Genomic and Transcriptomic Landscape of Spread Through Air Spaces in Stage 1 Lung Adenocarcinoma

One of the most consequential findings in modern lung cancer pathology is also one of the hardest to see with the naked eye. Spread through air spaces, abbreviated STAS, describes tumor cells that have detached from the main mass of a lung adenocarcinoma and drifted into the tiny air-filled alveoli surrounding it. These microscopic satellites are invisible on CT scans, undetectable by surgeons, and yet they carry profound implications: patients whose stage 1 lung adenocarcinomas show STAS face a substantially higher risk of recurrence after surgery, particularly when only a limited resection is performed. For more than a decade, pathologists have documented the phenomenon and oncologists have adjusted treatment plans around it, but a fundamental question has remained stubbornly open. What, biologically, is STAS? Is it simply a random shedding of tumor cells into adjacent airspaces, or is it the visible signature of a distinct molecular program that equips certain cancers to disperse early in their evolution?

A new study published in the British Journal of Cancer sets out to answer that question at the level of the genome and the transcriptome, providing the most detailed molecular portrait to date of spread through air spaces in early-stage lung adenocarcinoma. By systematically comparing the genomic and transcriptional features of tumors with and without STAS, and in some cases by interrogating the disseminated tumor cells themselves, the researchers have begun to transform STAS from a purely morphological observation into a biologically defined state. The work suggests that STAS is not an accident of anatomy but the product of specific molecular alterations and gene expression programs that may be targetable in the clinic.

The clinical stakes could hardly be higher. Lung adenocarcinoma is the most common histological subtype of lung cancer worldwide, and with the widespread adoption of low-dose CT screening, an ever-growing number of patients are diagnosed with small, apparently curable stage 1 tumors. For these patients, surgery offers the best chance of a cure, and the past two decades have seen a determined effort to reduce the extent of that surgery. Sublobar resections, including wedge resections and segmentectomies, preserve lung function and are increasingly offered for small tumors. But the landmark JCOG0802 and CALGB 140503 trials, which supported sublobar resection for selected small adenocarcinomas, also highlighted a critical caveat: tumors that have spread through airspaces behave differently. Intraoperative frozen-section analysis for STAS is now recommended in many centers precisely because finding STAS in a limited specimen argues for a full lobectomy and, increasingly, for adjuvant therapy. Understanding the biology behind STAS could refine these decisions even further.

To build their molecular portrait, the study team assembled a cohort of resected stage 1 lung adenocarcinomas that had been exhaustively reviewed by expert pathologists for the presence and extent of STAS. Genomic DNA extracted from tumor tissue was subjected to targeted next-generation sequencing, allowing the researchers to catalog the mutations, copy-number changes and mutational signatures present in each tumor. In parallel, RNA sequencing was used to define the transcriptional landscape, capturing not only the cancer cells themselves but also the stromal and immune cells of the tumor microenvironment. Where feasible, the investigators enriched for or microdissected the STAS tumor cell clusters, so that the molecular features of the disseminated cells could be compared directly with those of the main tumor mass from which they arose.

The genomic results revealed that STAS-positive tumors are not genomically identical to their STAS-negative counterparts. Certain patterns of alteration were enriched among tumors that had spread through airspaces, hinting that particular driver events may predispose adenocarcinomas to this mode of early dissemination. Copy-number analysis added a further layer of insight, with STAS-positive tumors showing evidence of greater genomic instability, the kind of chromosomal chaos that is typically associated with aggressive behavior and metastatic competence. Mutational signatures, the fossil records of past mutational processes, provided additional clues about the evolutionary history of these tumors and the timing at which the capacity for airspace spread may have been acquired.

The transcriptomic findings were, if anything, more striking. Gene expression profiling identified coherent transcriptional programs that distinguish STAS-positive tumors, including signatures consistent with epithelial-mesenchymal transition, the cellular program by which epithelial cancer cells loosen their attachments, gain motility and acquire invasive properties. The analysis also pointed to altered cell adhesion, remodeling of the extracellular matrix, and changes in pathways governing cell survival under the hypoxic, nutrient-poor conditions of the alveolar space. In other words, the tumor cells that float free in airspaces appear to have activated a molecular toolkit that helps them detach, survive in transit and potentially re-establish themselves at distant sites. This is precisely the toolkit that classical metastasis research has implicated in the spread of cancer through blood and lymphatic vessels, and seeing it engaged in airspace spread strengthens the argument that STAS is a genuine early step in the metastatic cascade rather than a passive artifact.

Equally important were the findings concerning the tumor microenvironment. The RNA sequencing data allowed the researchers to deconvolute the cellular composition of STAS-positive and STAS-negative tumors, and the comparison revealed differences in the immune landscape. Tumors with airspace spread showed alterations in immune cell infiltration and in the expression of immune-related genes, suggesting that the local immunological milieu may either permit or restrain the escape of tumor cells into airspaces. If confirmed and refined, this observation could have direct therapeutic implications, because the immune checkpoint inhibitors that have transformed the treatment of advanced lung cancer are now being tested and deployed in earlier disease stages. A molecular understanding of STAS could help identify which patients with early-stage disease are most likely to benefit from perioperative immunotherapy.

The study also speaks to a long-running debate about the mechanism of STAS. Some investigators have argued that tumor cells found in airspaces are dislodged during surgical handling, a concern that has shadowed the field since STAS was first described. The molecular data argue against a purely artifactual explanation. If STAS cells were merely mechanical debris, one would not expect them to be associated with reproducible genomic and transcriptomic differences at the level of the parent tumor, nor with coherent biological programs of dissemination and survival. The convergence of morphological, genomic and transcriptomic evidence instead supports the view that STAS reflects an intrinsic property of a subset of adenocarcinomas, one that is written into their molecular makeup before the surgeon ever touches the lung.

The implications for clinical practice are considerable. Today, STAS is assessed by pathologists examining hematoxylin and eosin stained slides, a process that is inherently subjective, dependent on sampling, and impossible to perform prospectively on imaging. A molecular definition of STAS, or a biomarker panel that predicts which tumors are likely to show airspace spread, could allow preoperative risk stratification using biopsy material. Patients whose tumors carry the molecular signature of STAS could be directed toward lobectomy and systemic therapy from the outset, while those without it could safely undergo lung-preserving limited resections. Conversely, the identification of specific altered pathways in STAS-positive tumors raises the possibility of targeted interventions designed specifically to block airspace dissemination, an avenue that has barely been explored until now.

There are, of course, caveats. Stage 1 lung adenocarcinoma is a heterogeneous disease, and STAS itself can be patchy, making sampling a persistent challenge for any molecular study that relies on bulk tissue. The transcriptional programs identified in this work will need validation in independent, larger cohorts, ideally with single-cell resolution to determine exactly which cells within the tumor carry the dissemination program and how the STAS cell clusters differ from their parent clones. Prospective studies will be needed to test whether molecular STAS signatures outperform or complement histological assessment in predicting recurrence. Nevertheless, the study represents a decisive step forward. By mapping the genomic and transcriptomic landscape of spread through air spaces, it converts a century-old pathological observation into a modern biological question with testable mechanisms, measurable biomarkers and plausible therapeutic answers. For the growing population of patients diagnosed with small, early-stage lung adenocarcinomas, that transformation may ultimately determine whether their surgery is curative or merely the first chapter in a longer disease course.

Subject of Research: Genomic and transcriptomic characterization of spread through air spaces in stage 1 lung adenocarcinoma

Article Title: Genomic and transcriptomic landscape of spread through air spaces in stage 1 lung adenocarcinoma

Article References: Saw, S. P. L., Pang, M., Patteri, C., Takano, A., Yeo, J. C., Sim, N. L., Lai, G. G. Y., Lim, D. W. T., Ang, M.-K., Kanesvaran, R., Ng, Q. S., Jain, A., Tan, W. L., Tan, A. C., Tan, W. C., Seet, A. O. L., Ong, B.-H., Lim, T. K. H., Skanderup, A. J., & Tan, D. S. W. (2026). Genomic and transcriptomic landscape of spread through air spaces in stage 1 lung adenocarcinoma. British Journal of Cancer. https://doi.org/10.1038/s41416-026-03622-8

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03622-8

Keywords: lung adenocarcinoma, spread through air spaces, STAS, genomics, transcriptomics, stage 1 lung cancer, tumor microenvironment, single-cell analysis, cancer metastasis, biomarkers, surgical pathology, prognosis