Although rare, a variety of heterotopic tissues in the lung have been described, including striated muscle, adrenal tissue, thyroid, pancreas, and liver. Glial tissue has also been observed uncommonly. Most cases are associated with anencephaly or other open neural tube defects, presumably from fetal aspiration of brain tissue in utero.

Rhabdomyomatous dysplasia is a rare phenomenon that consists of diffuse infiltration of striated muscle fibers within the interstitium of the lung. It is always seen in association with some other pulmonary developmental abnormality, particularly extralobar sequestration and less commonly cystic adenomatoid malformation and other abnormalities. It has also been reported in association with complex cardiopulmonary malformations. Alternate names in the literature include adenorhabdomyoma, hemangiorhabdomyoma, rhabdomyomatoid dysplasia, and diffuse heteroplasia of striated muscle.