Endobronchial Ultrasound guided biopsy (EBUS) is increasingly used to diagnose and stage patients with suspected lung malignancy. Previous studies have demonstrated diagnostic yields of close to 90% and similar yields have been shown for both molecular and PDL1 testing. However, the current biomarkers we have at our disposal are imperfect. The importance of the human microbiome in health and disease is a novel field that has exploded in the last few years. The gut microbiome has been shown to affect treatment response to immunotherapy in non-small cell lung cancer (NSCLC) and the lower respiratory tract (LRT) and oral microbiome have been demonstrated to predict recurrence in surgically resected NSCLC.

The binding of programmed death ligand-1 (PD-L1) to its receptor PD-1, on the surface of activated T cells, inhibits cytotoxic T cell responses. Immune checkpoint inhibitors target this mechanism, improving outcomes for patients with non-small cell lung cancer (NSCLC). Stratifying patients based on their PD-L1 IHC (immunohistochemistry) expression score informs response rates. We investigated the prevalence of PD-L1 IHC expression in a real-world Australian setting, retrospectively collecting patient demographics, clinical and pathological data.

Key gene alterations during carcinogenesis include defects in DNA mismatch repair mechanisms that can be identified in tumours indirectly by analysing tandem DNA repeats or microsatellites. 'Elevated microsatellite alterations at selected tetranucleotide repeats' (EMAST) is a more recent form of microsatellite instability, first described in lung cancer in 1994 (Mao et al 1994, doi.org/10.1073/pnas.91.21.9871). EMAST has been closely linked to MSH3 protein deficiency or dysfunction in colorectal cancer but its significance in lung cancer is poorly understood.

Neoadjuvant therapies have unique advantages and opportunities in lung cancer but also present some challenges; including a lack of established guidance on how to process and evaluate resected lung cancer specimens in both clinical practice and clinical trials. The IASLC provided guidance for specimen processing and is now conducting this interobserver study for PR evaluation.

NSCLC is associated with an increasing number of molecularly defined subsets, several of which now have approved targeted therapies. Variation in how different biomarker assays are utilised is likely. We sought to determine the current biomarker testing practices from the perspective of medical oncologists (MO) and pathologists (P) at Australian sites to understand variations in practice and potential influencing factors.

Recognizing invasion in pulmonary adenocarcinomas is important since, in the 8th edition of UICC/AJCC TNM classification system, the primary tumor T stage is determined based on presence and size of the invasive components. The aim of this study was to identify histological features in tumors with lepidic growth pattern that may be used to establish criteria for distinguishing invasive from non-invasive areas.

Non-small cell lung cancer (NSCLC) comprises approximately 85% of patients diagnosed with metastatic disease,1Testa U. Castelli G. Pelosi E. Lung cancers: molecular characterization, clonal heterogeneity and evolution, and cancer stem cells.Cancers (Basel). 2018; 10: 248Crossref PubMed Scopus (183) Google Scholar of which the major histological subtypes are adenocarcinoma (ADC) and squamous cell carcinoma (SCC).2WHO Classification of Tumours Editorial BoardThoracic tumours.in: Borczuk A.C. Cooper W. Dacic S. WHO Classification of Tumours. 5th ed. IARC, Lyon2021Google Scholar These tumour types are thought to originate from different cell types, typically arise in different locations within the lung, express differing molecular alteration profiles and are variably associated with tobacco exposure. Lung ADC are thought to arise from alveolar type II cells, bronchoalveolar stem cells, or club cells,3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar are more often located distally, and have been identified to harbour a variety of therapeutically targetable oncogenic molecular alterations involving genes such as EGFR, ALK, ROS1, RET, BRAF, MET, NTRK, TP53 and HER2. In contrast, SCCs are typically more centrally located, arising from basal cells in bronchiolar epithelium,3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar and harbour mutations in genes such as TP53, CDKN2A, PTEN, PIK3CA, KEAP1, MLL2, and NFE2L2.1Testa U. Castelli G. Pelosi E. Lung cancers: molecular characterization, clonal heterogeneity and evolution, and cancer stem cells.Cancers (Basel). 2018; 10: 248Crossref PubMed Scopus (183) Google Scholar Most patients with SCC will have a prior smoking history, whereas a subset of patients with ADC have minimal or no cigarette exposure and these adenocarcinomas are associated with mutations of EGFR (approximately 47% in Asia-Pacific NSCLC/ADC cohorts4Midha A. Dearden S. McCormack R. EGFR mutation incidence in non-small-cell lung cancer of adenocarcinoma histology: a systematic review and global map by ethnicity (mutMapII).Am J Cancer Res. 2015; 5: 2892-2911PubMed Google Scholar and 15% in Western cohorts).5Mead S. Lucas M. Pang J.-M. et al.EGFR mutation profile in Australian patients with non-small cell lung cancer.Pathology. 2021; 53: 933-936Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar Adenosquamous carcinomas (ADSC) are rare NSCLCs (2–3% of lung cancers) which by definition include at least 10% of both ADC and SCC in resection specimens.2WHO Classification of Tumours Editorial BoardThoracic tumours.in: Borczuk A.C. Cooper W. Dacic S. WHO Classification of Tumours. 5th ed. IARC, Lyon2021Google Scholar They may occur in non-smokers and may harbour similar oncogenic driver mutations to lung ADC2 but can be difficult to diagnose in small biopsy samples and sampling bias may lead to misclassification as either ADC or SCC. Amongst EGFR-mutated lung ADC treated with EGFR tyrosine kinase inhibitors (TKIs), transformation to small cell carcinoma is a recognised mechanism of treatment resistance.1Testa U. Castelli G. Pelosi E. Lung cancers: molecular characterization, clonal heterogeneity and evolution, and cancer stem cells.Cancers (Basel). 2018; 10: 248Crossref PubMed Scopus (183) Google Scholar Emerging within the literature is the recognition that squamous differentiation/transformation may also be a potential mechanism of treatment resistance; either due to true ADC to SCC transition (AST),3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar or clonal selection that has occurred in the context of initial ADSC histology. We describe two intriguing cases from our institution, with initial ADC and ADSC histology harbouring an oncogenic driver mutation and subsequent development of predominant SCC differentiation on re-biopsy at progression. Case 1 was a 55-year-old life-long never-smoker of South-East Asian ethnicity, who was diagnosed with de novo metastatic NSCLC in June 2018 with radiological evidence of a lung primary, lymphangitis carcinomatosis, bilateral thoracic node involvement and a single 4 mm brain metastasis. At diagnosis, fine needle biopsy of a supraclavicular fossa lymph node demonstrated metastatic adenocarcinoma histology (TTF1+, p40–), a programmed death ligand-1 (PDL-1) tumour proportion score (TPS) of 10%, with an ALK translocation confirmed by fluorescence in situ hybridisation (Fig. 1A–C). Following stereotactic radiosurgery to the brain metastasis she commenced treatment with the ALK TKI crizotinib via a clinical trial. In December 2018, at intra-cranial progression, she proceeded to second-line alectinib, an ALK directed TKI. In July 2021 she underwent biopsy of a newly enlarged axillary lymph node, which revealed a keratinising SCC with occasional cells demonstrating intracytoplasmic mucin, and immunohistochemistry (IHC) profile consisting of p40+, TTF1– (Fig. 1D–H), and preserved ALK translocation on IHC. Subsequently, a progressing isolated brain metastasis was resected in December 2021, with evidence of adenocarcinoma and squamous components and ALK alteration preserved. Case 2 was a 52-year-old life-long never-smoker of Caucasian ethnicity, who was diagnosed with de novo metastatic NSCLC in December 2018, with baseline imaging demonstrating a lung primary, regional lymphadenopathy and bilateral lung and skeletal metastases. Surgical biopsy of a femoral lesion during orthopaedic intervention revealed metastatic carcinoma demonstrating predominant ADC (acinar and cribriform architecture, TTF1+) with a small focus (approximately 5–10%) of squamous morphology (p40+, cytokeratin 5/6+), raising the possibility of ADSC (Fig. 2A–F). An EGFR exon 19 deletion was detected and PDL-1 TPS was 3%. First-line systemic therapy was commenced with erlotinib, a first generation EGFR TKI. In September 2019 at progression a liver biopsy demonstrated TTF1+ adenocarcinoma harbouring an EGFR T790M resistance mutation. Second-line osimertinib, a third generation anti-EGFR TKI, was commenced until progression in July 2020. A further biopsy of a liver lesion demonstrated metastatic adenocarcinoma, TTF1+. The patient commenced third-line treatment with platinum-doublet chemotherapy (carboplatin/pemetrexed) in combination with doublet immunotherapy [durvalumab, a PDL-1 inhibitor; and tremelimumab, a cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) inhibitor] via clinical trial until progression in July 2021 (ILLUMINATE trial NCT03994393). Hip lesion core biopsies demonstrated metastatic keratinising SCC (p40+/TTF1–) with no evidence of glandular differentiation. Repeat mutation testing revealed preservation of the original EGFR exon 19 deletion with no T790M mutation detected. Subsequent treatment response with trial anti-EGFR therapy was noted (Fig. 2G,H). Whilst development of small cell lung cancer histology is a well described but uncommon mechanism of TKI resistance in metastatic lung ADC, morphological change involving subsequent development of SCC histology has been rarely reported.3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar Amongst the just over 20 cases described to date, the majority have been recognised to harbour an EGFR mutation at initial diagnosis, which have been preserved at re-biopsy with some harbouring a T790M mutation.3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar To our knowledge, only five cases of ALK-translocated cases have been reported with subsequent SCC differentiation: one after progression on crizotinib;6Wang F. Qin J. Xie F. et al.Transformation of EML4-ALK fusion-positive adenocarcinoma into squamous cell carcinoma in association with acquired resistance to crizotinib.Lung Cancer. 2020; 140: 118-120Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar one after exposure to crizotinib, ceritinib and alectinib;7Gong J. Gregg J.P. Ma W. et al.Squamous cell transformation of primary lung adenocarcinoma in a patient with EML4-ALK fusion variant 5 refractory to ALK inhibitors.J Natl Compr Canc Netw. 2019; 17: 297-301Crossref PubMed Scopus (13) Google Scholar one after exposure to alectinib;8Kaiho T. Nakajima T. Iwasawa S. et al.ALK rearrangement adenocarcinoma with histological transformation to squamous cell carcinoma resistant to alectinib and ceritinib.Onco Targets Ther. 2020; 13: 1557-1560Crossref PubMed Scopus (9) Google Scholar one after alectinib and crizotinib;9Park S. Han J. Sun J.M. Histologic transformation of ALK-rearranged adenocarcinoma to squamous cell carcinoma after treatment with ALK inhibitor.Lung Cancer. 2019; 127: 66-68Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar and one heavily pre-treated patient with prior exposure to cytotoxic therapy, multiple ALK-directed TKIs including most recently lorlatinib.10Ueda S. Shukuya T. Hayashi T. et al.Transformation from adenocarcinoma to squamous cell lung carcinoma with MET amplification after lorlatinib resistance: a case report.Thorac Cancer. 2021; 12: 715-719Crossref PubMed Scopus (5) Google Scholar Whether the phenomenon is more likely to occur in patients with EGFR-mutated NSCLC compared to ALK-translocated NSCLC is difficult to surmise given the relatively lower incidence of ALK-translocations (approximately 3–7% of patients diagnosed with metastatic NSCLC),11Itchins M. Chia P.L. Hayes S.A. et al.Treatment of ALK-rearranged non-small cell lung cancer: A review of the landscape and approach to emerging patterns of treatment resistance in the Australian context.Asia Pac J Clin Oncol. 2017; 13: 3-13Crossref PubMed Scopus (9) Google Scholar and re-biopsy at progression may be less common than for EGFR-mutated cases. The fact that EGFR and ALK alterations are preserved despite morphological change from initial ADC to SCC in cases illustrating this phenomenon in the literature, suggests a phenomenon of ADC to SCC transition (AST). In ADSC cohorts, the identification of oncogenic drivers in both the ADC and SCC components has likewise been suggested to support the notion of AST.1Testa U. Castelli G. Pelosi E. Lung cancers: molecular characterization, clonal heterogeneity and evolution, and cancer stem cells.Cancers (Basel). 2018; 10: 248Crossref PubMed Scopus (183) Google Scholar Observational data from case reports for AST is further supported by Chen et al., who described loss of the LKB1 gene in genetically engineered mouse models harbouring KRAS G12D mutations as being associated with development of AST.3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar The authors also note the role of YAP, a transcriptional co-factor, which acts as an oncogenic driver in the case of lung ADC, whereas it exerts a tumour suppressor function in SCC, suggesting that additional understanding of the function of YAP may contribute to greater understanding of AST.3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar It is unclear whether the cases presented represent true AST or clonal selection in the context of initial ADSC histology, such as for Case 2, and the implications for subsequent clinical management. Whether future treatment should be guided by SCC rather than ADC histology is unclear. In both cases, SCC differentiation has been demonstrated upon disease progression, and for Case 1 was indicative of TKI resistance. In similar cases, development of SCC differentiation has in some cases been described alongside acquisition of known resistance mechanisms to first or second generation EGFR-TKIs given at the time of re-biopsy (eg., T790M, PIK3CA).3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar Likewise one of the ALK-translocated cases was noted to have MET amplification at re-biopsy.10Ueda S. Shukuya T. Hayashi T. et al.Transformation from adenocarcinoma to squamous cell lung carcinoma with MET amplification after lorlatinib resistance: a case report.Thorac Cancer. 2021; 12: 715-719Crossref PubMed Scopus (5) Google Scholar Whether development of SCC differentiation is a resistance mechanism particular to patients with oncogene-addicted NSCLC following TKI exposure is unclear; however, we are only aware of two reported cases with wild-type for EGFR and ALK mutations.3Chen Y. Tang W.Y. Tong X. Ji H. Pathological transition as the arising mechanism for drug resistance in lung cancer.Cancer Commun (Lond). 2019; 39: 53Crossref PubMed Scopus (17) Google Scholar Hence, there may be several potential explanations for apparent development of SCC histology in both cases: (1) the cases were both ADSC initially (with failure to detect SCC component in Case 1 due to sampling bias) and subsequent TKI therapy led to clonal selection of the resistant SCC component; (2) true AST occurred (e.g., Case 1) through acquisition of additional resistance mechanisms; (3) both cases were true ADSC with random sampling of ADC and/or SCC components at different time points and apparent squamous transformation unrelated to the development of resistance. Whilst in both cases described above SCC differentiation was noted on tissue biopsy, it is noteworthy that there is growing momentum for a ‘plasma-first’ approach to re-biopsy of patients during the course of metastatic NSCLC to guide therapeutic decision making. Although there may be advantages to liquid biopsies with respect to accessibility and safety, the described cases illustrate the importance of tissue biopsy to aid morphological pathological assessment to identify resistance mechanisms, such as transition to SCC or small cell carcinoma.12Clery E. Pisapia P. Feliciano S. et al.There is still a role for cytology in the 'liquid biopsy' era. A lesson from a TKI-treated patient showing adenocarcinoma to squamous cell carcinoma transition during disease progression.J Clin Pathol. 2017; 70: 798-802Crossref PubMed Scopus (15) Google Scholar At this stage, given the paucity of reported cases, it is unclear whether subsequent management should account for histological transformation to SCC; however, identification of subsequent small cell histological transformation enables use of platinum/etoposide chemotherapy and informs prognostication. Additional challenges, especially for cases of ADSC (illustrated by Case 2), include sampling bias where a single site of tissue biopsy may fail to capture both the SCC and ADC components within a patient’s tumour. In the case of an ADC component not being appreciated, this is further problematic given testing for oncogenic driver mutations does not occur routinely for cases of metastatic SCC. As such, clinician suspicion in the event of an apparent new diagnosis of SCC in a never-smoker is important to raise the question as to whether the patient may instead have ADSC and hence warrant mutation testing. SK has served on advisory boards: AZ, Pfizer, Roche, BMS, MSD, Taketa; honorarium to institution: MSD, BMS, Roche, AZ, Pfizer, Boeringher; travel support: BMS, Roche, AZ, Boeringher. JL has served on advisory board: Sanofi; honararium: Novartis, BMS, MSD; travel support: BMS, BioRad. WC has served on advisory boards for AZ, Amgen and Takeda without reimbursement. There are no other conflicts of interest to disclose.

Approximately 10% of patients with metastatic EGFR-mutant NSCLC exhibit de novo resistance to 1st generation tyrosine kinase inhibitors (TKIs). Apart from the upfront presence of resistance mutations such as T790M, there are no established predictive biomarkers for poor response to TKIs. It has been observed that high tumour PD-L1 expression is associated with poor response to EGFR TKIs in some but not all retrospective series. This study sought to determine the relationship between patients' outcome treated with 1st line EGFR TKI, and baseline PD-L1 tumour proportional score (TPS) in a large multicentre retrospective series of patients with EGFR-mutant lung cancer.

A small proportion of lung adenocarcinomas harbour ROS1 gene arrangements and are sensitive to ROS1 tyrosine kinase inhibitors. In Australia, ROS1 immunohistochemistry (IHC) is used to screen for ROS1 rearrangements in lung adenocarcinomas followed by confirmatory molecular testing such as fluorescence in situ hybridisation (FISH), if other genetic driver alterations are negative. The optimal threshold for determining ROS1 IHC positivity is not well defined, and this study aims to determine the best threshold for ROS1 IHC screening to identify all ROS1 rearranged lung adenocarcinomas.

In mNSCLC, PD-L1 expression is a biomarker for survival benefit with immune checkpoint inhibitor-based regimens (ICI). However, there are conflicting reports for its predictive value for chemotherapy alone which remains a treatment backbone in mNSCLC. We performed a meta-analysis to determine the role of PD-L1 expression in predicting response with platinum doublet chemotherapy. We performed an electronic search to identify any first-line randomized trials that compared ICI, either as monotherapy or chemoimmunotherapy, against platinum-doublet chemotherapy. We extracted only data from the control chemotherapy arm. We performed pairwise comparisons of objective response rate (ORR) and 12-month progression-free survival rate (PFS12) according to PD-L1 expression. Data was pooled across trials using the inverse variance approach. Twelve trials were identified, involving 4031 patients with EGFR/ALK wild type tumors. The majority were males (N=2710, 67%), current/ex-smoker (N=3476, 86%), performance status 1 (N=2382, 59%), and had non-squamous histology (N=2712, 67%). Chemotherapy consisted of a cisplatin/carboplatin backbone with pemetrexed/gemcitabine/nab-paclitaxel. One trial included bevacizumab (N=400, 10%). PD-L1 expression status was available in 3717 (92%) patients of which 970 (26%) were PD-L1 negative (<1%), 1513 (41%) were PD-L1 low (1-49%), and 1234 (33%) were PDL1 high (≥50%). In pairwise comparisons, ORRs for PD-L1 high and low were 33.8% and 30.4% (risk difference [RD]=5%, P=0.01), PD-L1 high and negative were 35.6% and 32.0% (RD=7%, P=0.01), and PD-L1 low and negative were 34.5% and 32.0% (RD=4%, P=0.13), respectively. PFS12 rate was not significantly different across different PD-L1 subgroups. High PD-L1 expression is associated with improved ORR with platinum doublet chemotherapy in mNSCLC. Our data suggests that this patient population is distinct, and high responses might reflect an adaptive tumor response to host immune pressure during chemotherapy. Further research is required to improve outcomes for low/negative PD-L1 tumors.

Background: Malakoplakia is a rare inflammatory response to Gram-negative bacteria, involving intracellular deposition of iron and calcium. It is associated with immunosuppression, and occurs most often in the bladder. Although rare, the colon is the most common extra-genitourinary site. Aims and methods: To identify cases of colonic malakoplakia, the Royal Prince Alfred Hospital histopathology data base was searched from 2009. A literature review was performed using PubMed with the term 'malakoplakia'. Formalin-fixed paraffin-embedded slides were stained with haematoxylin and eosin, PAS and von Kossa. Results and conclusions: A 10-year case file review identified four cases of colonic malakoplakia. Ages ranged from 50–79 with 2 males and 2 females. Clinical presentation and endoscopic appearances varied widely with an incidental polyp, mucosal changes mimicking inflammatory bowel disease, and a pelvic mass lesion with overlying normal mucosa seen. In all cases the biopsies revealed numerous histiocytes and chacteristic Michaelis-Gutmann bodies highlighted with PAS and von Kossa stains diagnostic of malakoplakia. A literature review identified 31 published case reports in adults and 10 in children of colonic malakoplakia. These cases highlight the protean manifestations of colonic malakoplakia. Consideration should be given to the diagnosis in histiocytic infiltrates in the large bowel to facilitate appropriate clinical management.