Fetal Lung Interstitial Tumor

**Semantic type:** Neoplastic Process

**Definition:** A congenital benign tumor of lung interstitial mesenchymal cells that presents with respiratory symptoms in neonates. Images reveal a well-circumscribed solid or partially cystic lung mass. Microscopical examination reveals widened alveolar septa that contain bland, uniform mesenchymal cells. Some cases show ALK rearrangement and A2M-ALK gene fusion.

**Synonyms:** - FLIT