A RARE cancer that affected 20 known patients worldwide struck two Singaporean women over the past week.

Ms Angela Lee, 37, a sub-editor with the Singapore Press Holdings' Special Projects Unit, came down with it in March last year, after a lump - the size of a tennis ball - was found on her back.

She died on Valentine's Day last Thursday.

According to her brother, Mr Eugene Lee, 40, a lawyer, the cancer was aggressive.

'It was diagnosed as skin cancer in March last year and she underwent six weeks of radiotherapy,' he said.

Ms Lee, who was single, suffered a relapse in November.

'A scan showed the cancer had spread. It had eaten away one of her vertebrae and spread into her chest cavity. It was downhill from there,' Mr Lee said.

The Straits Times understands that another patient is currently being treated at the National Cancer Centre for the same cancer.

It had started in her uterus and she was transferred from KK Women's and Children's Hospital to the National Cancer Centre.

The patient underwent surgery and is undergoing targeted therapy that attacks the specific cancer cells.

According to medical literature, it is more common among women - with a sex ratio of 4:1.

Dr Alvin Wong, a consultant with the department of haematology-oncology at the National University Hospital (NUH), said most often, PEComa is benign or non-cancerous. The malignant version is rare, with only 20 medically recorded.

A Google search drew up 45 cases worldwide - making the two Singapore cases the 46th and 47th.

Read the full story in today's edition of The Straits Times.