A comprehensive literature search using the keywords “lung adenosquamous carcinoma” and “pulmonary adenosquamous carcinoma” was conducted across PubMed, CNKI, and other academic databases to identify pivotal studies and clinical reports on treatment outcomes and prognosis ( Table 1 ). Analysis demonstrated that during the conventional therapy era (surgery with radiotherapy/chemotherapy), patients achieved progression-free survival (PFS) of 5.7-14 months, median overall survival (OS) of 13.8-34.7 months, and 5-year survival rates of 9.0%-37% (5, 6, 17–19, 21, 24) across all tumor stages. In the immunotherapy era, immune checkpoint inhibitors (ICIs; nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab) significantly improved outcomes: PFS increased by 6.0-7.7 months and median OS extended to 8.8-24.7 months (11, 20, 23). These findings collectively underscore the aggressive biological behavior of this malignancy, characterized by high recurrence risk, early metastatic dissemination, and poor long-term prognosis.

This study presents the first documented case of advanced adenosquamous carcinoma harboring co-occurring driver mutations (KRAS p.G12C, BRAF p.G466R (non-V600E), PIK3CA p.H1047R, FLT1 p.L1232F). The tumor demonstrated PD-L1 positivity (TPS = 18.11%), tumor mutational burden (TMB) of 3.7 muts/Mb, and microsatellite instability-low (MSI-L, 35.29%). Following first-line therapy with tislelizumab plus platinum-based doublet chemotherapy, the patient achieved sustained complete radiological response (RECIST v1.1, Response Evaluation Criteria in Solid Tumors version 1.1) with unprecedented progression-free survival (PFS) exceeding 46.5 months, which surpassed all published outcomes for this aggressive NSCLC subtype. This paradigm-shifting case provides compelling evidence for durable disease control through PD-1 blockade in molecularly complex adenosquamous carcinomas.

Given to its epidemiologic rarity and consequent scarcity of molecularly annotated cohorts, ASC remains inadequately characterized regarding clonal origin, clinicopathological features, and prognostic determinants, gene landscape and treatment strategy.

The clonal origin of ASC remains a subject of ongoing debate in thoracic oncology (25, 26). Current research employs multi-region whole-exome sequencing to clarify its histogenetic ambiguity. Studies have proposed two main hypotheses regarding its clonal evolution: 1. Polyclonal origin: Some researchers suggest that ASC arises from distinct progenitor cells, with adenocarcinoma (ADC) and squamous cell carcinoma (SCC) developing independently during early tumorigenesis and subsequently infiltrating each other as the tumor progresses (27). 2. Monoclonal origin: Other studies, employing molecular analyses of hotspot mutations, propose that ASC originates from a single common progenitor cell. This view is supported by evidence that adenocarcinoma (ADC) and squamous cell carcinoma (SCC) share common driver mutations, such as EGFR and KRAS alterations, indicating a shared clonal lineage (2, 24, 28–30). While the debate continues, advancements in genomic sequencing techniques are helping to resolve these conflicting hypotheses and provide deeper insights into the molecular mechanisms underlying ASC.

Although adenosquamous carcinoma (ASC) is defined by its biphasic composition of adenocarcinoma (ADC) and squamous cell carcinoma (SCC) components, it exhibits more aggressive biological behavior than either component alone (16, 31, 32). Furthermore, the clinicopathological characteristics and prognosis of ASC differ significantly from those of pure ADC or SCC (33, 34). The clinical characteristics of adenosquamous carcinoma (ASC) show heterogeneity across studies. Most studies (35, 36) report higher tumor grade in ASC compared to adenocarcinoma (ADC) and squamous cell carcinoma (SCC). However, In the study by Maeda and colleagues (7), ASC patients had a lower tumor grade, compared with ADC patients, but there was no significant difference between ASC and SCC patients. Studies report conflicting findings regarding ASC tumor size: Mordant et al. (16) suggested ASC has the largest tumor size among the three subtypes, while others (6, 35) reported an intermediate size between ADC and SCC. Similarly, data on lymph node metastasis rates are inconsistent. Some studies indicate ASC exhibits higher rates than ADC (7, 35), while others suggest rates intermediate between ADC and SCC. However, one study (35) found the proportion of nodal metastasis in ASC patients was slightly lower than that in ADC and SCC patients (35). Multiple studies concur that ASC is often diagnosed at more advanced stages. Maeda et al. (7) specifically reported a significantly higher prevalence of stage IIIA disease in ASC compared to ADC. Furthermore, studies by Wang et al. (6) and Nakagawa et al. (36) demonstrated a higher incidence of pleural invasion in ASC patients. Multiple studies concur that ASC is often diagnosed at more advanced stages. Maeda et al. (7) specifically reported a significantly higher prevalence of stage IIIA disease in ASC compared to ADC. Furthermore, studies by Wang, et al. (6) and Nakagawa et al. (36) demonstrated a higher incidence of pleural invasion in ASC patients. Contradictory conclusions also exist regarding tumor grade and size (e.g., Cooke vs. Maeda on grading) (7, 36). Relatively consistent trends in advanced staging, higher lymph node metastasis rates, and elevated pleural invasion incidence suggest that ASC exhibits a more aggressive phenotype than either ADC or SCC. ASC is generally characterized as an aggressive mid-to-late-stage malignancy with poorer differentiation. However, discrepancies in specific features (e.g., tumor grade, size) across studies may stem from variations in sample size or population demographics, warranting larger-scale validation studies. The prognosis of ASC remains debated, although most studies suggest poorer survival compared to ADC and SCC. Filosso et al. (37) reported 3- and 5-year postoperative survival rates of 25% and 15% for ASC, significantly worse than ADC/SCC. Gawrychowski et al. (8) observed similarly dismal outcomes, with 5- and 10-year survival rates of 25.4% and 19.2% post-surgery, confirming ASC’s poorer prognosis. Cooke, et al. (35), analyzing 872 surgically treated ASC cases from the SEER database (1998–2002), reinforced the inferior survival of ASC relative to ADC/SCC. In contrast, Uramoto, et al. (38) and Hsia, et al. (39) found no significant survival difference between ASC, ADC, and SCC. Although a study by Wang et al. (34) initially suggested a better prognosis for ASC, subsequent stratified analyses contradicted this finding, revealing worse survival for ASC in both surgical and non-surgical subgroups. While the preponderance of evidence highlights an unfavorable survival profile for ASC compared to ADC/SCC, these conflicting results underscore the need for further large-scale studies to clarify prognostic trends and elucidate the underlying pathophysiological mechanisms.

Rapid advances in biotechnology have led to the identification of numerous oncogenes, inhibitors targeting these driver mutations have demonstrated encouraging efficacy (40–46). Pulmonary adenosquamous carcinoma (ASC), a rare lung cancer subtype, exhibits pathological features of both adenocarcinoma (ADC) and squamous cell carcinoma (SCC), and harbors a molecular profile combining characteristic driver mutations from both subtypes. Pulmonary adenosquamous carcinoma (ASC), a rare lung cancer subtype, exhibits pathological features of both ADC and SCC, and harbors a molecular profile combining characteristic driver mutations from both subtypes. Systematic molecular profiling of ASC could elucidate key mechanisms underlying phenotype switching, tumor origin, and heterogeneity, while guiding personalized therapeutic strategies. In pulmonary adenosquamous carcinoma, the incidence of EGFR mutations is relatively high, though lower than that in lung adenocarcinoma. Previous studies report EGFR mutation rates in ASC ranging from 13% to 57.6% across Western and Chinese populations (29, 30, 47–50). Notably, a study of 28 immunohistochemistry (IHC)-validated Asian ASCs revealed a markedly higher EGFR mutation rate of 79%, accompanied by mutations in TP53 (68%), MAP3K1 (14%), EGFR amplification (32%), and MDM2 amplification (18%), among others (51). The observed variability in EGFR mutation frequency may stem from factors such as sample selection bias, ethnic differences, tobacco exposure, or pathological misdiagnosis. Deletions in exon 19 and the L858R mutation are the most common EGFR mutation types. And the EGFR T790M mutation has been documented, typically arising as an acquired resistance mechanism following EGFR tyrosine kinase inhibitor (EGFR-TKI) therapy. Furthermore, the incidence of EGFR mutations is higher in non-smokers. Wang et al. observed EGFR mutations in 83.72% (36/43) of non-smokers compared to only 25% in smokers. This suggests that the high proportion of EGFR-mutated patients is attributable to the higher prevalence of non-smokers. Interestingly, retrospective studies have shown that EGFR-TKIs therapy is effective for patients with advanced non-small cell lung cancer, with response rates ranging from 26.5%to 40.7%, and median progression-free survival (PFS) ranging from 4.3 to 15.0 months (47–49, 52, 53)

KRAS mutations are also reported in pulmonary adenosquamous carcinoma (ASC), although their incidence is considerably low compared to EGFR mutations, occurring in approximately 5%-15% of ASC cases (54). The G12C substitution is the predominant KRAS mutation subtype in ASC and is strongly associated with smoking. KRAS mutations generally portend a poorer prognosis. For patients with ASC harboring a KRAS G12C mutation, first-line treatment with sotorasib represents a feasible therapeutic option. Sotorasib, a KRAS G12C inhibitor developed by Amgen (a US pharmaceutical company), received accelerated approval from the US Food and Drug Administration (FDA) on May 28, 2021, for the treatment of KRAS G12C-mutant non-small cell lung cancer (NSCLC) (55). However, it has not yet been approved by China’s National Medical Products Administration (NMPA) and remains in Phase III clinical trials. Therefore, the drug is currently unavailable for direct purchase in China. Fortunately, it has been reported that the KRAS gene is associated with the efficacy of immunotherapy (56, 57).

BRAF mutations are generally associated with aggressive tumor behavior and poor prognosis, regardless of mutation type. Patients with BRAF-mutant tumors often demonstrate limited efficacy to traditional chemotherapy and immunotherapy (58, 59).

While BRAF mutations are rare in NSCLC, occurring in approximately 2% of lung adenocarcinoma cases (60). The combination of dabrafenib (a BRAF inhibitor) and trametinib (a MEK inhibitor) is the first globally approved targeted regimen for advanced BRAF V600E-mutant NSCLC. Clinical trials demonstrated its efficacy as first-line therapy, achieving an objective response rate (ORR) of 64%, median progression-free survival (PFS) of 14.6 months and median overall survival (OS) of 24.6 months (61). Based on this evidence, China’s National Medical Products Administration (NMPA) approved this combination for metastatic NSCLC in March 2022. For tumors with BRAF non-V600E mutations, individualized therapeutic strategies remain under exploration. The advent of BRAF inhibitors (BRAFi) and immune checkpoint inhibitors (ICIs) has transformed the treatment landscape for BRAF-mutant NSCLC (62). However, specific studies on BRAF mutations in pulmonary adenosquamous carcinoma remain scarce. The exact incidence of BRAF mutations in ASC is unclear, and current understanding are largely extrapolated from adenocarcinoma data.

PIK3CA is a family of lipid kinases that plays an important role in regulating cell growth, proliferation, and survival. The PIK3CA mutation rate in NSCLC is 2–5%, 8–10% in lung squamous cell carcinoma (SCC), and 2.8% in adenocarcinoma (ADC) (63). These mutations are generally regarded as co-alterations rather than primary driver mutations. However, their presence, particularly as concomitant mutations, is associated with poor treatment response and shorter survival time (64, 65). In pulmonary adenosquamous carcinoma (ASC), PIK3CA mutations appear relatively common, although reported incidence rates exhibit significant variability across studies (25). The application of PIK3CA inhibitors in lung cancer treatment remains under active investigation. Nevertheless, emerging clinical studies and case reports suggest potential therapeutic value for some agents (66, 67). Immunotherapy has also been used to treat patients with PIK3CA mutations, but the PI3K/AKT pathway has been reported to be associated with immunotherapy resistance (68).

The FLT1 gene encodes a receptor tyrosine kinase that belongs to the vascular endothelial growth factor receptor (VEGF) family. Members of this family possess tyrosine protein kinase activity, which is critical for controlling cell proliferation and differentiation. The structure of FLT1 includes seven identical immunoglobulin domains in the extracellular region, a transmembrane domain, and a tyrosine kinase (TK) domain in the cytoplasmic region. FLT1 exhibits high-affinity binding to VEGF, VEGF-B, and PIGF and is associated with tumor invasion. Mutations in this gene, including missense mutations, nonsense mutations, silent mutations, and frameshift deletions, have been identified in colorectal cancer, skin cancer, and gastric cancer (69–72). However, no such mutations have been reported in pulmonary adenosquamous carcinoma.

The rapid development of immune checkpoint inhibitors (ICIs) has profoundly transformed the management of various cancer. Advances in cancer immunotherapy, particularly programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors, has profoundly transformed the management of various cancers and significantly reshaped standard treatment paradigms for non-small cell lung cancer (NSCLC) The rapid development of immune checkpoint inhibitors (ICIs), particularly programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors, has profoundly transformed the management of various cancer and significantly reshaped standard treatment paradigms for non-small cell lung cancer (NSCLC) (11, 13). For advanced KRAS-mutant NSCLC, multiple studies have demonstrated that patients receiving immunotherapy exhibit relatively favorable median progression-free survival (mPFS) and median overall survival (mOS), with limited correlation to PD-L1 expression levels. For instance, a single-center retrospective cohort study reported a median PFS of 16.2 months and median OS of 31.3 months in KRAS-mutant advanced NSCLC patients treated with immune checkpoint inhibitors (ICIs) as first-line therapy (73). Furthermore, the IMpower150 trial indicated that atezolizumab combined with bevacizumab and chemotherapy remains an effective treatment regimen for KRAS-mutant NSCLC patients, irrespective of the presence of STK11, KEAP1, or TP53 co-mutations. These findings collectively suggest that the KRAS G12C mutation may serve as a predictive biomarker for immunotherapy efficacy (74). Furthermore, studies have found that immunological biomarkers such as PD-L1 and high tumor mutational burden (TMB) are associated with favorable responses to immune checkpoint inhibitors (ICIs) (75, 76). In conclusion, immune checkpoint inhibitors (ICIs, PD-L1/PD-1 inhibitors) may serve as a potentially effective treatment option for ASC patients with KRAS G12C mutations and PD-L1 positive.

This study presents the first report of a pulmonary ASC case harboring co-occurring KRAS p.G12C, BRAF p.G466R (non-V600E), PIK3CA p.H1047R and FLT1 p.L1232F mutations that demonstrated a remarkable response to immune checkpoint inhibitors (ICI), challenging the conventional notion that “multiple driver mutations equate to immune resistance”. Our findings highlight the complexity of tumor heterogeneity and its interplay with immunotherapy efficacy. Despite the absence of ASC-specific recommendations in current guidelines, personalized combination strategies (e.g., ICI plus chemotherapy) guided by molecular profiling may overcome traditional therapeutic limitations. Future studies should prioritize accumulating multi-omics data from similar cases, establishing a dedicated biomarker framework for pulmonary ASC to advance precision medicine in this aggressive malignancy.