The Azygos lobe

NEJM features a case of azygos lobe with fissure along with metastatic nodule from osteogenic sarcoma, check out images and case details here-
NEJM-Azygos lobe


What is azygos lobe?

"Abnormal fissures and lobes of the lungs are common and usually insignificant. A lobe of the azygos vein appears in the right lung in about 1 percent of people. It develops when the apical bronchus grows superiorly medial to the arch of the azygos vein instead of lateral to it. As a result, the azygos vein comes to lie at the bottom of a deep fissure in the superior lobe of the right lung."