Abstract
The metastatic risk profile of microscopic lymphatic and venous invasion in
medullary thyroid cancer is ill-defined. This evidence gap calls for evaluation
of the suitability of microscopic lymphatic and venous invasion at thyroidectomy
for prediction of lymph node and distant metastases in medullary thyroid cancer.
In this study of 484 patients with medullary thyroid cancer who had≥5
lymph nodes removed at initial thyroidectomy, microscopic lymphatic and venous
invasion were significantly associated with greater primary tumor size (27.6 vs.
14.5 mm, and 30.8 vs. 16.2 mm) and more frequent lymph node
metastasis (97.0 vs. 25.9%, and 85.2 vs. 39.5%) and distant
metastasis (25.0 vs. 5.1%, and 32.8 vs. 7.3%). Prediction of
lymph node metastases by microscopic lymphatic invasion was better than
prediction of distant metastases by microscopic venous invasion regarding
sensitivity (97.0 vs. 32.8%) and positive predictive value (58.4 vs.
39.2%); comparable regarding negative predictive value (98.5 vs.
90.5%) and accuracy (80.4 vs. 85.1%); and worse regarding
specificity (74.1 vs. 92.7%). On multivariable logistic regression,
microscopic lymphatic invasion predicted lymph node metastasis better (odds
ratio [OR] 65.6) than primary tumor size (OR 4.6 for
tumors>40 mm and OR 2.7 for tumors 21–40 mm,
relative to tumors≤20 mm), whereas primary tumor size was better
in predicting distant metastasis (OR 8.3 for tumors>40 mm and OR
3.9 for tumors 21–40 mm, relative to
tumors≤20 mm) than microscopic venous invasion (OR 3.2). These
data show that lymphatic invasion predicts lymph node metastases better in
medullary thyroid cancer than venous invasion heralds distant metastases.
Key words
medullary thyroid carcinoma - lymphatic invasion - venous invasion - lymph node metastases
- distant metastases
