Background: Lung cancer is the leading cause of cancer related death worldwide. More than 80% of all lung tumors are Non-Small Cell Lung Cancers (NSCLC). Lymph node staging has a prognostic value and is crucial to establish the optimal treatment strategy in individual patients. It remains unknown whether dissecting the intrapulmonary lymph nodes (stations 13 and 14) is necessary for accurate staging and prognostication. Although suggested by several guidelines, these peripheral lymph nodes are not routinely examined in clinical routine for several reasons. Moreover, the prognostic significance of the visceral pleural invasion is controversial. Some studies showed a negative impact on OS and DFS in patients with histologic proved visceral pleura invasion.

The mechanism to explain this negative effect is not fully understood. Given that the visceral pleura is very rich in lymphatic vessels, with an intercommunicating "network" arranged over the lung surface and penetrating into the lung parenchyma to join the bronchial lymph vessels with drainage to the various hilar nodes, we assume that the worse OS and DFS observed in these patients could be explained with the presence of metastatic lymph nodes (Station 13-14) that are not routinely examined. Methods: This is a prospective, multicenter study based on ad-hoc created prospectively database. The incidence of N1 lymph node metastasis overall and the incidence of metastasis to the different lymph node stations (Hilar 10/11, Lobar 12, Sublobar 13/14) will be calculated by dividing the number of the respective events by the patient years separately. To investigate the association between visceral pleural invasion and the presence of metastatic lymph nodes univariate and multivariate logistic regression models will be fitted to the data.

Discussion: The primary outcome is to investigate the incidence of N1 metastases (especially stations 12,13,14) and his relationship with visceral pleural invasion. The secondary outcomes is to evaluate the impact of N1 metastases and/or visceral pleural invasion on long-term outcomes (OS and DFS) along with incidence and pattern of recurrence. DFS is defined as the time of surgical intervention to tumor recurrence or death, and OS is defined as the time of surgical intervention to death

Inclusion Criteria:

• Anatomical resection for NSCLC <3 cm (lobectomy, bilobectomy, segmentectomy)
• Samples from the intrapulmonary stations 12, 13, and 14 lymph nodes
• Resection of lymphnodes station 10 and 11 during hilar separation.
• R0 resection

Exclusion Criteria:

• Prior or synchronous lung cancer
• pN2
• Pneumonectomy
• R1/R2 resection
• M1
• Neoadjuvant treatment

Patients recorded prospectively in the database from January 2023 to December 2024 that meet the inclusion and exclusion criteria