Histologic Patterns of Metastatic Lymph Nodes and Recurrence Patterns in Resected pN1-2 Lung Adenocarcinoma.

AIMS: Histologic grading of the primary tumor (PT) is an established prognostic factor in lung adenocarcinoma; however, the clinical relevance of histologic patterns in metastatic lymph nodes (MLNs) remains unclear. This study investigated whether MLN histology is associated with recurrence patterns after complete resection. METHODS: We retrospectively analyzed 120 patients with pN1-2 lung adenocarcinoma who underwent complete resection at a single institution. Predominant histologic patterns of PTs and MLNs were categorized as low grade (lepidic), intermediate grade (papillary or acinar), or high grade (solid or micropapillary) according to the IASLC histologic grading system. Survival outcomes and recurrence patterns (locoregional vs distant) were compared across MLN histologic groups. RESULTS: Predominant histologic patterns were frequently discordant between PTs and MLNs (McNemar test, P = 0.01; κ = 0.25). High-grade PTs were associated with significantly shorter recurrence-free survival (RFS) than intermediate-grade tumors (P = 0.02), whereas MLN histology was not associated with RFS (P = 0.70). PT histology was not significantly related to recurrence site. In contrast, intermediate-grade MLNs showed a significantly higher incidence of locoregional recurrence than high-grade MLNs (P = 0.04), which was confirmed by cumulative incidence analysis (P = 0.02). Distant recurrence rates were comparable between the two groups (P = 0.39). CONCLUSIONS: While histologic grading of the primary tumor reflects overall tumor aggressiveness and prognosis, the histologic architecture of metastatic lymph nodes may be associated with recurrence patterns rather than survival outcomes. These findings suggest that MLN morphology may provide complementary pathological information regarding patterns of locoregional recurrence after surgical resection.