A histologic study of extralobar pulmonary sequestration and its anomalous artery as a clue to its development.

In 1997, an anomalous small mass of soft tissue was found in the left thoracic cavity of a Japanese male cadaver during student dissection practice. It was linked only by branches from the thoracic aorta, hemiazygos vein and greater splanchnic nerve, with no connection to the normal lung by vessels or airway. Examination of cut sections clarified that this anomalous small tissue mass was an extralobar pulmonary sequestration (EPS). Many cases of pulmonary sequestration have been reported from the clinical aspect, but there are few from a purely anatomical viewpoint. In the present case, detailed gross anatomical and histologic observations clarified that the anomalous artery supplying the sequestration resembled an elastic artery. In view of the findings of other reports, the anomalous arteries are divided into two types, the elastic type such as the pulmonary artery and the muscular type such as the bronchial artery. So it is thought that the histologic observation of an anomalous artery in comparison with normal pulmonary and bronchial arteries may offer an important clue to consider in elucidating the origin and development of pulmonary sequestration.