STRUCTURE OF THE INITIAL LYMPHATICS OF THE HUMAN URINARY BLADDER WITH INVASIVE UROTHELIAL TUMORS

Abstract

The ability of urothelial tumors of the urinary bladder to metastasize via the lymphaticcirculation and the extent of metastatic involvement of regional lymph nodes is an importantparameter in the staging and prognosis of these neoplasms.. Accordingly, we examined the siteand morphology of initial lymphatic vessels in the mucosa of the human urinary bladder inpatients with invasive transitional cell carcinoma. Lymphatics in the papillary tumoral mass wasalso examined. Endoscopic transurethral biopsies from the urinary bladder of 120 patients withinvasive transitional cell papillary carcinoma were utilized for this study. Biopsy from theuninvolved lateral wall of the same patient was utilized as a control. On histopathology ofbiopsies of neoplastic tissues, initial lymph vessels were seen in the deeper region of the mucosabut not in the subepithelial layer nor in the stroma of the tumoral papillae. The latter were oftenassociated with arteriolar and venular vessels. When edema and inflammation occurred inperitumoral regions, lymphatics showed a dilated lumen, non-indented wall with dissociatedperivascular collagen and elastic fibers. Tumoral permeation or embolization of lymphatics wasseen in 12% of patients with invasive tumors, and these lymphatic vessels did not displaysignificant morphologic changes. The absence of initial lymphatics in the stroma of tumoralpapillae and in infiltrated subepithelial regions of the urinary bladder may explain the absenceof lymph node metastasis in early-stage invasive urothelial tumors.