Two children with lung cancer in Japan acquired the tumor cells from their mothers during or shortly before birth – an incredibly rare way of developing the disease.
Chitose Ogawa of the National Cancer Center Hospital in Tokyo and her colleagues made the discovery when they were sequencing the DNA of the children’s tumors for a prospective clinical study.
The first boy was diagnosed with lung cancer at 23 months of age, while the second boy was 6 years old when he developed chest pain, which led doctors to discover a tumor in his left lung.
Both mothers had cervical cancer: the mother of the first boy was diagnosed three months after birth, and the mother of the second boy was diagnosed after delivery.
The analysis revealed that the boys ‘tumors had genetic mutations that matched those of their mothers’ cancers.
It was also shown that the DNA of the boys’ tumor cells lacked the Y chromosome found in most male cells. The cells also tested positive for strains of the human papillomavirus – which are known to cause cervical cancer.
Some cancer cells likely got into the amniotic fluid during late pregnancy or were transferred to the children during their birth, says Paul Ekert of the Sydney Children’s Cancer Institute, who was not involved in the research. Both children were born vaginally and it is possible that they inhaled tumor cells.
Such cases of mother-to-child transmission of cancer are surprisingly rare. Approximately one in 1000 live births affects a mother with cancer. It is estimated that one baby in every 500,000 mothers with cancer will transmit it.
Most childhood cancer specialists could see it once in a lifetime, says Ekert, an expert on pediatric oncology. “Ordinarily, this would be mitigated because of immune surveillance for contamination of cells from another individual – even if that individual is related,” he says.
Even more unusual is the fact that a boy didn’t show symptoms until he was 6 years old, he adds. This suggests that the cancer cells persisted for years and slowly divided before growing faster.