Clinicopathologic features and lymph node metastatic characteristics in patients with adenocarcinoma manifesting as part-solid nodule exceeding 3 cm in diameter.

Purpose: The purpose of this study was to elucidate the clinicopathologic and lymph node metastatic characteristics in patients with adenocarcinoma manifested as persistent ground glass mass (GGM, ground glass opacity [GGO] exceeding 3 cm in diameter). Materials and

Methods: 304 patients with adenocarcinoma manifested as persistent GGM > 3 cm, who underwent complete surgical resection between November 2013 and December 2017 were included in this study. We elucidated the lymph node metastatic incidence and characteristics according to the primary tumor lobe location and extracted the associated clinicopathological factors, especially thin-section computed tomographic findings, with lymph node involvement.

Results: All of the GGMs were invasive adenocarcinoma in histopathology. The total incidence of lymph node metastasis was 2.0% (6/304). All of the 6 cases with hilar or mediastinal lymph node metastasis were manifested as solid-predominant GGM > 3 cm and no cases with lymph node metastasis were identified in GGO-predominant GGM > 3 cm. Lymph node metastases were more likely to present in younger patients (p = 0.032), tumors with solid size >2.0 cm (p = 0.000), more advanced clinical T stage (p = 0.000), radiological solid-predominant tumors (p = 0.002) and acinar-predominant or papillary-predominant adenocarcinoma (p = 0.002). As for solid-predominant GGMs >3 cm, lymph node metastases were more likely to be found in tumors with solid size >2.0 cm (p = 0.026), more advanced clinical T stage(p = 0.026), acinar-predominant or papillary-predominant adenocarcinoma (p = 0.029). Whole tumor size was not associated with the presence of lymph node metastases. There were 2 right upper-lobe cases with upper mediastinal lymph nodes skip metastasis without intrapulmonary, interlobar, and hilar lymph node metastasis.

Conclusion: All of the GGMs >3 cm were invasive adenocarcinoma. The incidence of lymph node metastasis in GGO-predominant GGMs >3 cm was extremely low. Solid size would be a better predictor of lymph node metastasis than whole tumor size in sold-predominant GGMs >3 cm.