Histologic changes: This low-power view of the wall of the resected lung nodule shows an epithelial-lined cyst that is surrounded by connective tissue (arrows indicate the junction with adjacent lung, which is unremarkable). The epithelial lining is the same as that seen in the lymph node. It has been shown in some cases that the spindled cells of the "stroma" are keratin-positive suggesting that they are epithelial elements of the yolk sac tumor and not reactive stroma. Their presence does not mean, however, that further therapy is necessary [2].

Case 2--Diagnosis 1Image 10