Four transplant patients who received a heart, a liver and two kidneys were unaware that their donor had suffered from a tumour - but experts said their risk of contracting any disease was negligible.
A pair of unused corneas from the same donor would be destroyed to prevent further worries by recipients, a Hospital Authority spokesperson said.
The benign tumour found in the donor's thymus, an organ of the immune system, raised only a remote risk to the organ recipients, she said.
The donor, a 51-year-old woman, died from a stroke on Monday in Queen Elizabeth Hospital. On examination, her heart, liver, both kidneys and pair of corneas were considered suitable for organ transplantation.
It was only when the donor's organs were being removed that the tumour of was discovered.
It was examined and considered benign, and after further risk assessment, doctors felt the organs were suitable for donation.
The woman's donated organs went to four patients.
The heart was transplanted into a 51-year-old male cardiac patient, and, on Tuesday, a liver graft went to a 38-year-old man in a hepatic coma in Queen Mary Hospital.
The kidneys were transplanted into two female renal patients, a 41-year-old at Queen Elizabeth Hospital and a 54-year-old at Queen Mary Hospital.
The cardiac patient died yesterday, Queen Elizabeth Hospital said.
Detailed results of tissue examination made available on Wednesday showed that the rare type of tumour, known as a thymoma, was at an early stage of development.
The hospitals said they had met the patients and relatives to discuss follow-up plans.
Dr Daniel Chua Tsin-tien, a radiotherapist at Hong Kong Sanatorium and Hospital, said the health risks to the organ recipients were low.
'If the donor suffers from a cancer, there is always a risk of passing on malignant cells,' Chau said.
'In this case, the organs most at risk are the liver and lungs, as they are nearer to the thymus. But as we are talking about a benign tumour, the health risk is very low - almost none.'