I half-remember some mainstream media article about a peculiar growth/tumor in which the vascular tissue itself had started to beat/pulse as if it were a sort of heart.

I cannot remember any other significant details about it, especially not whether this was unique or if more than one instance had been documented.

I am aware of teratomas and how they can develop into all sorts of different tissue (sometimes even multiple tissues in a single occurrence), but I had thought that these relegated themselves to other tissues more boring than cardiac tissue.

Am I misremembering this, or (more likely still) had science/medical reporting just conflated something, or have any such occurrences ever been documented?

I am curious for any details, though ideally someone can provide something closer to actual medical reports.

  • Seems perfectly plausible, teratomas can be pretty complex - any reason for the interest?
    – Bryan Krause
    Sep 14, 2020 at 20:41
  • @BryanKrause Concept for a novel. Trying to do research, but can't even begin to think of how to start a search on it. Not a big reader of medical journals, but would welcome citations to those.
    – John O
    Sep 14, 2020 at 20:43
  • 1
    Datapoint just maybe: A few months ago I had a PVI procedure to stop recurring bouts of Atrial fibrillation. These are triggered (I'm told) by spurious signals originating in the Pulmonary veins. Treatment is (in my case) cryogenic freezing to produce scar tissue "rings" around the vein entries to isolate the triggering signals. [On a "good event" I'd get bradycardia at maybe 30 bpm for a while, then suddenly tachycardia at around 200 bpm and then after a minute or two Atrial fibrillation. Here we go again ... . Sep 15, 2020 at 9:22

1 Answer 1


The term you're looking for is pericardial teratoma. Another related term you'll be interested in is fetus-in-fetu, which is essentially a parasitic twin growing somewhere within the body, usually the abdominal cavity.

There have been at least two examples of pericardial teratomas that developed sufficiently to produce heart-like pumping activity. The following case history is from 2002, so it's possible more examples exist now, but you'll see that it describes exactly what you remember reading about. The authors conclude it may be an example of an intermediate combination of fetus-in-fetu and teratoma.

Case Report:

A mature teratoma was identified in a two-month-old girl who was operated for a sacrococcygeal mass. The cystic components of the mass were accidentally opened during surgery, and a solid, rudimentary organ resembling a heart emerged. It had a vascular pedicle and a pulsation like cardiac activity different from the infant's heart rate. The mass was totally excised together with the coccyx, and in histological examinations, it was diagnosed as a mature teratoma and a rudimentary heart. To the best of our knowledge, the case presented in this report is only the second case of a cardiac development in a teratoma in the literature. In the light of data obtained about this case and related literature, we consider that fetus-in-fetu and teratoma may not be irrelevant entities, and that they possibly have the same developmental malformation. We also suggest that such an intermediate case is a combination of fetus-in-fetu and teratoma.

  • 4
    I wonder how much "accidentally opened during surgery" correlates with "operating surgeon's curiosity". Surprised this is only the second case reported at that time, nice find.
    – Bryan Krause
    Sep 14, 2020 at 22:05
  • @BryanKrause Yeah, that was my first thought too. That surgeon just had to see for themself what was in there.
    – Carey Gregory
    Sep 14, 2020 at 22:23

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