Cardiac tumors - benign
Lipomatous hypertrophy of cardiac intraatrial septum

Topic Completed: 1 November 2013

Revised: 26 September 2019

Copyright: 2007-2019, PathologyOutlines.com, Inc.

PubMed Search: Lipomatous hypertrophy of cardiac intra atrial septum

Nat Pernick, M.D.
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Cite this page: Pernick N. Lipomatous hypertrophy of cardiac intraatrial septum. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/hearttumorlipomatoushypertrophy.html. Accessed December 8th, 2019.
Definition / general
  • Rare (0.6% of cardiac tumors); usually age 60+ years
  • Associated with increased epicardial fat (heart floats in water), mild to severe obesity
  • Symptoms include congestive heart failure, atrial fibrillation, supraventricular tachycardia, syncope, sudden unexpected cardiac death (Arch Pathol Lab Med 2006;130:397)
  • Often diagnosed at autopsy (Cesk Patol 2006;42:182)
  • "Hypertrophy" is a misnomer because mass is due to increased fat cells, not hypertrophied myocytes
Gross description
  • Unencapsulated mass usually confined to atrium
  • Resembles brown fat
  • Associated with cardiac hypertrophy
  • Septal thickness is 2 to 7 cm (normal is < 1 cm)
  • Fossa ovalis is usually spared
Gross images
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Fatty deposit superior to fossa ovalis

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Huge fatty tumor of atrial septum sparing fossa ovalis

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Tumor adjacent to epicardial fat

Microscopic (histologic) description
  • Multivacuolated fatty infiltration more than 2 cm thick in atrial septum
  • Cells have central nuclei without atypia
  • Some fat cells resemble brown fat and fat cells in malnourished patients
  • Usually atypical and hypertrophied myocytes (Am J Surg Pathol 1996;20:678)
  • Variable bands of collagen and chronic inflammatory infiltrates
  • No mitotic figures, no signet ring structures, no enlarged hyperchromatic and indented nuclei in fat cells
Microscopic (histologic) images
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Mixture of normal fat, vesicular fat and hypertrophied myocytes

Images hosted on other servers:
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Mixture of normal
fat, vesicular fat
and hypertrophied
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Gross and micro images

Electron microscopy description
  • Abundant mitochondria in vesicular fat cells
Differential diagnosis
  • Lipoma: encapsulated, no muscle fibers
  • Liposarcoma: lipoblasts have large clear vacuoles and hyperchromatic indented nuclei
  • Myxoma: has stellate or globular cells, myxoid areas, no fat, no hypertrophied myocytes
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