Surprised surgeons performing a lung cancer operation apparently found a 5cm fir tree growing inside the patient.

The Daily Mail reports doctors thought Russian man Artyom Sidorkin, 28, had a tumour after he complained of extreme pain in his chest and had been coughing up blood.

The x-ray image shows what looks like a large tumour in his lung.

During the operation, surgeon Vladimir Kamashev said he thought he was hallucinating when he saw the fir tree needles inside the tissue.

Medical staff said the 5cm tree is too big to be swallowed and believe Mr Sidorkin had inhaled a seed which later sprouted.

“It was very painful. But to be honest I did not feel any foreign object inside me,” said Mr Sidorkin. “I’m so relieved it’s not cancer.”

credited to news.com.au