German researchers who sought to determine the metastatic risk profile in medullary thyroid cancer (MTC) concluded that “lymphatic invasion predicts lymph node metastases better in medullary thyroid cancer than venous invasion heralds distant metastases.”
To evaluate the “suitability of microscopic lymphatic and venous invasion at thyroidectomy” to predict lymph node and distant metastases in MTC, a team led by Henning Dralle, professor of surgery and surgery department chairman at the University of Halle-Wittenberg, analyzed 484 patients with MTC who had 5 or more lymph nodes removed at initial thyroidectomy between November 1994 and March 2021 at a tertiary surgical center dedicated to thyroid cancer.
Of those, 45 had sporadic disease and 139 had hereditary diseases. Research has shown that sporadic and hereditary MTC do not differ in terms of metastatic behavior.
The researchers found that “microscopic lymphatic and venous invasion were significantly associated with greater primary tumor size” and more frequent lymph node and distant metastases.
They also found that the prediction of lymph node metastases by microscopic lymphatic invasion was better than the prediction of distant metastases by microscopic venous invasion, in terms of sensitivity and positive predictive value. The 2 approaches were comparable in terms of negative predictive value and accuracy. In terms of specificity, the prediction of lymph node metastases by microscopic lymphatic invasion was worse than the prediction of distant metastases by microscopic venous invasion.
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Statistical analyses revealed that microscopic lymphatic invasion predicted lymph node metastasis better than primary tumor size. Primary tumor size, on the other hand, was better in predicting distant metastasis than microscopic venous invasion.
“These real-life data strongly support separation of lymphatic from vascular invasion in MTC,” the researchers wrote. They added that more research is needed to optimize clinical follow-up and explore the role of adjuvant therapy in patients with angioinvasive MTC.
Machens A, Lorenz K, Weber F, Dralle H. Metastatic risk profile of microscopic lymphatic and venous invasion in medullary thyroid cancer. Horm Metab Res. 2021;53(9):588-593. doi:10.1055/a-1559-3424