Lung tumors derived from ectopic tissues.

Ectopic tissues rarely occur in the lung. They include endometriosis, neurological tissue, thyroid, pancreas, and adrenal. Choristomas are very rare developmental anomalies derived from these ectopic tissues. They develop as a mass composed of histologically normal tissues that are heterotopic in the lung. Various intrapulmonary neoplasms also rarely develop from ectopic tissues. They include malignant melanoma, thymoma, meningioma, glomus tumor, germ cell neoplasms (choriocarcinoma and teratoma), and ependymoma. The clinicopathological features of these unusual pulmonary neoplasms are discussed.