoma. Int J Cardiol, 2008. 128(1): p. 121-2.
  5. Thorsen, M.K., et al., Mobile intracardiac varix: a new echocardiographic entity. AJR Am J Roentgenol, 1982. 138(3): p. 574-6.
  6. WHO Classification of Tumours Editorial Board. Thoracic tumours. Lyon (France): International Agency for Research on Cancer; 2021. (WHO classification of tumours series, 5th ed.; vol. 5).

Blake Ebner, M.D., Ph.D.

Resident, Anatomic Pathology/ Neuropathology
Mayo Clinic

Marie Christine Aubry, M.D.

Consultant, Anatomic Pathology
Mayo Clinic
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

MCL Education

This post was developed by our Education and Technical Publications Team.