Benign tumors
Blood cyst

Topic Completed: 1 November 2013

Minor changes: 26 September 2019

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

PubMed Search: Blood cyst [title] heart

Nat Pernick, M.D.
Page views in 2019: 333
Page views in 2020 to date: 104
Cite this page: Pernick N. Blood cyst. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/hearttumorbloodcyst.html. Accessed July 10th, 2020.
Definition / general
  • Congenital cyst found on endocardium, particularly along lines of closure of heart valves
  • More common on mitral and tricuspid valves
  • Actually diverticula (invagination of atrial endothelium into atrioventricular valves or ventricular endothelium into semilunar valves)
  • Incidental findings in 50% of infants under age 2 months on cardiac valves; rare after age 2 years
  • Rarely causes ventricular or valvular obstruction
Case reports
Gross description
  • Usually 3 mm or less
  • May be blue
  • 50% are multiple, may have up to 20 cysts
Gross images
Missing Image

4 mm cyst is incidental
finding on tricuspid valve
of 4 month old who died
of unrelated causes

Images hosted on other servers:
Missing Image

Seen with
Microscopic (histologic) description
  • Blood filled cystic cavity with fibromyxoid wall lined by flattened or cobblestone shaped endothelium
  • Filled with nonorganized blood
Microscopic (histologic) images

Images hosted on other servers:
Missing Image

Non-organized blood in a sac lined by endothelium

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