Synonyms: Fibrous hamartoma, fibroelastic hamartoma and nodular fibroelastosis.

Prevalence: Any cardiac tumors, all ages: 1-2:10,000¹, infants only: 0.17-28:10,000^2,3, fibromas represent 12-25% of these^1,3,4,5.

Definition: Considered a subset of the soft tissue fibromatoses, fibromas of the heart are benign connective tissue tumors derived from fibroblasts. They are usually single, sharply demarcated, occurring in the free wall of the left ventricle or in the intraventricular septum.

Etiology: Unknown.

Pathogenesis: Unclear, non-neoplastic proliferation of fibrous tissue (as evidenced by lack of distinct capsule, presence of myocardial fibers within the proliferation) versus true neoplasm of fibroblastic origin.

Associated anomalies: Orofacial clefts³, cystic renal dysplasia²⁷.

Resulting anomalies: Arrhythmias, hypoplasia of chambers and great vessels, hydrops, pericardial effusion, emboli^2,6,7.

Differential diagnosis:  Any other cardiac tumor, including rhabdomyoma, teratoma, myxoma, sarcoma (see Table 1).

Prognosis: Dependent upon associated cardiac anomalies and conduction disturbances. Often fatal, with hypoplastic left or right heart.

Recurrence risk: Not known to be increased.

Management: Dependent upon associated cardiac anomalies and resectability of tumor. Cases of both partial and complete resection with long-term satisfactory results have been described ^8-12.

MESH Heart-Neoplasms-congenital, complications, diagnosis, pathology; Fibroma-diagnosis, complications, congenital, pathology. ICD9 212.7 CDC 746.990

* Address correspondence to Timothy W. Malish, MD Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 21^st and Garland Ave, Nashville, TN 37232-2675. Ph 615-322-0999 Fax 615-322-3764

Introduction

Cardiac tumors are rare, and the most commonly reported tumors are rhabdomyoma. We wish to report the appearance of a fibroma. To our knowledge, this is the first in utero detection of a primary cardiac tumor proven to be fibroma. In addition, this case reports the earliest in utero documentation of an intracardiac tumor by ultrasound.

Case report

A 31-year-old G₂ P₁₀₀₁ patient presented at 14 weeks of gestation with vaginal bleeding and spotting. The ultrasound examination revealed a partial placenta previa with no other  abnormalities. The patient"s medical history was unremarkable except for mitral valve prolapse and an uncomplicated spontaneous vaginal delivery of a 3,000g girl 29 months before the current pregnancy.

A follow-up ultrasonogram performed at 20 weeks of gestation showed an echogenic mass arising from the interventricular septum and the free wall of the left ventricle (fig. 1-2).

Fig. 3: The ascending aorta is hypoplastic and the main pulmonary artery enlarged.

Fig. 4: Color Doppler demonstrates a paucity of flow in the left ventricle.

The left ventricle and the ascending aorta were hypoplastic (fig. 2-4). The diagnosis of cardiac tumor was made. The patient underwent a prostaglandin induction and delivered a non-viable 495g male infant.

The autopsy confirmed that only the heart was abnormal.  The heart weighed 2.8 grams (normal 4.6g). The aorta was hypoplastic. Sectioning through the heart revealed a mass that arose from the septum and the free wall of the left ventricle and encroached upon the left ventricle.

The mass was somewhat off-white with some dark brown color within it which was suggestive of hemorrhage (fig. 5).

Fig. 5: Bivalve section of the heart. Whitish tissue invades the interventricular septum (white arrows) and the free wall of the left ventricle (black arrows).

Histologic section of the mass revealed numerous fibroblasts as well as dystrophic calcification, consistent with a fibroma.

Discussion

Prevalence

Primary cardiac tumors in infants are rare, with estimates of incidence ranging from 0.17-28:10,000³.  Ninety percent of these tumors are benign¹³. Rhabdomyomas are the most common of the primary neoplasms (40-60%), followed by teratoma (19-25%) and then fibroma (12-25%)^1,3-5,13-15.

Location

A fibroma frequently arises from the interventricular septum or the free wall of the ventricles^1,3; it is uncommon in the atria. It may invade the conducting system⁴, resulting in arrhythmias.

Ultrasound appearance

In our case, the fibroma appeared as a very echogenic mass without acoustic shadowing. This mass was more discrete than that of rhabdomyoma, which are often more bulky.

Etiology

The etiology is unknown and familial incidence has not been described.

Pathogenesis

There is some debate as to the pathogenesis of the cardiac fibroma. Some investigators believe it to represent non-neoplastic proliferation of fibrous tissue. They point to the lack of a distinct capsule and presence of myocardial fibers within the proliferation as evidence for this view. Others believe this to represent a true neoplasm of fibroblastic origin.

Associated anomalies

Congenital cardiac tumors can be associated with severe obstruction of blood flow, hypoplasia of the cardiac chambers or great vessels, atresias of the cardiac valves, disturbances of the conduction system, nonimmunologic hydrops fetalis, pericardial effusion and embolic phenomena. Fibroma has  been associated with orofacial cleft in one case³ and cystic renal dysplasia in another²⁷ .

Differential diagnosis

The differential diagnosis of a cardiac tumor includes rhabdomyoma, myxoma, teratoma and hemangioma. Their main characteristics are described in Table 1.

Prognosis

Although pathologically benign, cardiac fibroma cause death by obstruction of blood flow, arrhythmia, pericardial effusion or embolic phenomena. Obstruction of the flow, may result in hypoplasia of the chamber and vessel that is obstructed. The outcome of the fetus thus become functionally equivalent to that of a fetus with a hypoplastic right or left heart, and the prognosis for hypoplastic right or left heart can be used in counseling the parents.

Management

When the diagnosis of a cardiac tumor is made before viability, the option of pregnancy termination should be offered. Serial ultrasound examinations should be performed to search for signs of congestive heart failure. The development of hydrops associated with a structural cardiac defect is an ominous finding. The optimal management of these patients has not been established. In the absence of severe structural anomaly or congestive heart failure, there is no need to modify standard obstetrical management, but delivery in a tertiary care center where a pediatric cardiologist is immediately available is mandatory.

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