Heart
Cardiac tumors - benign
Rhabdomyoma

Author: Nat Pernick, M.D. (see Authors page)

Revised: 20 March 2018, last major update November 2013

Copyright: (c) 2007-2018, PathologyOutlines.com, Inc.

PubMed Search: Rhabdomyoma [title] heart pathology

Cite this page: Pernick, N. Rhabdomyoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/hearttumorrhabdomyoma.html. Accessed April 22nd, 2018.
Definition / general
  • 50 - 90% of primary heart tumors in children
  • Usually discovered in patients less than 1 year of age, rarely in fetuses (Ital Heart J 2002;3:48)
  • May obstruct valvular orifice or cardiac chamber; may present with sudden cardiac death (Pediatr Dev Pathol 2007;10:129)
  • Not a true neoplasm, but a hamartoma or malformation due to mutation in TSC1 and TSC2 genes
  • 50% of patients have tuberous sclerosis; sporadic cases are occasionally associated with congenital heart disease
Case reports
Treatment
  • Many tumors regress spontaneously
  • Excision if left ventricular outflow tract obstruction or refractory arrhythmia
Gross description
  • Small, firm, gray-white, well circumscribed myocardial masses (often multiple) that protrude into ventricles
  • Average size is 3 - 4 cm, up to 10 cm, particularly in sporadic cases
  • Rhabdomyomatosis: numerous miliary nodules less than 1 mm
Gross images

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Rhabdomyomatosis in patient
with tuberous sclerosis
and multiple minute tumors
studding epicardium
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Right ventricular mass



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Left ventricular tumor causing sudden death in children ages 1-2

Microscopic (histologic) description
  • Clear cells and large, rounded, polygonal cells ("spider cells") with glycogen vacuoles separated by strands of cytoplasm extending between cell membrane and nucleus
  • No mitotic activity
  • Adult tumors: more cellular with smaller cells, few spider cells and more cellular proliferation (Hum Pathol 2002;33:1092)
Microscopic (histologic) images

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Spider cell (center)
and intracellular
myofilaments
(oil emersion)
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Muscle specific actin
highlights spider
cells and cross
striations (arrowheads)


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Drawings from 1938 report

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Fig A: well circumscribed, tan-yellow masses in left atrium and left ventricle
Fig B: large cells with clear cytoplasm (spider cells)
Fig C: spider cells surrounded by normal myocytes

Positive stains
Negative stains
Electron microscopy description
  • Altered myocytes with abundant glycogen, small and sparse mitochondria
  • Cellular junctions resembling intercalated disks are extensive and randomly distributed, not just at poles of cell as in normal myocytes (Hum Pathol 1977;8:700)
Electron microscopy images

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Abundant glycogen, small and
sparse mitochondria, fragmented
irregular myofilaments with Z bands
Differential diagnosis
  • Glycogen storage disease: no well formed nodules, cells have intercalated disks at poles by EM
  • Granular cell tumor: epicardial, no vacuoles, no myofibers, S100+, desmin-, myoglobin-
  • Histiocytoid myopathy: small tumor nodules, finely granular cells, no large vacuoles, no spider cells; a variant of rhabdomyomatosis
  • Lipoma: usually epicardial, no myofibers, no glycogen
Additional references