Azygos_lobe
In human anatomy, an azygos lobe is a normal anatomical variation of the upper lobe of the right lung.[1] It is seen in 0.3% of the population.[2] Embryologically, it arises from an anomalous lateral course of the azygos vein,[3] in a pleural septum within the apical segment of the right upper lobe or in other words an azygos lobe is formed when the right posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers as the azygous fissure, that invaginates into the upper portion of the right upper lobe.[1]