A British man said he figured out something was wrong when he opened a FedEx package expecting an Amazon Kindle, but instead got a box marked “Human Specimen.”

FedEx apologized for the delivery mistake, BBC reported Sunday. The box apparently contained a patient’s tumor.

James Potten told the news agency FedEx had called him on Thursday claiming a worker had tried to make the delivery earlier in the day at his home in Bristol, west of London. Potten said he’d returned home, so the worker came back with the package.

“The tracking code on the item had the same first five and last three numbers as my order but it wasn't my Kindle,” Potten said.

He told BBC he never opened the box. London’s Royal Free Hospital claimed it was supposed to be delivered there.

A FedEx spokesman said the company "will consider future changes to our processes.”

Potten finally got his Kindle on Sunday.