Rhabdomyosarcoma of lung arising in congenital cystic adenomatoid malformation.

An asymptomatic congenital cystic adenomatoid malformation of lung discovered at age 18 months, and unchanging for 14 months prior to its removal, was found to harbor a small embryonal rhabdomyosarcoma following excision. With lobectomy and chemotherapy, the tumor-free interval has now exceeded three years. The case represents a well-documented occurrence of malignant tumor arising within a congenital malformation, an association that is unlikely to be the result of chance.