The lymphatic system in clinically localized urothelial carcinoma of the bladder: morphologic characteristics and predictive value.

OBJECTIVE

To assess the lymphatic vessel density (LVD) and lymphangiogenesis in urothelial carcinoma of the bladder (UCB) and to identify predictors of progression in patients treated by transurethral resection (TUR).

MATERIALS AND METHODS

One hundred eleven patients who underwent TUR for UCB were retrospectively included. Lymphatic endothelial cells were stained immunohistochemically [D2-40 (podoplanin) antibody in all samples; Prox-1, LYVE-1, and VEGFR-3 (Flt-4) in subgroups]. LVD was measured in representative intratumoral (ITLVD), peritumoral (PTLVD), and nontumoral (NTLVD) areas using standardized criteria. Double-immunostainings with D2-40/CD-34 were performed to distinguish between blood and lymphatic vessels, and D2-40/Ki-67 stainings were done to detect lymphangiogenesis. Lymph-specific parameters were correlated with pathologic and clinical characteristics. In patients with non-muscle-invasive UCB (n = 76) univariable and multivariable analyses were performed to identify predictors of progression.

RESULTS

The PTLVD was significantly higher than ITLVD and NTLVD (P < 0.001). Proliferating lymphatic vessels were observed in all specimens assessed with D2-40/Ki-67. Characteristic suburothelial D2-40 positivity was observed in noninvasive pTa tumors. LYVE-1-stainings revealed the existence of tumor-associated macrophages. The presence of intratumoral lymphatic vessels was significantly associated with higher tumor stage, high grade, and sessile growth (all P < 0.001). Muscle-invasive tumors (P = 0.020), higher grade (P = 0.026), the presence of lymphovascular invasion (P < 0.001), and concomitant carcinoma in situ (CIS) (P = 0.020), sessile growth (P = 0.004), and loss of suburothelial D2-40 positivity (P = 0.031) were associated with disease progression in univariable analysis. LVD values in any area were not significantly associated with progression despite detection of proliferating lymphatic vessels. The presence of concomitant CIS was identified as an independent predictor of progression on multivariable analysis (P = 0.041; hazard ratio 4.620).

CONCLUSIONS

A high peritumoral LVD is present in clinically localized UCB. The presence of intratumoral lymphatic vessels correlates with characteristics of aggressive disease. Lymphangiogenesis occurs; however, the lymph-specific parameters tested in this study cannot be used to predict progression following TUR. The presence of concomitant CIS is an important risk factor for later disease progression in patients with non-muscle-invasive UCB. Our results contribute to the understanding of metastatic tumor spread in UCB.