That is not possible.

What presumably happened is that there was an undetected early cancer. That left circulating tumor cells throughout a body otherwise filled with healthy tissues. Unless you find those specific cells, there will be no sign of a problem. (At least not until they find a home and start a new cancer.)

See https://en.wikipedia.org/wiki/Circulating_tumor_cell for more.

I'm surprised about this.

I get that there can be circulating cells, but the probability of them successfully metastasising in the early stages is very low.

Normally it's only later stage cancers that end up spreading.

I guess it's down to the immunosuppression making metastasis more viable.

I'm not an expert, but my understanding is that the probability or rate (or expected time) of metastasizing varies a lot depending on the type of the tumor. (I looked into this a bit when I was diagnosed; it was more or less likely to metastasize within a somewhat short time, depending on the exact type of the tumor.)

I'm sure the immunosuppressants needed after a transplant would increase the risk in any case.

If it wasn't a surprising situation, it wouldn't have been in a medical journal.

However its possibility isn't crazy. Per https://www.ncbi.nlm.nih.gov/pmc/articles/PMC22534/ it seems that cancer cells can be detected in the blood before the cancer itself is detectable by traditional means. Therefore an undiscovered cancer could well have left circulating cells in multiple organs.

> The diagnosis of breast cancer was occult at the time of donation.

I.e. they didn't find evidence of it at the time of donation.

So would it be valid to say that all transplant recipients have a significantly higher risk of developing cancer ?

Yes, but it's largely because of the lifelong immunosuppression to not reject the transplant reducing the body's ability to combat cancer. Of course, it's still better than not having that organ!

https://www.cancer.gov/about-cancer/causes-prevention/risk/i...

In addition, different organs need different amounts of immunosuppression. Livers are used to filtering random things and thus the body is more tolerant of livers (needs less immunosuppression). Some older liver transplant recipients can actually drop their immunosuppression drugs completely.

The exact transplant protocol also influences long-term levels of immunosuppression and thus cancer risk.

Yes, but not just from the transplant. The immunosuppressant drugs following a transplant also increase your risk of cancer. Dramatically for certain types of cancers.

Well sure, more risk than an individual, less risk than two individuals.