Angiogenic and lymphangiogenic profiles in histological variants of papillary thyroid carcinoma

Introduction.  Papillary thyroid carcinoma (PTC) is a well‑differentiated
tumor that occurs in several histological variants whose biological behaviors remain unclear. Angiogenesis and lymphangiogenesis are critical processes that enable tumor progression.
Objectives. The aim of this study was to evaluate the angiogenic and lymphangiogenic phenotypes of PTC, considering the differences between histological variants.
Patients and methods.  Angiogenic and lymphangiogenic profiles were analyzed by determining microvascular density (MVD) and lymphatic vessel density (LVD) in 73 cases of PTC, using immunohistochemistry. To assess the biological markers involved in blood and lymph vessel formation, the expression of vascular endothelial growth factor (VEGF), cyclooxygenase 2 (COX‑2),
and p27kip1 (p27) was determined. Results. MVD was significantly higher in patients with high‑risk
PTC and in those with local extrathyroidal and vascular invasion. Positive VEGF expression was strongly associated with high MVD and age‑related tumor enlargement. The presence of lymph vessel invasion was associated with the expression of either VEGF or COX‑2. The analysis of angiogenesis and lymphangiogenesis in different histological variants of PTC revealed elevated LVD rather than MVD in the follicular variant of PTC (FV‑PTC). Lower MVD was observed in FV‑PTC relative to the classic variant of PTC (CV‑PTC). The frequency of VEGF‑positive tumors was higher in CV‑PTC than in FV‑PTC. A significant association between COX‑2 and p27 expression was observed in FV‑PTC but not in CV‑PTC.
Conclusions. These results suggest that VEGF, COX‑2, and p27 may be important biological markers
that determine the angiogenic and lymphangiogenic potentials of PTC, particularly between the follicular
and classic variants.