Fig. 4

A low-power view of the tumor tissue by bronchoscopy and biopsy (a), metastatic tumor cells are beneath the respiratory epithelium of the trachea (b), A high-power view shows round and polygonal tumor cells with sprinkled small lymphocytes infiltration (c), similar to those occurring in the bladder. Immunohistochemically, the tumor cells are negative for CK (d), positive for CD21 (e) and focal positive for CD23 (f)