title: Epithelial cyst of the cardiac papillary muscle: case report and review of the literature.
abstract: BACKGROUND
  Reports of endodermal heterotopia (previously known as inclusion cysts) in cardiac atria are rare and there is only a single previous case report of endodermal heterotopia in a cardiac papillary muscle.
  
  
  OBJECTIVE
  A cyst in a cardiac papillary muscle was identified during the autopsy of an 87-year-old man who had died from an unrelated myocardial infarction. The cyst was examined histologically and mucin staining and immunostaining were carried out.
  
  
  RESULTS
  We report a unilocular cyst in a cardiac papillary muscle, which is lined by low cuboidal, pseudostratified and occasionally ciliated respiratory-type epithelium, surrounded by a layer of smooth muscle. The immunohistochemical features (MNF116+, cytokeratin (CK)7+, CK8+, CK18+, CK19+, epithelial membrane antigen positive, scattered cells positive for neuroendocrine markers) suggest that this is an endodermal heterotopia. Immunostaining of positive thyroid transcription factor-1 provides evidence for bronchogenic differentiation.
  
  
  CONCLUSIONS
  The differential diagnoses of cystic structures in cardiac papillary muscle and the origin and importance of endodermal heterotopias are discussed.
authors.affiliation: Department of Histopathology, John Radcliffe Hospital, Oxford, UK. elizabeth.soilleux@orh.nhs.uk
authors.forename: E J
authors.initials: EJ
authors.lastname: Soilleux
authors.forename: D R
authors.initials: DR
authors.lastname: Davies
mesh_terms: D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D001994:Bronchogenic Cyst / Q000175:diagnosis / Q000473:pathology*; D009202:Cardiomyopathies / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000032:analysis; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D010210:Papillary Muscles / Q000473:pathology*; D014157:Transcription Factors
chemical_list: D015415:Biomarkers; D004268:DNA-Binding Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors