Fig. 3

Morphological features of the tumor. A, The tumor was composed of branched papillae with fibrovascular cores, and partial papillary cores hyalinized (100×). B, The fibrovascular core was infiltrated with lymphocytes and histiocytes, cilia can be seen (200×). C, The tumor protruded into the surrounding lung tissue in a mushroom-shaped without pro-fibrointerstitial reaction around (40×). D, The tumor cells were crowded and arranged pseudostratified with obvious nucleoli (400×)