STRUCTURE OF THE INITIAL LYMPHATICS OF THE HUMAN URINARY-BLADDER WITHINVASIVE UROTHELIAL TUMORS

The ability of urothelial tumors of the urinary bladder to metastasize via the lymphatic circulation and the extent of metastatic involvemen t of regional lymph nodes is an important parameter in the staging and prognosis of these neoplasms. Accordingly, we examined the site and m orphology of initial lymphatic vessels in the mucosa of the human urin ary bladder in patients with invasive transitional cell carcinoma. Lym phatics in the papillary tumoral mass was also examined. Endoscopic tr ansurethral biopsies from the urinary bladder of 120 patients with inv asive transitional cell papillary carcinoma were utilized for this stu dy. Biopsy from the uninvolved lateral wall of the same patient was ut ilized as a control. On histopathology of biopsies of neoplastic tissu es, initial lymph vessels were seen in the deeper region of the mucosa but not in the subepithelial layer nor in the stroma of the tumoral p apillae. The latter were often associated with arteriolar and venular vessels. When edema and inflammation occurred in peritumoral regions, lymphatics showed a dilated lumen, non-indented wall with dissociated perivascular collagen and elastic fibers. Tumoral permeation or emboli zation of lymphatics was seen in 12% of patients with invasive tumors, and these lymphatic vessels did not display significant morphologic c hanges. The absence of initial lymphatics in the stroma of tumoral pap illae and in infiltrated subepithelial regions of the urinary bladder may explain the absence of lymph node metastasis in early-stage invasi ve urothelial tumors.