Fig. 3

Histological finding of the cyst resected at the previous operation. a, b Small epithelial tumor nodules and lymphoid stroma which resemble Fig. 2a, b exist in the cyst wall (arrow). There is a layer of squamous and cuboidal epithelial cells that line the wall (arrowhead). c–e The immunostaining patterns of the secondary resected thymic tumor and the previously resected cyst are the same, so the cyst is re-diagnosed as cystic lesion of micronodular thymoma with lymphoid stroma. HE hematoxylin and eosin stain