Lymphatic vascular density and lymphangiogenesis during tumor progression of carcinoma ex-pleomorphic adenoma

Abstract

Aims: To assess lymphatic vascular density (LVD) and lymph vessel endothelial proliferation in a series of carcinoma ex pleomorphic adenoma (CXPA) that represents the tumor in the different carcinogenesis phases and tumor progression.

Methods: In 8 cases of early CXPA (intracapsular and minimally invasive tumors), 8 of advanced CXPA (widely invasive tumors) and 10 of pleomorphic adenoma (PA) without malignant transformation, lymphatic vessels and proliferating cells were detected using the antibodies D2-40 and Ki 67 respectively.

Results: Comparing early tumors with advanced ones, LVD was not significantly different at the tumor margin. In contrast, regarding intratumoral lymphatics, PA without malignant transformation and early CXPA contained rare, if any, lymph vessels whereas in widely invasive carcinomas they were more numerous. However, neither intratumoral nor peritumoral LVD were increased in comparison to adjacent normal salivary gland tissue. In no case did dual immunohistochemistry using D2-40 and the cell proliferation marker Ki-67 reveal the existence of proliferating lymphatics. Carcinomatous emboli were found in peritumoral as well as in intratumoral lymphatics only in advanced CXPA without myoepithelial differentiation.

Conclusion: In CXPA, the lymphatic network is mainly composed of pre-existing lymphatics which are rare in tumors that have not infiltrated outside the confines of the original PA. In the widely invasive CXPA, intratumoral as well as peritumoral lymphatics are a conduit for carcinoma cells, but in carcinomas with myoepithelial differentiation, the neoplastic cells seem to have a lower invasion capacity.