Tumor-Associated Lymphatic and Venous Vessels in Medullary Thyroid Carcinomas

Tatsuo Tomita

doi:10.4236/ojpathology.2015.52008

Abstract

Objective: Medullary thyroid carcinomas (MTCs) invade local lymph node through lymphatic vessels and metastasize to distant organs hematogenously and account for a significant mortality. There are possibly increased lymphatic and venous vessels, through which the tumor spreads to lymph nodes and distant organs. Materials and Methods: By immunocytochemical staining for lymphatic and venous vessels, MTC lesions with adjacent normal thyroid and both normal and metastatic lymph nodes were studied for the peritumoral lymphatic and venous vessels, which were morphometrically compared with those of normal thyroid and lymph nodes. Sixteen cases of MTC cases with adjacent thyroid tissues and attached lymph nodes were immunocytochemically stained for lymphatic vessels using lymphatic vessel hyaluronan receptor (LYVE-1) and venous vessels for factor VIII (F-8). The immunostained sections of MTC lesions and metastatic lymph nodes were morphometrically compared for the number and sizes of the vessels with those of normal thyroid tissues and lymph nodes. Results: Significantly increased lymphatic vessels and markedly increased blood vessels were identified in many MTC cases at the peritumoral tissues and metastatic lymph nodes whereas a few lymphatic vessels and no venous vessels were identified in midst of MTCs. The irregular peritumoral lymphatic vessels resembled that of immature lymphatic vessels observed in papillary thyroid carcinomas and increased irregularly, entrapped venous vessels in peritumoral tissues resembled those observed in follicular thyroid carcinomas. Conclusion: The significantly increased lymphatic vessels and markedly increased venous vessels in the peritumoral thyroid tissue support a propensity of MTCs for providing an easy access of tumor cells to both lymphatic spread to the regional lymph nodes and venous spread to distant organs with further tumor spread through metastatic lymph nodes by moderately increased lymphatic and venous vessels.

Highlights

Medullary thyroid carcinomas (MTCs) are relatively rare tumors, representing about 3% - 10% of all thyroid carcinomas but account for significant mortality with overall prognosis of 60% - 70% of 10 year survival rate [1][2]
The significantly increased lymphatic vessels and markedly increased venous vessels in the peritumoral thyroid tissue support a propensity of MTCs for providing an easy access of tumor cells to both lymphatic spread to the regional lymph nodes and venous spread to distant organs with further tumor spread through metastatic lymph nodes by moderately increased lymphatic and venous vessels
There was a strong association between the intratumoral lymphatic vessels and regional lymph node metastases for papillary thyroid carcinomas, suggesting that and there were numerous slender to enlarged round venous vessels at the peripheral tumor zone (D). (A) and (C): proliferation and invasion of new lymphatic vessels into the tumor play a role in its spread through lymphatic vessels [4]

Summary

Introduction

MTCs invade regional lymph nodes and spread hematogenously to distant organs, lungs, liver and bones, which are the major cause of death [2]. Machens and Dralle analyzed 715 cases of MTC and found that 10%, 8% and 5% were diagnosed with lung, liver and bone metastasis, respectively [3]. MTCs account for 80% of the carcinomas whereas 20% have a familial basis [5] [6]. Both papillary and follicular carcinomas reportedly showed increased lymphatic vessels and venous vessels, respectively: papillary carcinomas revealed increased lymphatic vessels using lymphatic vessel endothelial hyluronan receptor (LYVE-1)

Methods

Results

Conclusion