According to the World Health Organization (WHO), lung cancer is among the most common malignancies worldwide and remains the leading cause of cancer-related deaths. In 2022, approximately 2.1 million new cases were reported globally, and about 1.8 million individuals died from the disease [[1], [2], [3]]. Such high incidence and mortality rates make lung cancer a major concern for both global health systems and oncologic research.

Non-small cell lung carcinomas (NSCLCs) account for the majority of lung cancers, with adenocarcinoma representing the most frequent histological subtype, comprising 40 % of all cases [4]. Traditionally, the spread of lung adenocarcinomas has been described through lymphatic, hematogenous, and direct invasion pathways. However, in 2015, Kadota et al. [5] identified a novel pattern of tumor spread termed “spread through air spaces – STAS”. In the 5th edition of the WHO Classification of Thoracic Tumors, STAS is defined as tumor cells found within air spaces in the lung parenchyma beyond the edge of the main tumor and is morphologically categorized into three subtypes: micropapillary structures, solid nests, and discohesive single cells [4]. Initially studied in adenocarcinomas, STAS has subsequently gained importance as a phenomenon also investigated in other lung cancer types [6].

Following Kadota's definition, the morphological patterns of STAS were described in more detail, and additional classifications emerged, characterizing STAS either by distance (limited vs. extensive STAS) or by the number of foci and cluster density (low vs. high-level STAS) [7,8]. Numerous studies have demonstrated that the presence of STAS is associated with increased tumor aggressiveness and serves as an independent adverse prognostic factor [5,9]. Nevertheless, the majority of these investigations have focused primarily on the mere presence or absence of STAS. Its underlying mechanism remains poorly understood, and only a limited number of studies have addressed the prognostic impact of histologic parameters such as morphological subtype, extent, and density.

In this study, we evaluated STAS morphological subtypes, extent, and density in lung adenocarcinomas, and analyzed their relationship with clinicopathologic features and survival outcomes. By assessing these parameters in a large surgical resection cohort, our aim was to address existing gaps in the literature and highlight the prognostic significance of STAS from multiple perspectives, with a particular focus on its potential implications for clinical management.