Mother-to-infant transmission of cancer is extremely rare. Researchers report two cases of lung cancer in children caused by the transmission of cervical tumors from the mothers.

A 23-month-old boy, who had been delivered vaginally after his mother tested negative for cervical cancer, presented with a productive cough. A computed tomographic scan showed multiple masses along the bronchi in both lungs. A lung biopsy revealed neuroendocrine carcinoma of the lung. The lesions progressed one year after diagnosis. Although some lesions had spontaneously regressed, tumor masses were seen in both lungs, and chemotherapy was administered. Some tumors shrank, but others progressed. Comparison of the gene profiles in samples of tumor and normal tissue showed that the child's tumor was due to transmission of the mother's tumor and contained genes that weren't in the child's germline genome. A pathological complete response was indicated after 14 cycles of nivolumab and a lobectomy. The child had no evidence of disease recurrence 12 months after lobectomy.

The second patient, a six-year-old boy, had also been delivered vaginally. He presented with chest pain, and computed tomography revealed a mass in the left lung. Mucinous adenocarcinoma was diagnosed. After several cycles of chemotherapy, he underwent total left pneumonectomy and was disease-free 15 months later. As in the first case, gene profiles of tumor samples from the mother and child indicated mother-to-child transmission.

The likely mode of transmission was aspiration of tumor cells from the mother's amniotic fluid, secretions, or cervical blood. Though rare, these cases indicate that transmission of cancer is possible during vaginal delivery. Therefore, the authors recommend cesarean section for mothers who have uterine cervical cancer.