Prognostic Value of Lymphovascular Space Invasion and Its Quantification in Endometrial Carcinoma in Northern Thailand.

OBJECTIVE: To evaluate the prognostic performance of lymphovascular space invasion (LVSI) quantification in patients with endometrial carcinoma (EC). METHODS: Clinical and pathological data from EC patients who underwent primary surgical treatment between January 2008 and December 2020 were analyzed. Five-year progression-free survival (PFS) and overall survival (OS) were compared across LVSI categories (absent, focal, substantial) using previously proposed thresholds for substantial LVSI (≥3, ≥4, or ≥5 involved spaces). RESULTS: A total of 843 patients were included (mean follow-up, 9.5 years). All three thresholds (3, 4, or 5 spaces) yielded significant differences in PFS and OS across LVSI categories (absent, focal, and substantial; p < 0.001). After adjustment for established clinicopathologic prognostic factors, substantial LVSI remained independently associated with worse PFS and OS compared with absent LVSI (PFS: p = 0.005-0.007; OS: p = 0.002-0.006). Focal LVSI, defined as <4 or <5 spaces, showed a trend toward lower adjusted PFS compared with absent LVSI, although the difference did not reach statistical significance (p = 0.052-0.059). For OS, focal LVSI showed worse adjusted outcomes than absent LVSI when using the <5-space definition (p = 0.024). No significant adjusted differences in PFS or OS were observed between focal and substantial LVSI. CONCLUSION: Substantial LVSI (at least 3 involved spaces) is strongly associated with poorer prognosis in EC. Additionally, focal LVSI may be linked to decreased survival. These findings underscore the prognostic value of LVSI quantification and support further investigation into the clinical relevance of focal LVSI.