It was meant to be a package containing a new Kindle, not a human tumour sample.
But when British man James Potten opened what he thought was a waterproof Kindle, instead he found an item intended for London's Royal Free Hospital.
The mix up by courier company FedEx was reportedly due to similar tracking numbers on the two packages.
Potten, 37, told the BBC: ""When I opened it I had quite a shock.
"I've been trying to get FedEx to collect it as it is potentially a sample that needs to be tested and sent back with some urgency. I don't know where my Kindle is, but if it is at the Royal Free I'd be happy to do an exchange."
FedEx responded saying it regretted the error and will look at reviewing their processes.
The tumour was reportedly redirected to the hospital while Potten announced via Twitter the arrival of his Kindle.