Radiologic phenotype and the size dependence of adverse histologic features and recurrence in resected lung adenocarcinoma

Objectives The eighth edition TNM classification measures part-solid lung adenocarcinoma by the solid component alone. We examined whether CT-measured size carries the same pathologic and prognostic meaning in part-solid and solid adenocarcinoma. Materials and methods We retrospectively analyzed 3857 consecutive patients with resected non-mucinous lung adenocarcinoma (2011–2022), using phenotype and size from preoperative CT reports. Shape-constrained additive models estimated the size-dependent prevalence of seven adverse features, including high-grade (HG) patterns, micropapillary component and spread through air spaces (STAS). Five-year cumulative incidence of recurrence (CIR) was estimated with death as a competing risk. Results Tumors were part-solid in 2100 and solid in 1757 patients. In part-solid tumors, HG patterns, micropapillary component and STAS rose most steeply at 1.25–1.36 cm of total size (0.85–0.93 cm of solid component); in solid tumors, HG patterns and STAS were already frequent at the smallest measured sizes. Lymphovascular, pleural and nodal involvement became prevalent at larger sizes in both phenotypes. Among 3580 patients analyzed for recurrence (467 recurrences; median follow-up, 56.6 months), solid tumors had higher CIR than part-solid tumors within each matched solid-component size stratum (feature-present tumors > 2.5 cm: 42.7% vs 19.6%). In part-solid tumors, 5-year CIR was 1.4% when HG morphology was the most advanced feature, 11.0% with local invasion and 50.0% with nodal involvement. Conclusions Measuring the solid component narrows but does not close the difference in pathologic risk between part-solid and solid adenocarcinoma of the same size. These associations warrant external validation and evaluation in preoperative risk models.