A 13-month-old male with secondary pulmonary vein stenosis due to total anomalous pulmonary venous connection repair who presented with hypoxemia. (A) Axial contrast-enhanced thoracic MDCT angiography CT image shows ill-defined, mildly heterogeneously enhancing, non-calcified soft tissue mass (asterisk) in the expected location of the left proximal pulmonary vein. Left proximal pulmonary vein is absent. Similar abnormal soft tissue (arrowheads) surrounding left pulmonary vein with decreased size is seen more distally. Right pulmonary vein (RPV) is patent. LA = left atrium. (B) Coronal contrast-enhanced thoracic MDCT angiography CT image demonstrates ill-defined, mildly heterogeneously enhancing, non-calcified soft tissue mass (arrowheads) along the narrowed left pulmonary vein. Right pulmonary vein (RPV) is patent. (C) 3D volume-rendered vascular reconstruction CT image in the posterior projection view shows absent left pulmonary vein in the expected location (asterisk). Patent right pulmonary vein (RPV) is seen. DA = descending aorta. (D) Pulmonary vein biopsy obtained at age 14 months shows circumferential intimal fibromyxoid proliferation (left panel; original magnification, 20×) and extravascular/adventitial foreign-body giant-cell reaction (not shown), fibrosis, and a cellular inflammatory infiltrate comprised of lymphocytes, plasma cells, eosinophils, and histiocytes (right panel; original magnification, 40×). Hematoxylin and eosin stain in both images.