A micropapillary pattern is predictive of a poor prognosis in lung adenocarcinoma, and reduced surfactant apoprotein A expression in the micropapillary pattern is an excellent indicator of a poor prognosis

The impact of postoperative adjuvant therapy on EGFR-mutated stage IA lung adenocarcinoma with micropapillary pathological subtypes

BACKGROUND

Micropapillary (MPP) adenocarcinoma is considered one of the most aggressive pathological types of lung adenocarcinoma (LADC). This retrospective study aimed to evaluate the prognostic significance and benefit of postoperative adjuvant therapy (PAT) in stage IA LADC patients with different proportions of MPP components.

MATERIALS AND METHODS

We retrospectively examined clinical stage IA LADC patients who underwent surgical resection between August 2012 and December 2019. In terms of the proportion of MPP components (TPM), the tumors were reclassified into three categories: MPP patterns absent (TPMN); low proportions of MPP components (TPML); and high proportions of MPP components (TPMH). The dates of recurrence and metastasis were identified based on physical examinations and were confirmed by histopathological examination.

RESULTS

Overall, 505 (TPMN, n = 375; TPML, n = 92; TPMH, n = 38) patients harboring EGFR mutations were enrolled in the study. Male sex (P = 0.044), high pathological stage (P < 0.001), and MPP pathological subtype (P < 0.001) were more frequent in the TPM-positive (TPMP) group than in the TPM-negative (TPMN) group. Five-year disease-free survival (DFS) rates were significantly lower in the TPMP group than in the TPMN group (84.5% vs. 93.4%, P = 0.006). In addition, patients with high proportions (greater than 10%) of MPP components had worse overall survival (OS) (91.0% vs. 98.9%, P = 0.025) than those with low proportions (5%≤ TPM ≤ 10%). However, postoperative EGFR tyrosine kinase inhibitors (TKIs) or adjuvant chemotherapy (ACT) cannot improve DFS and OS between EGFR-mutated patients with different proportions of MPP components.

CONCLUSION

MPP was related to earlier recurrence and shortened survival time, even in stage IA. Further research needs a larger sample size to clarify that EGFR-mutated stage IA patients with MPP components obtain survival benefits from adjuvant therapy.

CT-Based Super-Resolution Deep Learning Models with Attention Mechanisms for Predicting Spread Through Air Spaces of Solid or Part-Solid Lung Adenocarcinoma

RATIONALE AND OBJECTIVES

Spread through air space (STAS) is a novel invasive pattern of lung adenocarcinoma (LUAD), and preoperative knowledge of STAS status is helpful in choosing an appropriate surgical approach.

MATERIALS AND METHODS

This retrospective study collected and analyzed 602 patients diagnosed with LUAD from two medical centers: center 1 was randomly partitioned into training (n = 358) and validation cohorts (n = 154) at a 7:3 ratio; and center 2 was the external test cohort (n = 90). Super resolution was performed on all images to acquire high-resolution images, which were used to train the SE-ResNet50 model, before creating an equivalent parameter ResNet50 model. Disparities were compared between the two models using receiver operating characteristic curves, area under the curve, accuracy, precision, sensitivity, and specificity.

RESULTS

In this study, 512 and 90 patients with LUAD were enrolled from centers 1 and 2, respectively. The curve values of the SE-ResNet50 and ResNet50 models were compared for training, validation, and test cohorts, resulting in values of 0.933 vs 0.909, 0.783 vs 0.728, and 0.806 vs 0.695, respectively. In the external test cohort, the accuracy of the SE-ResNet50 model demonstrated a 10% improvement over the ResNet50 model (82.2% vs 72.2%).

CONCLUSION

The SE-ResNet50 model based on computed tomography super-resolution has great potential for predicting STAS status in patients with solid or partially solid LUAD, with superior predictive performance compared to traditional deep learning models.

Prognostic significance and survival benefits of postoperative adjuvant chemotherapy in patients with stage IA lung adenocarcinoma with non-predominant micropapillary components

BACKGROUND

The prognostic significance of adjuvant chemotherapy (ACT) for patients with stage IA micropapillary non-predominant (MPNP) lung adenocarcinoma (LUAD) remains unknown. This study aimed to investigate the effects of postoperative ACT in patients with stage IA MPNP-LUAD.

METHODS

A total of 149 patients with pathological stage IA MPNP-LUAD who underwent surgery at our center were retrospectively analyzed. Propensity score matching (PSM) analysis was conducted to reduce potential selection bias. Kaplan-Meier analyses were used to assess the impact of ACT on recurrence-free survival (RFS), overall survival (OS), and disease-specific survival (DSS). Subgroup analyses were performed for the survival outcomes based on the percentage of micropapillary components. Cox proportional hazards regression analyses were applied to identify risk factors associated with survival.

RESULTS

The receipt or non-receipt of postoperative ACT had no significant effect on RFS, OS, and DSS among all enrolled patients with stage IA MPNP-LUAD (P > 0.05). For patients with a micropapillary component > 5%, the 5-year rates of RFS, OS, and DSS were significantly higher in the ACT group compared to the observation group, both before and after PSM (P < 0.05). However, the differences between the two groups were not significant for patients with a micropapillary component ≤ 5% (P > 0.05). The resection range (HR = 0.071; 95% CI: 0.020-0.251; P < 0.001), tumor size (HR = 2.929; 95% CI: 1.171-7.330; P = 0.022), and ACT (HR = 0.122; 95% CI: 0.037-0.403; P = 0.001) were identified as independent prognostic factors for RFS through Cox regression analysis.

CONCLUSION

Patients with stage IA MPNP-LUAD who have a micropapillary component greater than 5% might benefit from postoperative ACT, while those with a micropapillary component ≤ 5% did not appear to derive the same benefit from postoperative ACT.

Glucose Deprivation Promotes Pseudohypoxia and Dedifferentiation in Lung Adenocarcinoma

Increased utilization of glucose is a hallmark of cancer. Sodium-glucose transporter 2 (SGLT2) is a critical player in glucose uptake in early-stage and well-differentiated lung adenocarcinoma (LUAD). SGLT2 inhibitors, which are FDA approved for diabetes, heart failure, and kidney disease, have been shown to significantly delay LUAD development and prolong survival in murine models and in retrospective studies in diabetic patients, suggesting that they may be repurposed for lung cancer. Despite the antitumor effects of SGLT2 inhibition, tumors eventually escape treatment. Here, we studied the mechanisms of resistance to glucose metabolism-targeting treatments. Glucose restriction in LUAD and other tumors induced cancer cell dedifferentiation, leading to a more aggressive phenotype. Glucose deprivation caused a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. The dedifferentiated phenotype depended on unbalanced EZH2 activity that suppressed prolyl-hydroxylase PHD3 and increased expression of hypoxia-inducible factor 1α (HIF1α), triggering epithelial-to-mesenchymal transition. Finally, a HIF1α-dependent transcriptional signature of genes upregulated by low glucose correlated with prognosis in human LUAD. Overall, this study furthers current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying targets to prevent the development of resistance to therapies targeting glucose metabolism.

SIGNIFICANCE

Epigenetic adaptation allows cancer cells to overcome the tumor-suppressive effects of glucose restriction by inducing dedifferentiation and an aggressive phenotype, which could help design better metabolic treatments.

Metastatic spread of primary lung adenocarcinoma to the small intestine: A case report

INTRODUCTION AND IMPORTANCE

Metastasis of primary lung cancer to the small intestine is rare, and the prognosis is poor. Early diagnosis of small intestinal metastasis is difficult because the incidence of clinically obvious symptoms is low.

CASE PRESENTATION

This report described a rare case of small intestine metastasis of lung adenocarcinoma. It is worth noting that the patient was diagnosed with lung adenocarcinoma (T2aN0M0, stage IB) over a year ago. However, he complained of fever, black stools, and abdominal pain for about a year after the surgery. Enhanced CT scans showed thickening of the intestinal wall and dilatation of the lumen in the right iliac area and adjacent pelvic cavity. Capsule endoscopy identified a space-occupying lesion with hemorrhaging in the ileum. A laparotomy was subsequently performed, and the histopathological confirmation revealed a metastatic lung adenocarcinoma and immunohistochemistry further showed positive results for TTF-1 and CK7.

CLINICAL DISCUSSION

When patients with a history of primary lung cancer experience gastrointestinal symptoms, the possibility of distant metastasis of lung cancer to the digestive tract should be considered.

CONCLUSION

Due to the rarity of primary lung cancer metastasis to the small intestine, we report the case of a 64-year-old male who presented with symptoms of gastrointestinal bleeding and was ultimately diagnosed with metastasis of primary lung cancer to the small intestine. When patients with lung cancer present with gastrointestinal symptoms, we cannot rule out the possibility of distant metastasis from primary lung cancer, although this possibility is unlikely.

Prognostic factors of resected pathological stage I lung adenocarcinoma: evaluating subtypes and PD-L1/CD155 expression

We aimed to compare the prognostic impacts of adenocarcinoma subtypes, programmed death-ligand I (PD-L1), and CD155 expression on patients with resected pathological stage (p-stage) I lung adenocarcinoma. In total, 353 patients with completely resected p-stage I lung adenocarcinomas were retrospectively reviewed. The expression levels of PD-L1 and CD155 in tumour cells from each adenocarcinoma subtype were evaluated using several clinicopathological and histological features, such as the presence of a micropapillary pattern. A total of 52 patients (14.7%) had PD-L1-positive tumours, whereas 128 patients (36.3%) had CD155-positive tumours, with a tumour proportion score of 5% for both PD-L1 and CD155 expression. Compared with patients with other adenocarcinoma subtypes, those with solid-predominant adenocarcinomas were significantly more positive for PD-L1 and CD155. Multivariate analysis showed that PD-L1 expression status was significantly associated with progression-free survival and overall survival, whereas CD155 expression and the presence of a micropapillary pattern were not significantly associated with either parameter. Patients with PD-L1-positive tumours had poorer prognoses than those with CD155-positive tumours. Moreover, PD-L1 and CD155 were significantly expressed in solid-predominant adenocarcinomas. The results of this study suggest that immune checkpoint inhibitors can be used as adjuvants in the treatment of patients with p-stage I adenocarcinoma.

Stromal micropapillary pattern and CD44s expression predict worse outcome in lung adenocarcinomas with micropapillary pattern

OBJECTIVES

This study aims to investigate the clinicopathologic characteristics of lung adenocarcinoma with micropapillary pattern (MPP) and the expression of CD44s and CD44v6 in MPP.

METHODS

A total of 202 patients diagnosed with primary lung adenocarcinoma with MPP were included. We estimated the proportion of MPP in each tumor tissue and divided MPP into aerogenous micropapillary pattern (AMP) and stromal micropapillary pattern (SMP). The expression of CD44s and CD44v6 was estimated by immunohistochemical staining. Clinicopathologic data were collected from the patients' medical records. We also collected patients' follow-up data and used PFS (progression-free survival) as a survival indicator.

RESULTS

Lung adenocarcinoma with MPP had a high risk of pleural invasion, lymph node metastasis, in advanced TNM stage, and a high rate of EGFR mutation. The presence of SMP indicated a higher rate of pleural invasion, lymphovascular invasion, lymph node metastasis, and a worse PFS compared with pure AMP. We found high expression of CD44s in micropapillary, especially in AMP, while the absence of CD44s expression indicated shorter survival, which was an independent unfavorable factor for PFS.

CONCLUSIONS

Lung adenocarcinoma with micropapillary pattern indicated an unfavorable prognosis, which had two different pattens, AMP and SMP. SMP indicated a worse survival than AMP, and was an independent unfavorable factor for PFS. So, AMP/SMP subclassification is necessary to evaluate patient's prognosis. Furthermore, the absent expression of CD44s in micropapillary indicated shorter survival, especially in patients with EGFR mutation. Herein, CD44s may be a biological marker for micropapillary lung adenocarcinoma.

PTEN Loss Expands the Histopathologic Diversity and Lineage Plasticity of Lung Cancers Initiated by Rb1/Trp53 Deletion

INTRODUCTION

High-grade neuroendocrine tumors of the lung such as SCLC are recalcitrant cancers for which more effective systemic therapies are needed. Despite their histopathologic and molecular heterogeneity, they are generally treated as a single disease entity with similar chemotherapy regimens. Whereas marked clinical responses can be observed, they are short-lived. Inter- and intratumoral heterogeneity is considered a confounding factor in these unsatisfactory clinical outcomes, yet the origin of this heterogeneity and its impact on therapeutic responses is not well understood.

METHODS

New genetically engineered mouse models are used to test the effects of PTEN loss on the development of lung tumors initiated by Rb1 and Trp53 tumor suppressor gene deletion.

RESULTS

Complete PTEN loss drives more rapid tumor development with a greater diversity of tumor histopathology ranging from adenocarcinoma to SCLC. PTEN loss also drives transcriptional heterogeneity as marked lineage plasticity is observed within histopathologic subtypes. Spatial profiling indicates transcriptional heterogeneity exists both within and among tumor foci with transcriptional patterns correlating with spatial position, implying that the growth environment influences gene expression.

CONCLUSIONS

These results identify PTEN loss as a clinically relevant genetic alteration driving the molecular and histopathologic heterogeneity of neuroendocrine lung tumors initiated by Rb1/Trp53 mutations.

Glucose deprivation promotes pseudo-hypoxia and de-differentiation in lung adenocarcinoma

Increased utilization of glucose is a hallmark of cancer. Several studies are investigating the efficacy of glucose restriction by glucose transporter blockade or glycolysis inhibition. However, the adaptations of cancer cells to glucose restriction are unknown. Here, we report the discovery that glucose restriction in lung adenocarcinoma (LUAD) induces cancer cell de-differentiation, leading to a more aggressive phenotype. Glucose deprivation causes a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. We further show that this de-differentiated phenotype depends on unbalanced EZH2 activity, causing inhibition of prolyl-hydroxylase PHD3 and increased expression of hypoxia inducible factor 1α (HIF1α), triggering epithelial to mesenchymal transition. Finally, we identified an HIF1α-dependent transcriptional signature with prognostic significance in human LUAD. Our studies further current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying novel targets to prevent the development of resistance to therapies targeting glucose metabolism.

[A Review on Pathological High-risk Factors and Postoperative Adjuvant Chemotherapy in Stage IA Lung Adenocarcinoma]

The survival rate needs to be improved in early stage non-small cell lung cancer patients. The risk of recurrence is relatively high in invasive adenocarcinoma patients with a solid or micropapillary component, lymphovascular invasion or tumor spread through air spaces. Systemic treatment options including radical surgical resection should be explored for this population. Adjuvant chemotherapy is not recommended for patients in stage IA in current guidelines. This article is a review on the research progress of the above pathological high-risk factors and the role of adjuvant chemotherapy in patients with pathological high-risk factors in stage IA lung adenocarcinoma.
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Identification of Filigree Pattern Increases Diagnostic Accuracy of Micropapillary Pattern on Frozen Section for Lung Adenocarcinoma

INTRODUCTION

The presence of micropapillary (MIP) in early-stage lung adenocarcinoma was associated with a poorer prognosis, especially in patients undergoing sublobectomy. However, data on the sensitivity of frozen section (FS) evaluation of MIP was still limited. We included the concept of filigree pattern on FS to assess its effect on the diagnostic sensitivity and specificity of MIP, and verify its prognostic value in stage T1 lung adenocarcinoma.

METHODS

A panel of five pathologists evaluated 125 patients with T1 lung adenocarcinoma from January to February 2014 as a study cohort, and 151 patients from January to February 2020 as a validation cohort. The diagnostic accuracy of filigree and classical micropapillary (cMIP) pattern on FS was investigated.

RESULTS

Diagnostic sensitivity of MIP pattern on FS increased from 43.2% to 65.3% and 56.8% to 81.1% in the study cohort and validation cohort, and both with good specificity. Filigree not only increased the sensitivity of identifying MIP when absence of cMIP, but also increased the sensitivity when presence of minor amount of cMIP. The almost perfect agreement among five pathologists was reached on cMIP and substantial agreement was reached on the filigree in the two cohorts. Moreover, the cMIP and filigree were both correlated with poorer recurrence-free survival (p_cMIP = 0.003; p_filigree = 0.032) and overall survival (p_cMIP = 0.004; p_filigree = 0.005).

CONCLUSION

Identification of filigree may improve the diagnostic sensitivity of MIP pattern on FS. FS was feasible for the detection of filigree and cMIP patterns in stage T1 lung adenocarcinomas.

YBX1 Enhances Metastasis and Stemness by Transcriptionally Regulating MUC1 in Lung Adenocarcinoma

Abnormal expression of the transcription factor Y-box-binding protein-1 (YBX1) is associated with the proliferation, migration, aggressiveness, and stem-like properties of various cancers. These characteristics contribute to the tumorigenesis and metastasis of cancer. We found that the expression levels of Mucin-1 (MUC1) and YBX1 were positively correlated in lung adenocarcinoma cells and lung adenocarcinoma tissue. Our retrospective cohort study of 176 lung adenocarcinoma patients after surgery showed that low expression of both YBX1 and MUC1 was an independent predictor of the prognosis and recurrence of lung adenocarcinoma. In lung adenocarcinoma cells, the silencing/overexpression of YBX1 caused a simultaneous change in MUC1, and MUC1 overexpression partially reversed the decreased tumor cell migration, aggressiveness, and stemness caused by YBX1 silencing. Moreover, chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays proved that MUC1 was the downstream target of YBX1 and that YBX1 bound to the -1480~-1476 position in the promoter region of MUC1 to regulate its transcription. Furthermore, in mouse xenograft models and a lung cancer metastasis model, MUC1, which is downstream of YBX1, partially reversed the decreased number and size of tumors caused by YBX1 silencing. In conclusion, our findings indicated a novel mechanism by which YBX1 promotes the stemness and metastasis of lung adenocarcinoma by targeting MUC1 and provided a combination approach for diagnosis different from traditional single tumor biomarkers to predict patient prognosis and provide clinical treatment targets.

A case of nonmucinous pulmonary micropapillary adenocarcinoma mimicking pulmonary tuberculosis

We report a rare case of nonmucinous pulmonary micropapillary adenocarcinoma mimicking pulmonary tuberculosis. A 68-year-old woman was hospitalized with hemoptysis. Her computed tomography revealed cavities and tree-in-bud appearance similar to the extensive form of pulmonary tuberculosis. However, histopathological findings of transbronchial biopsies of all lesions revealed adenocarcinoma and no pulmonary tuberculosis. Tree-in-bud appearance may relate to the floating micropapillary tufts in alveolar spaces. If pulmonary carcinoma is complicated by pulmonary tuberculosis, patients must be isolated and disadvantaged in cancer treatments. Therefore, recognizing this case may be therapeutically useful for respiratory physicians treating both diseases.

Cancer Antigen 15-3 Serum Level as a Biomarker for Advanced Micropapillary Urothelial Carcinoma of the Bladder: A Case Report

A 73-year-old woman with no history of disease was referred to our hospital with fatigue and joint pain. Screening blood test showed that her cancer antigen 15-3 (CA 15-3) serum level was elevated to 36.6 U/mL, and a contrast-enhanced computed tomography scan revealed a bladder tumor without metastasis. Cystoscopy showed a papillary and a small kissing tumor, and the histopathological analysis of the bladder tumor obtained by transurethral resection (TUR) showed invasive urothelial carcinoma (UC) with micropapillary variant (pT1). At 4 weeks after TUR, the CA 15-3 serum level was markedly increased to 180.6 U/mL, and radiographic examinations revealed multiple regional and nonregional lymph node metastases. The patient received systemic therapy with gemcitabine and cisplatin. After 3 cycles of chemotherapy, the size of all lymph node metastases reduced by 80% in diameter, and the CA 15-3 serum level decreased from 238.2 to 11.4 U/mL. Immunohistological analysis showed that the bladder tumor was positive for mucin 1, of which CA 15-3 is an epitope. In our patient, changes in the CA 15-3 serum levels were in congruence with the clinical course of advanced micropapillary UC (MPUC). Therefore, the CA 15-3 serum level may be a potentially valuable biomarker for MPUC.

A systematic dissection of the epigenomic heterogeneity of lung adenocarcinoma reveals two different subclasses with distinct prognosis and core regulatory networks

BACKGROUND

Lung adenocarcinoma (LUAD) is a highly malignant and heterogeneous tumor that involves various oncogenic genetic alterations. Epigenetic processes play important roles in lung cancer development. However, the variation in enhancer and super-enhancer landscapes of LUAD patients remains largely unknown. To provide an in-depth understanding of the epigenomic heterogeneity of LUAD, we investigate the H3K27ac histone modification profiles of tumors and adjacent normal lung tissues from 42 LUAD patients and explore the role of epigenetic alterations in LUAD progression.

RESULTS

A high intertumoral epigenetic heterogeneity is observed across the LUAD H3K27ac profiles. We quantitatively model the intertumoral variability of H3K27ac levels at proximal gene promoters and distal enhancers and propose a new epigenetic classification of LUAD patients. Our classification defines two LUAD subgroups which are highly related to histological subtypes. Group II patients have significantly worse prognosis than group I, which is further confirmed in the public TCGA-LUAD cohort. Differential RNA-seq analysis between group I and group II groups reveals that those genes upregulated in group II group tend to promote cell proliferation and induce cell de-differentiation. We construct the gene co-expression networks and identify group-specific core regulators. Most of these core regulators are linked with group-specific regulatory elements, such as super-enhancers. We further show that CLU is regulated by 3 group I-specific core regulators and works as a novel tumor suppressor in LUAD.

CONCLUSIONS

Our study systematically characterizes the epigenetic alterations during LUAD progression and provides a new classification model that is helpful for predicting patient prognosis.

Is There a Role for Percutaneous Ablation for Early Stage Lung Cancer? What Is the Evidence?

PURPOSE OF REVIEW

For patients with early stage non-small-cell lung cancer (NSCLC), thermal ablation (TA) has become in the least two decades an option of treatment used worldwide for patients with comorbidities who are not surgical candidates. Here, we review data published with different TA techniques: radiofrequency ablation (RFA), microwave ablation (MWA) and cryoablation. This paper reviews also the comparison that has been made between TA and stereotactic radiotherapy (SBRT).

RECENT FINDINGS

A majority of retrospective studies, the absence of comparative studies, and the variety of techniques make difficult to get evident data. Nevertheless, these stand-alone techniques have demonstrated local efficacy for tumors less than 3 cm and good tolerance on fragile patients. Many recent reviews and database analyses show that outcomes after TA (mainly RFA and MWA) are comparable to SBRT in terms of survival rates. For patients who are unfit for surgery, TA has demonstrated interesting results for safety, benefits in overall survival, and acceptable local control.

Correlation between spread through air spaces (STAS) and other clinicopathological parameters in lung cancer

BACKGROUND

"Spread through airspace" (STAS) is defined as micropapillary clusters, solid nests or single cells of tumor extending beyond the edge of the tumor into the air spaces of the surrounding lung parenchyma. It is associated with reduced overall survival and disease-free survival. Assessment of STAS in lung cancer appears to be necessary to guide clinical interventions. However, data on the correlation between the status of STAS and other lung cancer clinicopathological parameters are scarce.

METHODS

We reviewed 240 resected lung cancers and investigated the clinical significance of STAS in relation to other relevant lung cancer clinicopathological variables. We performed univariate and multivariate logistic regression analyses with STAS as a dependent variable.

RESULTS

Of the total 240 patients, STAS was observed in 67 (27.9 %) of them. STAS is highly prevalent in adenocarcinoma with a micropapillary growth pattern (70.0 %) than in other lung cancer growth patterns. STAS was frequently reported in wedge resections (31.0%) than in lobectomy specimens (26.7 %). STAS was significantly associated with advanced pN stage (p < 0.001) and lymphovascular invasion (p = 0.005). In multivariate models, we found that lung cancers in the right lower lobe (RLL) (OR, 2.674; 95 % CI = 1.313-5.448, p = 0.007), micropapillary lung cancer growth pattern (OR = 5.199, 95 % CI = 1.220-22.162, p = 0.026), and pN2 stage (OR = 3.683, 95 % CI = 1.324-10.245, p = 0.013) serve as independent predictors for STAS.

CONCLUSION

Our findings suggest that the presence of STAS is associated with right lower lobe tumors, micropapillary adenocarcinoma, and pN2 tumor stage. Hence, it could serve as one of the prognostically significant histologic findings in lung cancer. It is thus valid to mandate reporting STAS status in CAP surgical pathology lung cancer case summaries.

Increased VEGF-A in solid type of lung adenocarcinoma reduces the patients' survival

The histological classification of lung adenocarcinoma includes 5 types: lepidic, acinar, papillary, micropapillary and solid. The complex gene interactions and anticancer immune response of these types are not well known. The aim of this study was to reveal the survival rates, genetic alterations and immune activities of the five histological types and provide treatment strategies. This study reviewed the histological findings of 517 patients with lung adenocarcinoma from The Cancer Genome Atlas (TCGA) database and classified them into five types. We performed gene set enrichment analysis (GSEA) and survival analysis according to the different types. We found six oncogenic gene sets that were higher in lung adenocarcinoma than in normal tissues. In the survival analysis of each type, the acinar type had a favorable prognosis, and the solid subtype had an unfavorable prognosis; however, the survival differences between the other types were not significant. Our study focused on the solid type, which had the poorest prognosis. The solid type was related to adaptive immune resistance associated with elevated CD8 T cells and high CD274 (encoding PD-L1) expression. In the pathway analyses, the solid type was significantly related to high vascular endothelial growth factor (VEGF)-A expression, reflecting tumor angiogenesis. Non-necrosis/low immune response affected by high VEGF-A was associated with worse prognosis. The solid type associated with high VEGF-A expression may contribute to the development of therapeutic strategies for lung adenocarcinoma.

Novel imprint cytological classification is correlated with tumor spread through air spaces in lung adenocarcinoma

OBJECTIVES

Spread through air spaces (STAS) is a risk factor for local recurrence after sublobar resection in lung cancer patients. We recently proposed the novel Nakayama-Higashiyama imprint cytological classification (N-H classification) based on small-sized lung adenocarcinoma surgical specimens, which correlated with histological patterns and nodal involvement. This study aimed to evaluate the correlation between STAS and the N-H classification and to validate the N-H classification as an intraoperative predictor of the presence of STAS.

MATERIALS AND METHODS

We retrospectively analyzed 164 intraoperative imprint cytologies and their paired histologic specimens from patients undergoing surgical resection for lung adenocarcinoma in our institute in 2017-2019. Using the NH classification, imprint cytological findings were classified into 5 groups (Groups I to V) based on cell cluster shape, cell and nucleus size, and the existence of necrosis. We examined the characteristics of imprint cytology and STAS in the resected tissues and analyzed the relationship between them.

RESULTS

Tumor STAS was observed in 29 (17.7 %) cases. The presence of STAS was significantly associated with the NH classification (P < 0.0001). STAS was present in 6 of 57 cases (10.5 %) in NH classification Group II, 11 of 42 cases (26.2 %) in Group III, and 12 of 28 cases (42.9 %) in Group IV/V; STAS was not observed in any case in Group I. Logistic regression analysis revealed that tumors with a ground glass opacity rate of <50 % on computed tomography (P = 0.00867) and Groups III-V of the NH classification (P = 0.00201) were significant independent predictors for STAS.

CONCLUSION

Intraoperative imprint cytology with the N-H classification for lung adenocarcinoma is well correlated with the STAS status of the tumor and might have applications as an intraoperative predictive marker of STAS. This classification may be useful for intraoperative detection of STAS and in the decision-making process for the surgical procedure.

Large nest micropapillary pattern of lung adenocarcinoma has poorer prognosis than typical floret pattern: analysis of 1,062 resected tumors

Background

A micropapillary pattern (MP-p) is related to poor prognosis in patients with lung adenocarcinoma (L-ADC). In 2015, the WHO defined the MP-p as "papillary tufts forming florets that lack fibrovascular cores and may appear detached from alveolar walls"; however, the sizes of tumor clusters in air space were not mentioned in this classification.

Methods

We evaluated the MP-p dividing the cluster sizes in the air space by reviewing 1,062 cases of resected L-ADCs. We classified MP-p into two types according to cluster size as follows: typical floret MP-p, tumors with small-to-medium-sized clusters (1-20 tumor cells); and large nest MP-p, tumors with large-sized clusters (>20 tumor cells, large nest). We then recorded the frequency of each type and investigated the association between the MP-p type and clinicopathological factors.

Results

Twenty-nine percent of L-ADCs (n=308) were MP-p-positive. Typical floret MP-p and large nest MP-p were observed in 244 tumors (22.9%) and 64 tumors (6.0%), respectively. Only 7 additional micropapillary ADCs were detected when we reclassified ADCs in addition to large nest MP-p. Tumors with large nest MP-p showed the highest frequency of node metastasis and worse prognosis compared to those with typical floret MP-p and absent (P<0.001). In multivariate analysis, patients with L-ADC with typical floret MP-p and large nest MP-p showed a higher recurrence rate [hazard ratio (HR): 1.762 (type 1 vs. absent), HR: 2.450 (type 2 vs. absent)].

Conclusions

Large nest MP-p should be included in the original MP-p and recorded separately.

Heterogeneous components of lung adenocarcinomas confer distinct EGFR mutation and PD-L1 expression

Background

Lung adenocarcinoma (LAC) is composed of lepidic, papillary, mucinous, micropapillary and solid components in its parenchyma. Complex responses to therapeutics result from intratumoral heterogeneity. However, it remains confused that what components in a mixed LAC tumor are responsible to the heterogeneous EGFR mutation and PD-L1 expression.

Methods

We investigated EGFR status via laser microdissection to capture spatially separated cancer cell subpopulations and digital droplet PCR to determine the abundance of EGFR sensitizing mutation and naïve T790M. Whilst, PD-L1 expression level via tumor proportion score (TPS) was evaluated by Ventana immunohistochemistry using SP263 antibody. PD-L1 expression levels were tiered in < 1, 1–49% and > =50% groups.

Results

EGFR mutation harbored in 154 (59%) of 261 LAC patients and more frequently occurred in papillary, lepidic and micropapillary constituents. Higher levels of PD-L1 were found in LACs at stage III and IV (68.3%) versus those at stage I and II (31.7%) (P = 0.04). Solid predominant LACs (41.3%) expressed PD-L1 with TPS > =50%, versus mucinous and lepidic LACs (P < 0.01). LACs with solid constituents also had more positive proportion of PD-L1 protein. Cut-offs < 1, 1–49% or > =50% were associated with patients’ progression-free survival and longer in the < 1% group (22.9 month, 95% CI 17.6–28.2) (P < 0.05). LACs consisting of two constituents with PD-L1 TPS < 1% had a better prognosis than the groups with single component and more than two components (P < 0.05). Eighteen LACs (6.9%) had concomitantly deletion in exon 19 or L858R and naïve T790M mutation. The abundance of T790M varied diversely with sensitizing mutation. PD-L1 expression was not concordant in same components and usually negative in the EGFR-mutated constituents. Heterogeneous PD-L1 expression occurred in the vicinity of stromal tissues. 58.8, 29.4 and 11.8% in ALK positive LACs (N = 17) were found PD-L1 expression via cutoffs of < 1, 1–49% and > =50%, respectively (P > 0.05).

Conclusion

Intratumoral genetic heterogeneity of LACs was demonstrated associated with histological patterns. Heterogeneous PD-L1 expression in higher level usually occurred in solid component both in EGFR mutated and EGFR wild-typed LACs. EGFR mutated LACs heterogeneously had sensitizing and resistant mutation and was accompanied with PD-L1 expression, but discordant among histological constituents. Immune checkpoint inhibitor combined with third generation EGFR tyrosine kinase inhibitor should be more effective to these LACs.

Micropapillary pattern is associated with the development of brain metastases and the reduction of survival time in EGFR-mutation lung adenocarcinoma patients with surgery

OBJECTIVE

The role of micropapillary pattern (MIP) in EGFR-mutated NSCLC patients with brain metastases (BM) after complete surgical resection still remains unclear. Therefore, a retrospective study was conducted to evaluate the role of MIP in those patients.

METHODS

This study included 332 stage I-III patients with EGFR-mutant lung adenocarcinoma and complete resection. Patients were classified in four groups: the MIP-positive patients without BM development, the MIP-negative patients without BM development, the MIP-positive patients with BM development and the MIP-negative patients with BM development. Intracranial disease-free survival (iDFS), systemic disease-free survival (DFS) and overall survival (OS) were evaluated.

RESULTS

The median OS in the whole group was 70 months. The patients with MIP show inferior DFS (13 months vs. 22 months; P < 0.001) and OS (56 months vs. 74 months; P < 0.001). Furthermore, BM development was more likely to be found in patients with MIP (P = 0.001). In addition, the MIP-positive patients showed a significantly shorter iDFS compared with MIP-negative patients (14.5 months vs. 26 months; P < 0.001). Furthermore, the MIP-positive patients had significantly inferior iDFS in both BM as first line development groups (13 months vs. 19 months; P < 0.001) and BM as non-first line development groups (18 months vs. 33 months; P = 0.007).

CONCLUSIONS

MIP was related to the earlier recurrence and shortened survival time. In addition, MIP was an independent poor prognostic factor for the increase of BM rate and the shortened time of BM development after surgery.

Micropapillary adenocarcinoma of lung: Morphological criteria and diagnostic reproducibility among pulmonary pathologists

CONTEXT

Invasive micropapillary adenocarcinoma (MPC) is an aggressive variant of lung adenocarcinoma, frequently manifesting with advanced stage lymph node metastasis and decreased survival.

OBJECTIVE

Identification of this morphology is important, as it is strongly correlated with poor prognosis regardless of the amount of MPC component. To date, no study has investigated the morphological criteria used to objectively diagnose it.

DESIGN

Herein, we selected 30 cases of potential MPC of lung, and distributed 2 digital images per case among 15 pulmonary pathology experts. Reviewers were requested to diagnostically interpret, assign the percentage of MPC component, and record the morphological features they identified. The noted features included: columnar cells, elongated slender cell nests, extensive stromal retraction, lumen formation with internal epithelial tufting, epithelial signet ring-like forms, intracytoplasmic vacuolization, multiple nests in the same alveolar space, back-to-back lacunar spaces, epithelial nest anastomosis, marked pleomorphism, peripherally oriented nuclei, randomly distributed nuclei, small/medium/large tumor nest size, fibrovascular cores, and spread through air-spaces (STAS).

RESULTS

Cluster analysis revealed three subgroups with the following diagnoses: "MPC", "combined papillary and MPC", and "others". The subgroups correlated with the reported median percentage of MPC. Intracytoplasmic vacuolization, epithelial nest anastomosis/confluence, multiple nests in the same alveolar space, and small/medium tumor nest size were the most common criteria identified in the cases diagnosed as MPC. Peripherally oriented nuclei and epithelial signet ring-like forms were frequently identified in both the "MPC" and "combined papillary and MPC" groups.

CONCLUSIONS

Our study provides objective diagnostic criteria to diagnose MPC of lung.

Classification and Pathology of Lung Cancer

Advancement in the understanding of lung tumor biology enables continued refinement of lung cancer classification, reflected in the recently introduced 2015 World Health Organization classification of lung cancer. In small biopsy or cytology specimens, special emphasis is placed on separating adenocarcinomas from the other lung cancers to effectively select tumors for targeted molecular testing. In resection specimens, adenocarcinomas are further classified based on architectural pattern to delineate tissue types of prognostic significance. Neuroendocrine tumors are divided into typical carcinoid, atypical carcinoid, small cell carcinoma, and large cell neuroendocrine carcinoma based on a combination of features, especially tumor cell proliferation rate.

Prognostic stratification model for patients with stage I non-small cell lung cancer adenocarcinoma treated with surgical resection without adjuvant therapies using metabolic features measured on F-18 FDG PET and postoperative pathologic factors

PURPOSE

In the management of non-small cell lung cancer (NSCLC), the prognostic stratification of stage I tumors without indication of adjuvant therapy, remains to be elucidated in order to better select patients who can benefit from additional therapies. We aimed to stratify the prognosis of patients with stage I NSCLC adenocarcinoma using clinicopathologic factors and F-18 FDG PET.

MATERIALS AND METHODS

We retrospectively enrolled 128 patients with stage I NSCLC without any high-risk factors, who underwent curative surgical resection without adjuvant therapies. Preoperative clinical and postoperative pathologic factors were evaluated by medical record review. Standardized uptake value corrected with lean body mass (SUL_max) was measured on F-18 FDG PET. Among the factors, independent predictors for recurrence-free survival (RFS) were selected using univariate and stepwise multivariate survival analyses. A prognostic stratification model for RFS was designed using the selected factors.

RESULTS

Tumors recurred in nineteen patients (14.8%). Among the investigated clinicopathologic and FDG PET factors, SUL_max on PET and spread through air spaces (STAS) on pathologic review were determined to be independent prognostic factors for RFS. A prognostic model was designed using these two factors in the following manner: (1) Low-risk: SUL_max ≤ 1.9 and no STAS, (2) intermediate-risk: neither low-risk nor high-risk, (3) high-risk: SUL_max>1.9 and observed STAS. This model exhibited significant predictive power for RFS.

CONCLUSION

We showed that FDG uptake and STAS are significant prognostic markers in stage I NSCLC adenocarcinoma treated with surgical resection without adjuvant therapies.

Prognostic factors in curatively resected pathological stage I lung adenocarcinoma

Background

Patients with pathological stage I (p I) lung adenocarcinoma show variabilities in prognosis even after complete resection. The factors resulting in heterogeneities of prognosis remain controversy. The aim of this study was to identify the risk factors affecting recurrence/metastasis and survival in patients with curatively resected p I lung adenocarcinoma.

Methods

A total of 252 patients with p I lung adenocarcinoma underwent curative resection between January 1st, 2009 to September 30th, 2011 were retrospectively reviewed to analyze the associations of recurrence and survival with the following clinicopathological variables: gender, age, cigarette smoking, family cancer history, tumor size, TNM stage, tumor differentiation, visceral pleural invasion, bronchial involvement, lymphovascular invasion, postoperative adjuvant treatment, pathological subtypes and micropapillary pattern.

Results

Among those 252 patients, 48 had local recurrence or distant metastasis, the rest 204 patients had no relapse until the last follow-up. Cox univariate survival analysis revealed that tumor size (P<0.001), TNM stage [disease-free survival (DFS), P<0.001; overall survival (OS), P=0.004], tumor differentiation (P<0.001), bronchial involvement (P<0.001), lymphovascular invasion (DFS, P=0.021; OS, P=0.001) and micropapillary pattern (DFS, P<0.001; OS, P=0.003) were significantly associated with DFS and OS, while cigarette smoking (P=0.029) and pathological subtypes (P=0.041) were found to be risk factors for DFS either. In multivariate analysis, tumor differentiation (P<0.001) was an independent risk factor for both DFS and OS, TNM stage (P=0.007), bronchial involvement (P=0.004) and micropapillary pattern (P=0.001) only for DFS, while tumor size (P=0.009) and lymphovascular invasion (P=0.010) were found to be independent risk factors only for OS.

Conclusions

Tumor size, TNM stage, tumor differentiation, bronchial involvement, lymphovascular invasion and micropapillary pattern could be considered as risk factors for predicting local recurrence or distant metastasis and survival in curatively resected p I lung adenocarcinoma patients.

EGFR, KRAS, and BRAF mutational profiles of female patients with micropapillary predominant invasive lung adenocarcinoma

Background/aim: This study aimed to analyze EGFR, KRAS, and BRAF mutations in females with micropapillary predominant invasive lung adenocarcinoma and their relationships with immunohistochemical and clinicopathological patterns.Materials and methods: A total of 15 females with micropapillary lung adenocarcinoma were selected. Mutational analysis of the EGFR, KRAS, and BRAF genes was carried out. Information regarding the demographic data, tumor size, treatment, and survival time for each patient was collated, and the predominant cell type, secondary architectural growth patterns, psammoma bodies, necrosis, and visceral pleural and angiolymphatic invasions were evaluated.Results: We identified EGFR mutation in six cases, KRAS mutation in three cases, and BRAF mutation in one case. EGFR, c-kit, VEGFR, and bcl-2 positivity was observed in ten, seven, four, and six cases, respectively. All cases were positive for VEGF (strong positivity in 11 cases and weak positivity in four cases) and bcl-2 (strong positivity in nine cases and weak positivity in six cases). Seven (46.6%) cases were positive for c-kit and 10 (66.6%) cases were positive for EGFR. Conclusion: EGFR mutation occurred at a higher incidence rate in micropapillary predominant invasive adenocarcinoma than has previously been found in conventional lung adenocarcinomas. KRAS mutation was observed as having a similar frequency to what was previously observed, but the frequency of BRAF mutation was lower than previously reported.

Detection of tumor spread through airspaces by airway secretion cytology from resected lung cancer specimens

It currently remains unclear whether tumor spread through airspaces (STAS) actually exist in vivo or are an artifact. The morphologies of STAS and tumor cell clusters in airway secretions collected from the segmental or lobar bronchus of resected lung adenocarcinomas and squamous cell carcinomas were compared among 48 patients. The EGFR status of tumor cell clusters in airway secretions was also compared with that of the main tumor in EGFR mutant adenocarcinomas. Tumor cell clusters were observed in the airway secretion cytology of ten patients (20.8%), and eight patients were adenocarcinoma (20.0% of adenocarcinoma). The morphology of STAS closely resembled that of tumor cell clusters detected in airway secretion cytology. The positive rates of airway secretion cytology were 83.3%, 100%, and 50% in papillary adenocarcinoma, micropapillary adenocarcinoma, and invasive mucinous adenocarcinoma, respectively. Among three EGFR mutant adenocarcinomas, the EGFR mutation subtypes of the main tumors in FFPE sections and tumor cell clusters in airway secretions were identical. These indicate that STAS may be detected in the airway secretion cytology. STAS is common in papillary or micropapillary adenocarcinoma and may spread as far as the segmental or lobar bronchus at the time of surgery.

A Clinicopathological Study of Small Lung Adenocarcinoma 1 cm or Less in Size: Emphasis on Histological Subtypes Associated With Lymph Node Metastasis and Recurrence

BACKGROUND

The aim of this study was to assess the prognostic significance of the newly proposed 2015 World Health Organization (WHO) lung adenocarcinoma classification for patients undergoing resection for small (≤1 cm) lung adenocarcinoma. We also investigated whether lobectomy offers prognostic advantage over limited resection for this category of tumors.

METHODS

A retrospective study of resected pulmonary adenocarcinomas (n = 83) in sizes 1 cm or less was carried out in which comprehensive histologic subtyping was assessed according to the 2015 WHO classification on all consecutive patients who underwent lobectomy or limited resection between 2008 and 2015. Correlation between clinicopathologic parameters and the difference in recurrence between lobectomy and limited resection group was evaluated.

RESULTS

Our data show that the proposed 2015 WHO classification identifies histological subsets of small lung adenocarcinomas with significant differences in prognosis. No recurrence was noted for patients with adenocarcinoma in situ and minimally invasive adenocarcinoma. Invasive adenocarcinomas displayed high heterogeneity and the presence of micropapillary component of 5% or greater in adenocarcinomas was significantly related to lymph node involvement and recurrence ( P < .001). Stage Ia patients who underwent limited resection had a higher risk of recurrence than did those treated by lobectomy (P < .05).

CONCLUSIONS

Application of the 2015 WHO classification identifies patients with adenocarcinoma in situ and minimally invasive adenocarcinoma had excellent prognosis. Micropapillary pattern was associated with high risk of lymph node metastasis and recurrence.

Clinicopathological Characteristics of Lung Adenocarcinoma with Unexpected Lymph Node Metastasis

PURPOSE

The objective is to demonstrate the clinicopathological characteristics of patients with unexpected node-positive lung adenocarcinoma and to analyze predictive factors of unexpected disease.

METHODS

We reviewed 225 patients with lung adenocarcinoma who underwent curative-intent operation between January 2008 and December 2014. Unexpected node-positive diseases were defined as cases with hilar or mediastinal lymph nodes metastasis in spite of both negative significant enlargement of lymph nodes on preoperative chest computed tomography (CT) and negative fluorodeoxyglucose (FDG) uptake in lymph nodes on preoperative positron emission tomography (PET)/CT. We retrospectively analyzed clinical features of these patients and evaluated associated factors for unexpected diseases.

RESULTS

There were 41 patients (18%) with unexpected node-positive disease, consisting of 16 (39%) unexpected pN1 and 25 (61%) unexpected pN2 diseases. The most common predominant subtype was papillary (22 patients; 54%), and 17 patients (41%) had micropapillary component in the tumors. Younger age (p <0.01), left side (p <0.01), larger tumor size (p <0.01), and having a micropapillary component (p <0.01) were significant associated factors of unexpected diseases in multivariate analysis.

CONCLUSION

Histological findings of the primary tumor are often important because they can provide predictive information for lymph nodes status. Having a micropapillary component was one of the significant predictors of unexpected node-positive diseases.

Prognostic significance of histologic subtype in pStage I lung adenocarcinoma

The International Association for the Study of Lung Cancer, the American Thoracic Society, and the European Respiratory Society (IASLC/ATS/ERS) proposed a new histologic classification of lung adenocarcinoma in 2011. While several studies have already validated the prognostic value of this new classification of lung adenocarcinoma, we conducted own investigation in the present study. This study included 197 patients with invasive lung adenocarcinoma who underwent complete resection. Pathologic diagnoses were made in accordance with the new IASLC/ATS/ERS classification for lung adenocarcinoma. The lepidic/acinar/papillary group had a significantly better prognosis than the micropapillary/solid/invasive mucinous adenocarcinoma group (5-year recurrence-free survival [RFS] 73 vs. 21%: p < 0.01, 5-year overall survival 85 vs. 52%: p < 0.01). Age (hazard ratio [HR], 1.898; p = 0.03), CEA (HR, 1.873; p = 0.03), pStage (HR, 6.149; p < 0.01), and histologic subtype (HR, 2.342; p = 0.01) were independent prognostic factors for the RFS. Furthermore, age (HR, 3.242; p = 0.04), CEA (HR, 3.405; p = 0.03) and histologic subtype (HR, 11.108; p < 0.01) were independent prognostic factors for the progression-free survival in pStage I. The histologic subtype correlated with the prognosis of pStage I of lung adenocarcinoma. Patients in the high-grade group of lung adenocarcinoma, which included solid, micropapillary and invasive mucinous adenocarcinoma with pStage I, should be considered candidates for postoperative adjuvant therapy.

Expression level of CRKL and AXL combined with exon 19 deletion in EGFR and ALK status confer differential prognosis of lung adenocarcinoma subtypes

Non-small cell lung cancer (NSCLC) is a lethal cancer-related disease in population. Adenocarcinoma (AC) is subclassified into several subtypes based on the new classification by the International Association for the Study of Lung Cancer, American Thoracic Society and European Respiratory Society in 2011. Correlation between original expression of Crk-like (CRKL) and anaplastic lymphoma receptor tyrosine kinase in diverse histological components of AC and epidermal growth factor receptor (EGFR) or ALK status was evaluated by immunohistochemistry and sequencing in present study. A total of 106 cases, including 83 patients (78.3%) with mixed-type ACs, were assessed in the present study using eligible follow-up data. The ACs consisted of 32 acinar, 12 papillary, 5 mucinous, 11 micropapillary and 46 solid-predominant ACs. In total, 69.8% samples were composed of 2 or 3 histological components, with different expression levels of CRKL and AXL. ACs with EGFR mutation had a higher level of AXL expression compared with ACs without mutation (P=0.019). Multivariate survival analysis showed that AC subtypes and EGFR mutation subtypes were significantly associated with the progression-free survival (PFS) time. Acinar AC was the subtype with the most notable PFS time (30.6 months), which was significantly different from the PFS time of papillary, mucinous, micropapillary and solid-predominant ACs (hazard ratio, 0.4; 95% CI, 0.21-0.75; P=0.005). Among the ACs with exon 19 mutation, the median PFS time (28.8 months) of patients with a lower level of AXL protein expression was increased compared with the PFS time of patients with the L858R mutation and wild-type EGFR (9.1 months and 11 months, respectively; P=0.03), whereas no significant difference in ACs with an increased level of AXL expression. However, AC patients with higher level of CRKL expression had better PFS (28.8 months) than patients with the L858R mutation and wild-type EGFR (9.1 months and 11.3 months, respectively). Exon 19 deletion is an important status that is associated with an improved response to conventional chemotherapy. The identification of EGFR mutations combined with CRKL and AXL status may potentially alter the way that lung AC is treated.

Histologic Subtype in Core Lung Biopsies of Early-Stage Lung Adenocarcinoma is a Prognostic Factor for Treatment Response and Failure Patterns After Stereotactic Body Radiation Therapy

PURPOSE

Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment for early-stage lung cancer. The histologic subtype of surgically resected lung adenocarcinoma is recognized as a prognostic factor, with the presence of solid or micropapillary patterns predicting poor outcomes. We describe the outcomes after SBRT for early-stage lung adenocarcinoma stratified by histologic subtype.

METHODS AND MATERIALS

We identified 119 consecutive patients (124 lesions) with stage I to IIA lung adenocarcinoma who had undergone definitive SBRT at our institution from August 2008 to August 2015 and had undergone core biopsy. Histologic subtyping was performed according to the 2015 World Health Organization classification. Of the 124 tumors, 37 (30%) were a high-risk subtype, defined as containing a component of solid and/or micropapillary pattern. The cumulative incidences of local, nodal, regional, and distant failure were compared between the high-risk and non-high-risk adenocarcinoma subtypes using Gray's test, and multivariable-adjusted hazard ratios (HRs) were estimated from propensity score-weighted Cox regression models.

RESULTS

The median follow-up for the entire cohort was 17 months and for surviving patients was 21 months. The 1-year cumulative incidence of and adjusted HR for local, nodal, regional, and distant failure in high-risk versus non-high-risk lesions was 7.3% versus 2.7% (HR 16.8; 95% confidence interval [CI] 3.5-81.4), 14.8% versus 2.6% (HR 3.8; 95% CI 0.95-15.0), 4.0% versus 1.2% (HR 20.9; 95% CI 2.3-192.3), and 22.7% versus 3.6% (HR 6.9; 95% CI 2.2-21.1), respectively. No significant difference was seen with regard to overall survival.

CONCLUSIONS

The outcomes after SBRT for early-stage adenocarcinoma of the lung correlate highly with histologic subtype, with micropapillary and solid tumors portending significantly higher rates of locoregional and metastatic progression. In this context, the histologic subtype determined from core biopsies is a prognostic factor and could have important implications for patient selection, adjuvant treatment, biopsy methods, and clinical trial design.

Micropapillary: A component more likely to harbour heterogeneous EGFR mutations in lung adenocarcinomas

The micropapillary (MP) subtype has recently been established to be a distinct marker of poor prognosis in lung adenocarcinomas (LACs). According to the 2015 WHO classification system, LAC constituents are required to be precisely reported. T790M mutation and an insertion in exon 20 (E20ins) are associated with EGFR-TKI resistance. A total of 211 LAC patients were involved in this study, and EGFR mutations were determined using an amplification refractory mutation system (ARMS). Sex, smoking history, lymph node status, and clinical stage differed significantly between the EGFR wild type and mutant groups (p < 0.05). The EGFR mutation occurred more frequently in female, non-smokers, ACs with papillary (85.7%) or MP components (91.4%) (p < 0.001). Twenty ACs with naïve T790M or E20ins were microdissected. The AC constituents metastasizing to lymph nodes exhibited a phenotype and EGFR status that was consistent with the primary loci constituents. Glomerulus-like solid components exhibited the same EGFR status as the surrounding T790M-mutated MP components. The MP and glomerulus-like portions in AC tumours exhibited a congenial EGFR status, but the acinar cells with papillary cells were heterogeneous. The naïve T790M mutants, although minor in the MP component, dramatically increased after EGFR-TKI therapy and indicate that the MP components feature intrinsic heterogeneity.

Tumor Spread through Air Spaces is an Important Pattern of Invasion and Impacts the Frequency and Location of Recurrences after Limited Resection for Small Stage I Lung Adenocarcinomas

INTRODUCTION

Tumor invasion in lung adenocarcinoma is defined as infiltration of stroma, blood vessels, or pleura. Based on observation of tumor spread through air spaces (STAS), we considered whether this could represent new patterns of invasion and investigated whether it correlated with locoregional versus distant recurrence according to limited resection versus lobectomy.

METHODS

We reviewed resected small (less than or equal to 2 cm) stage I lung adenocarcinomas (n = 411; 1995-2006). Tumor STAS was defined as tumor cells-micropapillary structures, solid nests, or single cells-spreading within air spaces in the lung parenchyma beyond the edge of the main tumor. Competing risks methods were used to estimate risk of disease recurrence and its associations with clinicopathological risk factors.

RESULTS

STAS was observed in 155 cases (38%). In the limited resection group (n = 120), the risk of any recurrence was significantly higher in patients with STAS-positive tumors than that of patients with STAS-negative tumors (5-year cumulative incidence of recurrence, 42.6% versus 10.9%; P < 0.001); the presence of STAS correlated with higher risk of distant (P = 0.035) and locoregional recurrence (P = 0.001). However, in the lobectomy group (n = 291), the presence of STAS was not associated with either any (P = 0.50) or distant recurrence (P = 0.76). In a multivariate analysis, the presence of tumor STAS remained independently associated with the risk of developing recurrence (hazard ratio, 3.08; P = 0.014).

CONCLUSION

The presence of STAS is a significant risk factor of recurrence in small lung adenocarcinomas treated with limited resection. These findings support our proposal that STAS should formally be recognized as a pattern of invasion in lung adenocarcinoma.

Clinical impacts of a micropapillary pattern in lung adenocarcinoma: a review

Lung adenocarcinoma with a micropapillary pattern (MPPAC) has recently drawn increased attention among researchers. Micropapillary-predominant adenocarcinoma (MPA), which is defined by micropapillary pattern (MPP), is the primary histological pattern observed semiquantitatively in 5% increments on resection specimens, and MPA was formally determined to be a new histological subtype according to the new multidisciplinary classification in 2011. According to published studies, MPPAC is most common in males and nonsmokers and is associated with lymphatic invasion, pleural invasion, and lymph node metastases. MPPAC often presents as part-solid and lobulated nodules in computed tomography scans. MPP tends to have a higher maximum standardized uptake value as determined by fluorodeoxyglucose positron emission tomography combined with computed tomography, indicating a high risk of recurrence. Molecular markers, including vimentin, napsin A, phosphorylated c-Met, cytoplasmic maspin, Notch-1, MUC1, and tumoral CD10, may have higher expression in MPPAC than other subtypes; conversely, markers such as MUC4 and surfactant apoprotein A have lower expression in MPPAC. MPPAC with EGFR mutations can benefit from treatment with EGFR tyrosine kinase inhibitors. Furthermore, a complete lobectomy may be more suitable than limited resection for MPPAC because of the low sensitivity of intraoperative frozen sections and the high risk of lymph node metastasis. MPA benefits more from adjuvant chemotherapy than do other histological subtypes, whereas MPA does not benefit from adjuvant radiotherapy. Of note, MPP is associated with poor prognosis in early-stage lung adenocarcinoma, but the prognostic value of MPP is controversial in advanced-stage lung adenocarcinoma.

Tumor islands and spread through air spaces: Distinct patterns of invasion in lung adenocarcinoma

Lung adenocarcinoma is a highly heterogeneous disease and the heterogeneity is associated with various patient outcomes even in early-stage tumors. In order to improve prognostic and predictive values, the IASLC/ATS/ERS international multidisciplinary lung adenocarcinoma classification was put forth in 2011 and it has been adopted in the recently published World Health Organization (WHO) classification of Tumours of the Lung, Pleura, Thymus and Heart 4th edition 2015, and lung adenocarcinomas are classified based on the predominant pattern. The performance of the classification in stratifying patient outcomes after resection of Stage I tumors and predicting molecular alterations has been confirmed by several studies. It also includes the category of minimally invasive adenocarcinoma (MIA) that predicts 100% 5-year recurrence free survival after curative resection similar to adenocarcinoma in situ. The diagnosis of MIA is based on not only size of the invasive component but also the absence of aggressive morphologic features such as pleural and/or lymphovascular invasion. Importantly, the WHO 2015 classification has introduced the concept of air space invasion and includes it as the exclusion criteria for MIA. The air space invasion consists of tumor islands and spread through air spaces (STAS). In this review, we will discuss the two entities and their clinical implications.

[Advances of Pulmonary Adenocarcinoma with Micropapillary Pattern]

伴微乳头结构(micropapillary pattern, MPP)肺腺癌是一种临床少见的具有高度侵袭性的恶性肿瘤，近年来因其高死亡率被人们所重视。2011年关于肺腺癌的病理新分类将其作为一种独立的病理类型，此后针对该类肺癌个体化治疗的相关研究逐渐展开。近期的相关研究发现，伴MPP肺腺癌在转移机制、临床病理学、影像学、治疗及预后方面具有显著异质性。本文对伴MPP肺腺癌转移机制及相关临床研究进展进行探讨。

A comprehensive investigation of molecular features and prognosis of lung adenocarcinoma with micropapillary component

INTRODUCTION

Both micropapillary predominant lung adenocarcinoma according to the IASLC/ATS/ERS classification and lung adenocarcinoma with a micropapillary component have been reported to be associated with poor prognosis. However, whether they have different prognosis remains undetermined.

METHODS

Out of 1302 lung adenocarcinoma patients, 21 patients with micropapillary predominant lung adenocarcinoma (MPP) and 100 patients with nonmicropapillary predominant tumors harboring a micropapillary component of at least 5% (MPC) were investigated for clinicopathologic characteristics, recurrence-free survival (RFS), overall survival (OS), and spectrum of well-identified driver mutations including EGFR, KRAS, HER2, BRAF, ALK, ROS1, and RET.

RESULTS

Twenty out of 21 (95.2%) micropapillary predominant lung adenocarcinoma harbored driver mutations in EGFR (85.7%), HER2 (4.8%), or RET (4.8%). MPP had significantly worse RFS than MPC in stage I patients (p = 0.003), but not in stages II-III patients. The overall survival was comparable between MPP and MPC regardless of disease stages. Objective response was achieved in 13 out of the 18 MPP or MPC patients with EGFR mutations who received EGFR tyrosine kinase inhibitors (TKIs) after disease recurrence. The postrecurrence survival was significantly better in EGFR-mutated patients who were treated with EGFR TKIs compared to those who did not receive TKIs (p = 0.003).

CONCLUSIONS

Micropapillary predominant lung adenocarcinoma is a disease that could be largely defined by targetable driver mutations. For stage I lung adenocarcinoma, MPP was even more likely to recur than MPC. EGFR TKIs might help to control the recurrent disease for MPP or MPC patients harboring EGFR mutations.

Classification of different patterns of pulmonary adenocarcinomas

The epidemic increase of adenocarcinoma histology accounting for more than 50% of primary lung malignancies and the advent of effective molecular targeted-therapies against specific gene alterations characterizing this tumor type have led to the reconsideration of the pathologic classification of lung cancer. The new 2015 WHO classification provided the basis for a multidisciplinary approach emphasizing the close correlation among clinical, radiologic and molecular characteristics and histopathologic pattern of lung adenocarcinoma. The terms 'bronchioloalveolar carcinoma' and 'mixed adenocarcinoma' have been eliminated, introducing the concepts of 'adenocarcinoma in situ', 'minimally invasive adenocarcinoma' and the use of descriptive predominant patterns in invasive adenocarcinomas (lepidic, acinar, papillary, solid and micropapillary patterns). 'Invasive mucinous adenocarcinoma' is the new definition for mucinous bronchioloalveolar carcinoma, and some variants of invasive adenocarcinoma have been included, namely colloid, enteric and fetal-type adenocarcinomas. A concise update of the immunomorphologic, radiological and molecular characteristics of the different histologic patterns of lung adenocarcinoma is reported here.

Clinical impact of minimal micropapillary pattern in invasive lung adenocarcinoma: prognostic significance and survival outcomes

Micropapillary subtype has recently been established to be a distinct marker for poor prognosis in lung adenocarcinomas. According to the current classification of lung adenocarcinomas, all subtypes are listed semiquantitatively in 5% increments. In other words, a minimal amount of the micropapillary pattern, precisely <5% of the entire tumor is disregarded. Therefore, we sought to assess the prognostic significance and survival outcomes in patients with a micropapillary pattern proportion of <5% of the entire tumor. A total of 525 patients with lung adenocarcinoma were classified into 3 subgroups according to the presence and proportion of micropapillary subtype: (1) ≥5% of the micropapillary pattern (n=114); (2) <5% of the micropapillary pattern (n=115); and (3) absence (<1%) of the micropapillary pattern (n=296). Sex, TNM stage, lymph node status (N status), tumor size, and predominant subtype demonstrated a significant difference among the 3 subgroups. Overall survival (OS) and disease-free survival (DFS) were significantly different among the 3 subgroups (P=0.009 and 0.001 for OS and DFS, respectively). Furthermore, OS was significantly better in patients without the micropapillary pattern (<1%) than in those with <5% (P=0.034). At multivariate analyses, age (P=0.005) and N status (P=0.005) were independent prognostic factors influencing OS. In conclusion, our results demonstrated that even a small proportion of the micropapillary pattern, specifically <5% of the entire tumor has a significant prognostic impact on OS. N status remained an independent prognostic factor that negatively influenced OS.