SPR Unknown # 81-- FINAL

Kim Dannull, M.D.


Publication Date: 2013-01-04

History

Abnormal prenatal imaging

Findings

Fetal MRI demonstrates a large cardiac tumor (here rhabdomyoma) of the left ventricular free wall with narrowing of the left ventricle lumen. (Multiple additional cardiac rhabdomyomas were present in this fetus, which are not shown). Single axial T2 weighted image of the brain demonstrate multiple subependymal nodules lining the right ventricle and coronal T1 weighted images of the fetus and brain demonstrate multiple cortical/subcortical regions of increased signal, compatible with cortical/subcortical tubers. Multiple renal cysts are present bilaterally.

Diagnosis

Tuberous Sclerosis with mutation of both the TSC2 and PKD1 gene.

Differential Diagnosis

Teratoma – usually extracardiac (pericardial > mediastinal) with an attachment to the aortic root or pulmonary artery. Heterogeneous with calcifications. Pericardial effusion frequently associated.

Fibroma – usually solitary and originate from LV apex. Most are homogeneous, but they can have cystic degeneration and calcifications. Can be quite large. May have pleural effusion.

– Vascular tumors (hemangiomas) – rare and usually located at the base of the heart adjacent to the atria. Can also have cysts and calcifications.

Myxoma - Not typically seen in utero. Usually from the interatrial septum at fossa ovalis with extension into the left atria (85%) more common than the right. Homogeneous and of moderate echogenicity. Isointense on T1 and hyperintense on T2.

– Echogenic cardiac focussmall, < 3 mm focus which is very echogenic (bright as bone). Associated with papillary muscle. Usually incidental, but soft marker for trisomy 21.

Moderator band – Distinguishing feature that identifies the right ventricle. Normal muscle band from free wall to septum, usually makes 45 degree angle from the apex.

Papillary musclenormal feature of right and left ventricles.

– Metastatic cardiac lesion – Rare, particularly in a fetus.

Discussion

• Of all fetal cardiac tumors, approximately 60-80% are rhabdomyoma.

• If a single rhabodomyoma is present, 60-95% are associated with tuberous sclerosis. If there are multiple cardiac rhabodmyomas, the diagnosis is almost certainly tuberous sclerosis.

• Cardiac rhabdomyomas have not been reported in a fetus prior to 20 weeks of gestation.

Maximum growth of cardiac rhabdomyomas is between 22 to 32 weeks. These cardiac tumors rarely grow after 35 weeks and all either stop growing or regress postnatally.

• 2/3 of tuberous sclerosis are from a new mutation.

• 1/3 of cases have an affected parent with a single gene mutation of either TSC1 or TSC2. TS is inherited as an autosomal dominant disorder with variable penetrance.

• Of the cases of tuberous sclerosis, 70% are caused by a mutation in the TSC2 gene (tuberin) which is located on chromosome 19. This gene is in very close proximity to the PKD1 gene which may be affected as well. Therefore, renal cysts are often a prominent feature of TSC2 mutation, however are not usually seen until 7-10 years of age. The number of cysts present in this fetus is unusual. The remaining 30% of TS cases are caused by a mutation in the TSC 1 gene (hamartin) which is located on chromosome 9.

• In general, a mutation in TSC2 is more severe than a mutation in the TSC1 gene.

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