Abstract
Myxomas, metastatic tumors, thrombi and vegetations top the differential diagnosis list of cardiac masses. We present a case of ectopic liver tissue, a far less common etiology of right atrial mass discovered incidentally on transthoracic echocardiography (TTE) of a 37-year-old female with multiple comorbidities who was referred to our facility for further management of left popliteal artery occlusion and right lower extremity cellulitis. We discuss further the categories, pathogenesis, diagnostic approach and potential complications of ectopic liver tissue.
Introduction
Aberrant liver tissue is an exceedingly rare condition that may have clinical implications ranging from mechanical compression to malignant transformation [1]. Typically, the aberrant hepatic tissue is found in abdominal organs, however, it has been described in the thoracic cavity [2]. In extremely rare occasions, ectopic hepatic tissue can present as right atrial mass. Fujimoto and colleagues [3]. described the first case of intracardiac aberrant liver tissue mistakenly diagnosed as a right atrial tumor.
Case presentation
A 37-year-old Caucasian female with past medical history significant for spina bifida complicated by paraplegia and neurogenic bladder, kyphoscoliosis with multiple spine surgeries, hypertension, sinus tachycardia, depression and multiple episodes of right lower leg cellulitis presented as a transfer to our tertiary medical center for further management of left popliteal artery occlusion and right lower extremity cellulitis. Her daily medications were trazodone, celexa, tolterodine, propranolol, wellbutrin and hydrochlorothiazide.
On physical examination, she was calm, cooperative and in no acute distress. She weighed 65 kg and was 134 cm tall. Her blood pressure was 119/85 mm Hg, heart rate 101per minute, temperature 98.8°F, respiratory rate 18 per minute and arterial oxygen saturation was 96% on 2 liters nasal canula. Head and neck examination were normal, moist oral mucosa with no oral thrush or ulcers noted. There were no abnormal lung or heart sounds. Abdomen was soft, non-distended, non-tender, with no rebound or guarding and normal bowel sounds. kyphoscoliosis of the back, underdeveloped paraplegic lower extremities with bilateral sensory loss, intact distal pulses in left foot with warm pink toes. Right lower leg and foot were swollen, erythematous, non-tender with bullae of serosanguinous fluid. Her laboratory tests were normal except for hypokalemia with potassium 2.4 mmol/L, lactic acid of 1.6 mmol/L.
Vascular surgery team was consulted, she was started on heparin drip for left popliteal artery thromboembolism and recommendation was made for TTE and antiphospholipid syndrome screening.
TTE showed cardiac mass in right atrium extending into inferior vena cava (IVC). For further identification of the mass, cardiac MRI was done that showed normal left ventricular ejection fraction of 57%, right ventricular dilatation with moderately reduced systolic function of 36% and mass like structure projecting over the right atrium with appearance most suspicious for diaphragmatic caval foramen herniation of liver parenchyma encroaching on right atrium. Sulphur colloid nuclear single-photon emission computed tomography (SPECT) study also confirmed this finding. She continued inpatient treatment with anticoagulation and antibiotics during which she was seen by cardiology who recommended outpatient follow-up with cardiothoracic surgery for evaluation for potential surgical excision of the right atrial mass that was found to be herniated liver tissue.
Discussion
The vast majority of intracardiac tumors are secondary to metastatic disease. Primary cardiac tumors are extremely rare and 75% of the time are benign. Myxoma is the most common primary cardiac tumor [4].
Intracardiac mass differential diagnosis is broad. It includes tumor, thrombus, vegetation or foreign body. It also can be an extremely rare presentation of heterotopic liver that herniated through vena cava into right atrium which can be mistakenly diagnosed as right atrial tumor [3].
Ectopic liver is a rare condition that can be classified into 4 categories: (i) an accessory liver lobe attached to the liver, (ii) a large accessory liver lobe with a connecting stalk to the liver, (iii) ectopic liver without connection to the liver, and (iv) microscopic ectopic liver tissue [4]. The present case is consistent with the second type of ectopic liver tissue. Typically, presentation of aberrant hepatic tissue is in abdominal cavity, however, it has been reported in the thoracic cavity [5]. Few cases in which ectopic liver parenchyma has been described as a right atrial mass [6, 7, 8].
In the absence of trauma, the pathogenesis of heterotopic liver tissue is still unclear. Controversial theories have been documented in effort to explain this liver tissue aberrancy. One theory proposed that it is a congenital defect of the septum transversum, embryonic tissue that differentiates into both the diaphragm and ventral mesentery of the foregut [1]. However, authors of another case report hypothesized that there can be hematogenous migration of hepatic cells with regenerative capacity even after intrauterine development. They supported their hypothesis with absence of detectable right atrial mass on TTE performed 18 months prior to her presentation [9].
Although this ectopic liver tissue was discovered as incidental finding during TTE. It can have serious clinical implications. Chapman-Fredrick et al. described a case of inferior vena cava (IVC) obstruction by hernia liver mass. That can lead to downstream venous congestion and higher risk of thromboembolic complications [10]. Another clinical implication is malignant transformation of aberrant liver tissue. Matsuyama M et al. Reviewed 100 cases of aberrant hepatic tissue and reported that 28 patients were found to have hepatocellular carcinoma on pathologic review of the tissue [11]. This potential risk of carcinogenesis should increase the urgency for closer follow up and surgical excision with negative margins, and careful pathologic review of the ectopic tissue.
Most cardiac masses are found incidentally during routine cardiac imaging. TTE is the most commonly used, due to its low cost, portability, widespread availability, lack of ionizing radiation, and ability to evaluate both anatomy and function of the heart. However, there are pitfalls to TTE. It may not be able to differentiate herniated liver masses from an atrial myxoma, secondary malignant masses and in some cases thrombus or vegetations. These limitations are resulting from poor acoustic window, being operator dependent and narrower field of view [12]. Cardiac magnetic resonance imaging (MRI) might be of more value as it offers several advantages over TTE, such as a large unrestricted field of view, superior soft-tissue contrast, operator independence, and consistent reproducibility [13]. Thus, cardiac MRI is a very helpful diagnostic tool when an intracardiac mass cannot be characterized by TTE.
Conclusion
In exceedingly rare occasions, heterotopic hepatic tissue can present as right atrial mass that can be mistakenly diagnosed as right atrial myxoma or other more common etiologies of cardiac mass. Cardiac MRI should be the next step when TTE study is not able to clearly characterize the right atrial mass. As this ectopic liver tissue carries a risk of malignant transformation, close monitoring and surgical excision with safety margins should be considered.