Adenocarcinomas With Prominent Lepidic Spread: Retrospective Review Applying New Classification of the American Thoracic Society

Challenges of the eighth edition of the American Joint Committee on Cancer staging system for pathologists focusing on early stage lung adenocarcinoma

BACKGROUND

The eighth edition of the American Joint Committee on Cancer (AJCC) staging system for lung cancer adopts new criteria for tumor size, and for determining pTis, pT1a(mi), and pT1a. The latter is based on the size of stromal invasion. It is quite challenging for lung pathologists.

METHODS

All patients who had undergone surgical resection for pulmonary adenocarcinoma (ADC) at Chung Shan Medical University Hospital between January 2014 and April 2018 were reviewed, and restaged according to the eighth AJCC staging system. The clinical characteristics and survival of patients with tumor stage 0 (pTis), I or II were analyzed.

RESULTS

In total, 376 patients were analyzed. None of the pTis, pT1a(mi), or pT1a tumors recurred during the follow-up period up to 5 years, but pT1b, pT1c, pT2a, and pT2b tumors all had a few tumor recurrences (p < 0.0001). In addition, 95.2%, 100%, and 77.5% of pTis, pT1a(mi), and pT1a tumors, respectively, had tumor sizes ≤1.0 cm by gross examination. All pTis, pT1a(mi), and pT1a tumors exhibited only lepidic, acinar, or papillary patterns histologically.

CONCLUSIONS

This study demonstrated excellent survival for lung ADC patients with pTis, pT1a(mi), and pT1a tumors when completely excised. To reduce the inconsistencies between pathologists, staging lung ADC with tumors of ≤1 cm in size grossly as pTis, pT1a(mi), or pT1a may not be necessary when the tumors exhibit only lepidic, acinar, or papillary histological patterns. A larger cohort study with sufficient follow-up data is necessary to support this proposal.

Predictors of Invasiveness in Adenocarcinoma of Lung with Lepidic Growth Pattern

Lung adenocarcinoma with lepidic growth pattern (LPA) is characterized by tumor cell proliferation along intact alveolar walls, and further classified as adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and invasive lepidic predominant adenocarcinoma (iLPA). Accurate diagnosis of lepidic lesions is critical for appropriate prognostication and management as five-year survival in patients with iLPA is lower than in those with AIS and MIA. We aimed to evaluate the accuracy of CT-guided core needle lung biopsy classifying LPA lesions and identify clinical and radiologic predictors of invasive disease in biopsied lesions. Thirty-four cases of adenocarcinoma with non-invasive lepidic growth pattern on core biopsy pathology that subsequently were resected between 2011 and 2018 were identified. Invasive LPA vs. non-invasive LPA (AIS or MIA) was defined based on explant pathology. Histopathology of core biopsy and resected tumor specimens was compared for concordance, and clinical, radiologic and pathologic variables were analyzed to assess for correlation with invasive disease. The majority of explanted tumors (70.6%) revealed invasive disease. Asian race (p = 0.03), history of extrathoracic malignancy (p = 0.02) and absence of smoking history (p = 0.03) were associated with invasive disease. CT-measured tumor size was not associated with invasiveness (p = 0.15). CT appearance of density (p = 0.61), shape (p = 0.78), and margin (p = 0.24) did not demonstrate a significant difference between the two subgroups. Invasiveness of tumors with lepidic growth patterns can be underestimated on transthoracic core needle biopsies. Asian race, absence of smoking, and history of extrathoracic malignancy were associated with invasive disease.

Combined Radiomic and Visual Assessment for Improved Detection of Lung Adenocarcinoma Invasiveness on Computed Tomography Scans: A Multi-Institutional Study

Objective

The timing and nature of surgical intervention for semisolid abnormalities are dependent upon distinguishing between adenocarcinoma-in-situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma (INV). We sought to develop and evaluate a quantitative imaging method to determine invasiveness of small, ground-glass lesions on computed tomography (CT) chest scans.

Methods

The study comprised 268 patients from 4 institutions with resected (<=3 cm) semisolid lesions with confirmed histopathological diagnosis of MIA/AIS or INV. A total of 248 radiomic texture features from within the tumor nodule (intratumoral) and adjacent to the nodule (peritumoral) were extracted from manually annotated lung nodules of chest CT scans. The datasets were randomly divided, with 40% of patients used for training and 60% used for testing the machine classifier (Training D_Train, N=106; Testing, D_Test, N=162).

Results

The top five radiomic stable features included four intratumoral (Laws and Haralick feature families) and one peritumoral feature within 3 to 6 mm of the nodule (CoLlAGe feature family), which successfully differentiated INV from MIA/AIS nodules with an AUC of 0.917 [0.867-0.967] on D_Train and 0.863 [0.79-0.931] on D_Test. The radiomics model successfully differentiated INV from MIA cases (<1 cm AUC: 0.76 [0.53-0.98], 1-2 cm AUC: 0.92 [0.85-0.98], 2-3 cm AUC: 0.95 [0.88-1]). The final integrated model combining the classifier with the radiologists’ score gave the best AUC on D_Test (AUC=0.909, p<0.001).

Conclusions

Addition of advanced image analysis via radiomics to the routine visual assessment of CT scans help better differentiate adenocarcinoma subtypes and can aid in clinical decision making. Further prospective validation in this direction is warranted.

Relationships between SUVmax of lung adenocarcinoma and different T stages, histological grades and pathological subtypes: a retrospective cohort study in China

OBJECTIVES

Cancer cell has aberrant metabolism. The purpose of this study aimed to investigate relationships between maximum standard uptake value (SUVmax）of ¹⁸fluoro-2-deoxy-d-glucose and T stages, histological grades and pathological subtypes of lung adenocarcinoma.

DESIGN

Retrospective cohort study, employing the Kruskal-Wallis, Bonferroni-Dunn and Mann-Whitney tests to compare SUVmax of different T stages, histological grades and pathological subtypes of lung adenocarcinoma.

SETTING

The outpatients who had aberrant positron emission tomography/CT (PET/CT) images in chest were enrolled this study from August 2016 to November 2018 in Shanghai, China.

PARTICIPANT

Initial 11 270 patients with suspected lung cancer who underwent PET/CT examinations were surveyed. A total of 1454 patients who were diagnosed as lung adenocarcinoma by pathologist were included in this project.

PRIMARY OUTCOME MEASURES

SUVmax value at different tumour-node-metastasis stages of lung adenocarcinoma before surgery.

RESULTS

The mean SUVmax of patients with lung adenocarcinoma was significantly elevated with the increase in T stages. There were significant evident differences in SUVmax among T1a-T1c (p<0.05). However, after the staging of patients was more than T1 stage, SUVmax of T2a, T2b, T2 visceral pleural invasion, T3 and T4 had not dramatic changes. SUVmax value of lung adenocarcinoma in the same T stage group was the highest in patients with the high grade of malignancy and solid-predominant invasive adenocarcinoma.

CONCLUSIONS

SUVmax value was significantly associated with T stages, grades of malignancy and pathological subtypes of lung adenocarcinoma.

Can computed tomography differentiate adenocarcinoma in situ from minimally invasive adenocarcinoma?

BACKGROUND

Given the subtle pathological signs of adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA), effective differentiation between the two entities is crucial. However, it is difficult to predict these conditions using preoperative computed tomography (CT) imaging. In this study, we investigated whether histological diagnosis of AIS and MIA using quantitative three-dimensional CT imaging analysis could be predicted.

METHODS

We retrospectively analyzed the images and histopathological findings of patients with lung cancer who were diagnosed with AIS or MIA between January 2017 and June 2018. We used Synapse Vincent (v. 4.3) (Fujifilm) software to analyze the CT attenuation values and performed a histogram analysis.

RESULTS

There were 22 patients with AIS and 22 with MIA. The ground-glass nodule (GGN) rate was significantly higher in patients with AIS (p < 0.001), whereas the solid volume (p < 0.001) and solid rate (p = 0.001) were significantly higher in those with MIA. The mean (p = 0.002) and maximum (p = 0.025) CT values were significantly higher in patients with MIA. The 25th, 50th, 75th, and 97.5th percentiles (all p < 0.05) for the CT values were significantly higher in patients with MIA.

CONCLUSIONS

We demonstrated that quantitative analysis of 3D-CT imaging data using software can help distinguish AIS from MIA. These analyses are useful for guiding decision-making in the surgical management of early lung cancer, as well as subsequent follow-up.

Excellent Prognosis of Patients With Invasive Lung Adenocarcinomas During Surgery Misdiagnosed as Atypical Adenomatous Hyperplasia, Adenocarcinoma In Situ, or Minimally Invasive Adenocarcinoma by Frozen Section

BACKGROUND

Our previous study revealed that intraoperative frozen section (FS) analysis could differentiate invasive lung adenocarcinoma (LUAD) accurately from preinvasive lesions. However, few articles have analyzed the clinical impact of FS errors such as underestimation of invasive adenocarcinomas (IACs), and whether complementary therapy is needed remains controversial.

RESEARCH QUESTION

What is the prognosis of patients undergoing limited resection for invasive LUAD misdiagnosed as atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS), or minimally invasive adenocarcinoma (MIA) by intraoperative FS analysis?

STUDY DESIGN AND METHODS

From 2012 through 2018, data on 3031 patients undergoing sublobar resection of AAH, AIS, or MIA diagnosed by FS analysis were collected. The concordance rate between FS analysis and final pathologic results was evaluated. To assess the clinical significance of a discrepancy between FS and final pathologic results, patients with final pathologic results of IAC were identified for prognostic evaluation.

RESULTS

When AAH, AIS, and MIA were classified together as a group, the overall concordance rate between FS and final pathologic results was 93.7%, and 192 patients (6.3%) received an upgraded diagnosis from the final pathologic results. Misdiagnosed IACs consisted of 94 patients (48.9%) with lepidic-predominant adenocarcinoma, 77 patients (40.1%) with acinar predominant adenocarcinoma, 19 patients (9.9%) with papillary predominant adenocarcinoma, one patient with solid predominant adenocarcinoma, and one patient with invasive mucinous adenocarcinoma. Among these patients, no positive N1 or N2 lymph node findings were observed. Moreover, the 5-year recurrence-free survival was still 100%, although the final pathologic results turned out to be IAC.

INTERPRETATION

Patients undergoing limited resection of invasive LUAD misdiagnosed as AAH, AIS, or MIA by FS analysis showed excellent prognoses. Sublobar resection guided by FS diagnosis would be adequate for these underestimated cases of invasive LUAD.

[Progress in Research on the Cribriform Component in Lung Adenocarcinoma]

The morbidity of lung cancer ranks top in the world. At present, lung adenocarcinoma (LUAD) is the most common histologic type of lung cancer. However, the prognoses of LUAD patients with the same subtype remain heterogeneous. Histological heterogeneity is one of the main causes of diverse prognoses of patients with LUAD. Studies have shown that there are other histologic patterns that affect the clinical outcomes of LUAD patients, in addition to the five growth patterns of invasive LUAD classified by the World Health Organization (WHO) in 2015. The cribriform component (CC) is one of the research hotspots among histopathology of LUAD. Previous studies have shown that the presence of CC can further stratify the prognoses of patients with LUAD. Along with the progressively deep insights into the aforementioned topic, researchers are dedicating to unveiling the relationships among CC and and other clinicopathological factors as well as their joint influence on the survival of LUAD patients. The review manages to generalize the latest research progress in the CC in LUAD patients.

Clinicopathologic Features and Genetic Alterations in Adenocarcinoma In Situ and Minimally Invasive Adenocarcinoma of the Lung: Long-Term Follow-Up Study of 121 Asian Patients

BACKGROUND

Adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) are both small tumors with good prognosis after surgical resection, and most of them present as ground glass opacities (GGOs) on computed tomography (CT) screening. However, the differences in clinicopathologic features and genetic alterations between AIS and MIA are poorly elaborated, and few studies have evaluated the prognosis of MIA with different invasive components. Meanwhile, the histological features of lung lesions presenting as unchanged pure GGOs are barely understood.

METHODS

Clinicopathologic features and genetic alterations of AIS (n = 59) and MIA (n = 62) presenting as GGOs were analyzed. Long-term preoperative observation (ranging from 2 to 1967 days) and postoperative follow-up (ranging from 0 to 92 months) was conducted.

RESULTS

The tumor size and consolidation/tumor ratio were significantly larger in the MIA cohort than those in the AIS cohort both on CT and microscopy images. Immunohistochemically, the expression of p53, Ki67, and cyclin D1 was higher in MIA than in AIS. The EGFR mutation rate was significantly higher in MIA, while other genetic alterations showed no differences. Six MIA cases showed recurrence or metachronous adenocarcinoma and all the cases with a predominant micropapillary invasive pattern demonstrated this feature.

CONCLUSIONS

The current CT measurements may be helpful in distinguishing AIS from MIA, but show limited utility in predicting the histology of unchanged pure GGOs. The invasive pattern may have an influence on the postoperative process of MIA; therefore, further studies are needed to evaluate the current diagnostic criteria and treatment strategy for MIA.

Stereotactic ablative radiotherapy (SABR) in early stage non-small cell lung cancer: Comparing survival outcomes in adenocarcinoma and squamous cell carcinoma

PURPOSE

Recent retrospective studies have demonstrated mixed results regarding the histologic association of squamous cell carcinoma (SCC) with reduced overall survival in patients with early-stage non-small cell lung cancer (ES-NSCLC) treated with stereotactic ablative radiotherapy (SABR).

METHODS

We queried the National Cancer Database (NCDB) for ES-NSCLC (T1-2N0, Stage I-IIA) patients with SCC or adenocarcinoma (ADC) treated with SABR. Univariable and multivariable analyses identified characteristics predictive of overall survival. Cox proportional hazard ratios with propensity adjustment were used to mitigate indication bias between the two histologic arms.

RESULTS

Ultimately 15,110 ES-NSCLC patients with either ADC (n = 8,924) or SCC (n = 6,186) were eligible for analysis. Univariable analysis demonstrated a median overall survival of 44 months and 33 months (p < 0.0001) and 5-year overall survival of 36% and 24% (p < 0.0001) in patients diagnosed with ADC and SCC, respectively. SCC histology, remained an independent predictor of worse survival on propensity score matched multivariable comparison (p < 0.0001). Patients with SCC were more likely to have T2 lesions and poorly differentiated grade. Females, African American race, T1 lesions, and age <75 years were also associated with improved survival. Conclusion SCC histology was an independent prognosticator of worse survival in patients with ES-NSCLC treated with SABR, thus corroborating the results of previous studies. Randomized, prospective studies are needed to further validate these findings.

[Factors Influencing the Progression Trend of Early Lung Cancer and CT Findings]

背景与目的

不同类型的肺部结节具有不同的体积倍增时间（volume doubling time, VDT）。目前针对不同病理类型早期肺腺癌VDT的研究较少。本研究通过回顾性分析143例早期肺腺癌的影像资料，探讨早期肺腺癌的进展趋势及相关影响因素，为临床制订其随访策略提供参考。

方法

依据2015版世界卫生组织肺肿瘤分类标准和第8版肿瘤肿瘤-淋巴结-转移（tumor-node-metastasis, TNM）分期标准，对143例早期肺腺癌进行分类及分期。参考修正版Schwartz公式计算不同病理类型肺腺癌的VDT。

结果

143例早期肺腺癌中，有50例（34.97%）出现进展，多因素分析显示影响因素包括随访时间、结节大小、病理类型、结节类型和病理分期。附壁生长为主型肺腺癌（lepidic predominant adenocarcinoma, LPA）的VDT为（594±272）d，伴少量附壁生长成分浸润性腺癌的VDT为（520±285）d，完全浸润性腺癌的VDT为（371±183）d，3类进展性早期肺腺癌的VDT有统计学差异（P=0.044）。

结论

在早期肺腺癌中，约有35%的肿瘤处于进展阶段，是否含有附壁生长成分是影响肿瘤进展速度的重要因素。

Predictive accuracy of lepidic growth subtypes in early-stage adenocarcinoma of the lung by quantitative CT histogram and FDG-PET

OBJECTIVES

The aim of this study was to analyze the accuracy of computed tomography (CT) and F-18 fluorodeoxyglucose-positron emission tomography/CT (FDG-PET/CT) to distinguish lepidic growth adenocarcinoma (LGA), including adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and lepidic-predominant adenocarcinoma, all of which have favorable survival outcomes, from the more aggressive and invasive non-LGA subtypes.

MATERIALS AND METHODS

We identified 225 patients with c-0/I adenocarcinoma of the lung who underwent PET/CT and 3DCT followed by complete resection. Maximum standardized uptake values (SUVmax) of FDG and several histogram parameters were analyzed. Histological grades were classified according to the predominant subtype (G1: lepidic; G3: micropapillary or solid; and G2: subtypes other than G1/G3).

RESULTS

The proportion of pathological invasive factors (lymphatic vessel involvement/blood vessel invasion/pleural invasion/lymph node metastasis) of patients with preinvasive adenocarcinoma, G1, G2, and G3 tumors were 0%, 3.6%, 48.0%, and 100%, respectively; p <  0.001). Multivariate analysis with CT-related parameters demonstrated that 75^th percentile CT attenuation value (75^th%, p <  0.001) and maximum CT attenuation value (maxCT, p =  0.009) were associated with incidence of non-LGA, whereas the value of SUVmax demonstrated a significant correlation (p <  0.001). When all patients were dichotomized according to ground-glass opacities (GGO)/solid-dominancy for CT maximum diameter, a significant correlation with non-LGA was shown in patients with solid-dominant tumor on SUVmax (p <  0.001) and with GGO-dominant tumor on 75^th% (p =  0.006) and maxCT (p =  0.007). The combination of one of the two significant histogram parameters and SUVmax revealed higher predictive performance for pathological high malignant features (positive pathological invasive factors, non-LGA, and the highly malignant subtype covering G2 with moderately or poorly-differentiated carcinoma and G3) than the individual use of either factor.

CONCLUSION

The 75^th%, maxCT, and SUVmax were highly useful in distinguishing LGA from non-LGA in c-0/I adenocarcinoma.

Clinicopathological Characteristics and Mutations Driving Development of Early Lung Adenocarcinoma: Tumor Initiation and Progression

Lung cancer is the leading cause of cancer-related deaths worldwide, with lung adenocarcinoma representing the most common lung cancer subtype. Among all lung adenocarcinomas, the most prevalent subset develops via tumorigenesis and progression from atypical adenomatous hyperplasia (AAH) to adenocarcinoma in situ (AIS), to minimally invasive adenocarcinoma (MIA), to overt invasive adenocarcinoma with a lepidic pattern. This stepwise development is supported by the clinicopathological and molecular characteristics of these tumors. In the 2015 World Health Organization classification, AAH and AIS are both defined as preinvasive lesions, whereas MIA is identified as an early invasive adenocarcinoma that is not expected to recur if removed completely. Recent studies have examined the molecular features of lung adenocarcinoma tumorigenesis and progression. EGFR-mutated adenocarcinoma frequently develops via the multistep progression. Oncogene-induced senescence appears to decrease the frequency of the multistep progression in KRAS- or BRAF-mutated adenocarcinoma, whose tumor evolution may be associated with epigenetic alterations and kinase-inactive mutations. This review summarizes the current knowledge of tumorigenesis and tumor progression in early lung adenocarcinoma, with special focus on its clinicopathological characteristics and their associations with driver mutations (EGFR, KRAS, and BRAF) as well as on its molecular pathogenesis and progression.

Expression of PD-L1 correlates with pleomorphic morphology and histological patterns of non-small-cell lung carcinomas

AIMS

As immunomodulatory therapy is being integrated into treatment regimens for non-small-cell lung carcinoma, we aimed to prospectively collect data on the immunohistochemical profile of tumours assessed in our institution and to correlate this with morphological tumour features.

METHODS AND RESULTS

Immunohistochemistry for programmed death-ligand 1 (PD-L1) was considered to be adequate when >100 tumour cells were seen microscopically. When adequate, PD-L1 staining was scored as <1%, ≥1-49% or ≥50% positive membrane staining within tumour cells only. There were 197 assessable cases, of which 87% of those with pleomorphic features (n = 39) showed ≥50% positivity for PD-L1 expression, as compared with only 33% of cases without pleomorphic features (P < 0.05) (90% versus 25% in resected cases). Further correlation of PD-L1 expression with architectural patterns within the tumours was performed in 74 adenocarcinoma resections. All invasive mucinous adenocarcinomas scored <1%. All lepidic components in non-mucinous adenocarcinoma resections scored <1%. Thirty-five per cent of the acinar/papillary components and 53% of the solid/micropapillary components were positive for PD-L1 expression.

CONCLUSIONS

There are significant differences in PD-L1 expression in relation to histological patterns, with particularly high levels in those with pleomorphic features and low/undetectable levels in invasive mucinous adenocarcinomas and the lepidic components of non-mucinous adenocarcinomas. Assessment of PD-L1 expression in a resected adenocarcinoma with a lepidic component may therefore not be reliable when immumodulatory therapy for recurrent disease is being considered, and either re-biopsy or limiting assessment to the invasive component may be more appropriate.

Prognostic significance of histologic classification and tumor disappearance rate by computed tomography in lung cancer

Background

We investigated the prognostic value of the International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification and assessed the relationship between pathologic invasiveness and tumor disappearance rate (TDR) in lung adenocarcinoma with ground-glass opacity (GGO).

Methods

We reviewed data from 202 consecutive patients operated on between 2000 and 2009 for clinical T1-2N0 lung adenocarcinoma with GGO and reclassified their histologic subtypes according to the IASLC/ATS/ERS classification. Thirty-nine patients had adenocarcinoma in situ (AIS), 29 minimally invasive adenocarcinoma (MIA), 75 lepidic predominant invasive adenocarcinoma (LPA), and 59 non-lepidic predominant invasive adenocarcinoma (NLPA). Survival outcomes were compared according to histologic subtype and TDR.

Results

The mean age was 58 years and 101 patients (50%) were male. Lobectomy was performed in 161 patients (79.7%), wedge resection in 34 (16.8%), and segmentectomy in 7 (3.5%). Patients with AIS, MIA, and LPA had significantly smaller tumor sizes, earlier pathologic T stages, and lower incidences of lymphatic/pleural invasion than those with NLPA. The 5-year recurrence-free survival (RFS) rates were 95.1%, 94.5%, and 87.6% in the AIS + MIA, LPA, and NLPA groups, respectively (P=0.029). Tumors with a TDR>75% were associated with lepidic predominant histologic subtype and less pathologic invasiveness. The 5-year RFS rates were 97.4% in tumors with a TDR >75% and 87.8% in tumors with a TDR ≤75% (P=0.0009).

Conclusions

Histologic subtype according to the IASLC/ATS/ERS classification and TDR both correlated with pathologic invasiveness and predicted survival in patients with lung adenocarcinoma with GGO.

Clinical Relevance of Different Papillary Growth Patterns of Pulmonary Adenocarcinoma

Growth patterns of pulmonary adenocarcinoma (ADC) have high prognostic impact and are accepted as a novel classification system for this entity. However, specifically for the papillary pattern, divergent data with respect to prevalence, clinical associations, and prognostic impact have been reported. By evaluating 674 resected pulmonary ADCs containing 308 cases with a papillary component and 101 papillary predominant cases, we documented differences in the morphologic composition of papillary growth patterns and delineated 3 different types. The different types were correlated with pathologic and clinical data including survival. Type 3 papillary cases with any or predominant papillary growth were associated with extensive spread through alveolar spaces, high proliferation, higher stage, low rates of EGFR mutations, and smoking, whereas type 1 papillary tumors showed the opposite associations. The subclassification of papillary growth revealed type-specific associations for overall and disease-free survival (disease-free survival type 1: 67.1 mo, type 2: 56.8 mo, type 3: 49.9 mo, P=0.025). The presence of any papillary type 3 pattern was a predominant pattern independent predictor of worse overall survival (hazard ratio=2.5, P=0.02). For a future grading system of lung ADC, categorization of papillary growth in 1 single category might not be adequate, as this pattern contains a heterogenous mix of tumors with a divergent prognosis. We suggest that papillary pattern types should be separated to further improve the prognostic power of ADC growth pattern analysis.

Diagnosis of lung adenocarcinoma in situ and minimally invasive adenocarcinoma from intraoperative frozen sections: an analysis of 136 cases

AIMS

To determine the diagnostic accuracy and contraindications for intraoperative diagnosis of lung adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) from frozen sections.

METHODS

A retrospective analysis of data from 136 patients pathologically diagnosed with early-stage (T1N0M0) AIS or MIA from paraffin-embedded sections. The rate of concordance between the diagnoses from intraoperative frozen sections and paraffin-embedded sections was determined, and the interpretive features that contributed to errors and deferrals in frozen-section diagnoses were identified.

RESULTS

Of the 136 patients, diagnoses from frozen sections and paraffin-embedded sections were concordant in 86 (63.24%) cases intraoperatively diagnosed with AIS or MIA, and 44 (32.35%) cases were intraoperatively diagnosed with adenocarcinoma as the range of infiltration could not be determined from the frozen sections. From the remaining six (4.41%) cases, the frozen section and paraffin-embedded section diagnoses were discordant. The reasons for frozen section errors and deferrals included larger tumour volume, tumour located close to the visceral pleura, interstitial inflammation or fibrosis, absence of prominent atypia and differential morphology in the deeper levels of the paraffin block.

CONCLUSIONS

Diagnosis of AIS and MIA from intraoperative frozen sections is feasible. We provide several modifications that may improve the diagnostic accuracy of intraoperative frozen sections for early-stage lung adenocarcinoma.

The IASLC Lung Cancer Staging Project: Proposals for Coding T Categories for Subsolid Nodules and Assessment of Tumor Size in Part-Solid Tumors in the Forthcoming Eighth Edition of the TNM Classification of Lung Cancer

This article proposes codes for the primary tumor categories of adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) and a uniform way to measure tumor size in part-solid tumors for the eighth edition of the tumor, node, and metastasis classification of lung cancer. In 2011, new entities of AIS, MIA, and lepidic predominant adenocarcinoma were defined, and they were later incorporated into the 2015 World Health Organization classification of lung cancer. To fit these entities into the T component of the staging system, the Tis category is proposed for AIS, with Tis (AIS) specified if it is to be distinguished from squamous cell carcinoma in situ (SCIS), which is to be designated Tis (SCIS). We also propose that MIA be classified as T1mi. Furthermore, the use of the invasive size for T descriptor size follows a recommendation made in three editions of the Union for International Cancer Control tumor, node, and metastasis supplement since 2003. For tumor size, the greatest dimension should be reported both clinically and pathologically. In nonmucinous lung adenocarcinomas, the computed tomography (CT) findings of ground glass versus solid opacities tend to correspond respectively to lepidic versus invasive patterns seen pathologically. However, this correlation is not absolute; so when CT features suggest nonmucinous AIS, MIA, and lepidic predominant adenocarcinoma, the suspected diagnosis and clinical staging should be regarded as a preliminary assessment that is subject to revision after pathologic evaluation of resected specimens. The ability to predict invasive versus noninvasive size on the basis of solid versus ground glass components is not applicable to mucinous AIS, MIA, or invasive mucinous adenocarcinomas because they generally show solid nodules or consolidation on CT.

Prognosis and status of lymph node involvement in patients with adenocarcinoma in situ and minimally invasive adenocarcinoma-a systematic literature review and pooled-data analysis

BACKGROUND

Adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) have been brought up that substitute for bronchioloalveolar carcinoma (BAC), according to the new classification of lung adenocarcinoma. There has been increasing opinions that argues for the adjustment of lymph node disposition in patients with such early stage tumors. Therefore, we sought to overview the prognosis and status of lymph node involvement in AIS/MIA patients.

METHODS

PubMed, Springer and Ovid databases were searched for relevant studies. Data was extracted and results summarized to demonstrate the disposition of lymph nodes in AIS/MIA.

RESULTS

Twenty-three studies consisting of 6,137 lung adenocarcinoma were included. AIS/MIA accounted for 821 of the total 6,137. All included patients received curative surgery. After a review of the summarized data we found that only one patient (with MIA) had N1 node metastasis, N2 disease was not found in any of the included patients. In concordance with this, studies that reported 5-year disease free survival (5-year DFS) have almost 100% rate.

CONCLUSIONS

Our findings indicated that patients with AIS/MIA have good survival prognosis after surgical resection, and that recurrence and lymph node metastasis in these patients is rare. Therefore, we strongly encouraged further studies to determine the role of different lymph node disposition strategies.

Using frozen section to identify histological patterns in stage I lung adenocarcinoma of ≤ 3 cm: accuracy and interobserver agreement

AIMS

The IASLC/ATS/ERS classification of lung adenocarcinoma provides a prognostically significant histological subclassification. The aim of this study was to investigate the accuracy, limitations and interobserver agreement of frozen sections for predicting histological subtype.

METHODS AND RESULTS

Frozen section and permanent section slides from 361 resected stage I lung adenocarcinomas ≤ 3 cm in size were reviewed for predominant histological subtype and the presence or absence of lepidic, acinar, papillary, micropapillary and solid patterns. Fifty cases were additionally reviewed by three pathologists to determine interobserver agreement. To test the accuracy of frozen section in judging degree of invasion, five pathologists reviewed frozen section slides from 35 cases with a predominantly lepidic pattern. There was moderate agreement on predominant histological subtype between frozen sections and final diagnosis (κ = 0.565). Frozen sections had high specificity for micropapillary and solid patterns (94% and 96%, respectively), but sensitivity was low (37% and 69%, respectively). The interobserver agreement was satisfactory (κ > 0.6, except for the acinar pattern).

CONCLUSIONS

Frozen section can provide information on the presence of aggressive histological patterns-micropapillary and solid-with high specificity but low sensitivity. It was difficult to predict the predominant pattern on the basis of frozen sections, mostly because of sampling issues.

The new histologic classification of lung primary adenocarcinoma subtypes is a reliable prognostic marker and identifies tumors with different mutation status: the experience of a French cohort

BACKGROUND

Histologic classification of lung adenocarcinoma subtype has a prognostic value in most studies. However, lung adenocarcinoma characteristics differ across countries. Here, we aimed at validating the prognostic value of this classification in a large French series of lung adenocarcinoma.

METHODS

We reviewed 407 consecutive lung adenocarcinomas operated on between 2001 and 2005 and reclassified them according to the International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification and subsequently graded them into low, intermediate, and high grade. We analyzed the relevance of this classification according to clinical, pathologic, and molecular analysis.

RESULTS

Patients (median age, 61 years; 288 men) underwent lobectomy (n = 378) or pneumonectomy (n = 29). Patients' overall survival at 5 and 10 years was 53.2% and 32.6%, respectively. Union for International Cancer Control stage distribution was 189 stage I, 104 stage II, 107 stage III, and seven stage IV. Low-grade tumor was found in one patient, intermediate grade in 275 patients, and high grade in 131 patients. KRAS and EGFR mutations were detected in 34% and 9.6%, respectively. Histologic grade was significantly correlated with extent of resection (P = .01), thyroid transcriptional factor-1 expression (P = .00000001), vascular emboli (P = .03), and EGFR mutations (P = .01). Mucinous adenocarcinomas were associated with KRAS mutations (P = .003). At univariate analysis, age, extent of resection, histologic grade, pleural invasion, vascular emboli, pathologic T and N, and stage were predictive of survival. At multivariate analysis, age (P = .0001), histologic grade (P = .03), and stage (P = .000003) were independent prognostic factors.

CONCLUSIONS

IASLC/ATS/ERS classification of lung adenocarcinomas predicts survival in French population. Histologic grade correlates with clinical, pathologic and molecular parameters suggesting different oncogenic pathways.

Early lung cancer with lepidic pattern: adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic predominant adenocarcinoma

PURPOSE OF REVIEW

This review gives a comprehensive overview on recent developments in the classification of neoplastic lung lesions with lepidic growth patterns, comprising the adenocarcinoma (ADC) precursor lesions atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS), and minimally invasive adenocarcinoma (MIA) as well as lepidic predominant adenocarcinoma (LPA).

RECENT FINDINGS

The concept of a continuum between the precursor lesions AAH and AIS to MIA and frankly invasive ADC is backed by a wealth of recent data showing a gradual decrease in overall survival from 100% for AAH, AIS, and MIA to moderately lower rates for LPA. Further, it has been shown that the morphologic categorization of these tumors can be done with reasonable reliability and that nonmucinous lepidic tumors show distinct molecular alterations with high rates of epidermal growth factor receptor mutations. Importantly, lepidic tumor growth is also mirrored by specific characteristics in computed tomography images, arguing for a combined assessment of histomorphology and imaging data for an optimized classification of lepidic neoplasms.

SUMMARY

The validity and clinical importance of the novel concept of ADC precursor lesions and LPA have been confirmed by clinical, radiological, morphological, and molecular data. Thereby, it has evolved into a valuable tool to aid in clinical decision-making.

Expression of EGFR and molecules downstream to PI3K/Akt, Raf-1-MEK-1-MAP (Erk1/2), and JAK (STAT3) pathways in invasive lung adenocarcinomas resected at a single institution

Therapies targeting EGFR are effective in treating tumors that harbor molecular alterations; however, there is heterogeneity in long-term response to these therapies. We retrospectively analyzed protein expression of EGFR, Stat3, phospho-Akt, and phospho-Erk1/2 by immunohistochemistry in a series of resected cases from a single institution, correlated with clinicopathological variables. There were 96 patients, with the majority of cases being of low stage tumors (17 pT1a, 23 pT1b, 30 pT2a, and 18 pT2b). Histologic subtypes were 45 acinar predominant, 2 cribriform, 25 solid, 7 papillary, 11 lepidic, and 4 mucinous tumors. The EGFR score was higher in tumors with vascular invasion (P = 0.013), in solid and cribriform acinar histology, and in high stage tumors (P = 0.006 and P = 0.01). EGFR was more likely overexpressed in solid compared to lepidic tumors (P = 0.02). Acinar tumors had the highest rate of ERK1/2 positivity (19%). There was a strong correlation among positivity for ERCC1 and other markers, including STAT3 (P = 0.003), Akt (P = 0.02), and ERK1/ERK2 (P = 0.0005). Expression of molecules downstream to EGFR varied from 12% to 31% of tumors; however, the expression did not directly correlate to EGFR expression, which may suggest activation of the cascades through different pathways. The correlation of protein expression and the new lung adenocarcinoma classification may help in the understanding of activated pathways of each tumor type, which may act in the oncogenesis and drug resistance of these tumors.

Advances in lung adenocarcinoma classification: a summary of the new international multidisciplinary classification system (IASLC/ATS/ERS)

Due to advances in the understanding of lung adenocarcinoma since the advent of its 2004 World Health System classification, an international multidisciplinary panel [sponsored by the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS)] has recently updated the classification system for lung adenocarcinoma, the most common histologic type of lung cancer. Here, we summarize and highlight the new criteria and terminology, certain aspects of its clinical relevance and its potential treatment impact, and future avenues of research related to the new system.

The lung adenocarcinoma guidelines: what to be considered by surgeons

In 2011 the International Association for the Study of Lung Cancer (IASLC), the American Thoracic Society (ATS), and the European Respiratory Society (ERS), have proposed a new subclassification of lung adenocarcinomas. This new classification was founded on an evidence-based approach to a systematic review of 11,368 citations from the related literature. Validation has involved projects relating to histologic and cytologic analysis of small biopsy specimens, histologic subtyping, grading, and observer variation among expert pathologists. As enormous resources are being spent on trials involving molecular and therapeutic aspects of adenocarcinoma of the lung, the development of standardized criteria is of great importance and should help advance the field, increasing the impact of research, and improving patient care. This classification is needed to assist in determining patient therapy and predicting outcome. The 2011 IASLC/ATS/ERS adenocarcinoma classification can have an impact on TNM staging. It may help in comparing histologic characteristics of multiple lung adenocarcinomas to determine whether they are intrapulmonary metastases versus separate primaries. Use of comprehensive histologic subtyping along with other histologic characteristics has been shown to have good correlation with molecular analyses and clinical behavior. Also, it may be more meaningful clinically to measure tumor size in lung adenocarcinomas that have a lepidic component by using invasive size rather than total size to determine the size T factor.

The correlation of the International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification with prognosis and EGFR mutation in lung adenocarcinoma

BACKGROUND

The purpose of this study was to validate the prognostic effect and the frequency of mutations in the gene expressing epidermal growth factor receptor (EGFR) in lung adenocarcinoma of Japanese patients, on the basis of the new adenocarcinoma classification proposed by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society.

METHODS

The new classification was used to reclassify 486 adenocarcinomas. The percentage of each histopathologic subtype and the predominant pattern were determined. EGFR mutation was also investigated. The relationship between these results and clinicopathologic backgrounds was investigated statistically.

RESULTS

No patients with adenocarcinoma in situ or minimally invasive adenocarcinoma died within the follow-up periods, followed by patients with lepidic predominant. Patients with papillary or acinar predominant, or invasive mucinous adenocarcinoma, showed almost similar overall survival (OS). The patients with solid predominant and micropapillary predominant showed the worst OS. Multivariate analysis showed that the new classification was an independent predictor of OS. The frequency of EGFR mutation was adenocarcinoma in situ (62%), minimally invasive adenocarcinoma (60%), lepidic (77%), acinar (49%), papillary (50%), solid (28%), micropapillary (43%), and invasive mucinous adenocarcinoma (0%).

CONCLUSIONS

This new adenocarcinoma classification is a very useful predictive marker to plan and determine a therapeutic strategy for lung adenocarcinoma.

Prognostic significance of adenocarcinoma in situ, minimally invasive adenocarcinoma, and nonmucinous lepidic predominant invasive adenocarcinoma of the lung in patients with stage I disease

According to the IASLC/ATS/ERS classification, the lepidic predominant pattern consists of 3 subtypes: adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and nonmucinous lepidic predominant invasive adenocarcinoma. We reviewed tumor slides from 1038 patients with stage I lung adenocarcinoma, recording the percentage of each histologic pattern and measuring the invasive tumor size. Tumors were classified according to the IASLC/ATS/ERS classification: 2 were AIS, 34 MIA, and 103 lepidic predominant invasive. Cumulative incidence of recurrence (CIR) was used to estimate the probability of recurrence. Patients with AIS and MIA experienced no recurrences. Patients with lepidic predominant invasive tumors had a lower risk for recurrence (5-y CIR, 8%) than nonlepidic predominant tumors (n=899; 19%; P=0.003). Patients with >50% lepidic pattern tumors experienced no recurrences (n=84), those with >10% to 50% lepidic pattern tumors had an intermediate risk for recurrence (n=344; 5-y CIR, 12%), and those with ≤10% lepidic pattern tumors had the highest risk (n=610; 22%; P<0.001). CIR was lower for patients with ≤2 cm tumors than for those with >2 to 3 cm tumors (for both total and invasive tumor size), with the difference more pronounced for invasive tumor size (5-y CIR, 13% vs. 21% [total size; P=0.022] and 12% vs. 27% [invasive size; P<0.001]). Most patients with lepidic predominant adenocarcinoma who experienced a recurrence had potential risk factors, including sublobar resection with close margins (≤0.5 cm; n=2), 20% to 30% micropapillary component (n=2), and lymphatic or vascular invasion (n=2). It therefore may be possible to identify lepidic predominant adenocarcinomas that carry a low or high risk for recurrence.

Predictive value of the international association for the study of lung cancer/American Thoracic Society/European Respiratory Society classification of lung adenocarcinoma in tumor recurrence and patient survival

PURPOSE

This study investigated the pattern of recurrence of lung adenocarcinoma and the predictive value of histologic classification in resected lung adenocarcinoma using the new International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification system.

PATIENTS AND METHODS

Histologic classification of 573 patients undergoing resection for lung adenocarcinoma was determined according to the IASLC/ATS/ERS classification system, and the percentage of each histologic component (lepidic, acinar, papillary, micropapillary, and solid) was recorded. The pattern of recurrence of those components and their predictive value were investigated.

RESULTS

The predominant histologic pattern was significantly associated with sex (P < .01), invasive tumor size (P < .01), T status (P < .01), N status (P < .01), TNM stage (P < .01), and visceral pleural invasion (P < .01). The percentage of recurrence was significantly higher in micropapillary- and solid-predominant adenocarcinomas (P < .01). Micropapillary- and solid-predominant adenocarcinomas had a significantly higher possibility of developing initial extrathoracic-only recurrence than other types (P < .01). The predominant pattern group (micropapillary or solid v lepidic, acinar, or papillary) was a significant prognostic factor in overall survival (OS; P < .01), probability of freedom from recurrence (P < .01), and disease-specific survival (P < .01) in multivariable analysis. For patients receiving adjuvant chemotherapy, solid-predominant adenocarcinoma was a significant predictor for poor OS (P = .04).

CONCLUSION

In lung adenocarcinoma, the IASLC/ATS/ERS classification system has significant prognostic and predictive value regarding death and recurrence. Solid-predominant adenocarcinoma was also a significant predictor in patients undergoing adjuvant chemotherapy. Prognostic and predictive information is important for stratifying patients for aggressive adjuvant chemoradiotherapy.

Current readings: pathology, prognosis, and lung cancer

The 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society international multidisciplinary classification of lung adenocarcinoma introduced the new categories of adenocarcinoma in situ, minimally invasive adenocarcinoma, and invasive mucinous adenocarcinoma, and replaced the category of mixed subtype adenocarcinoma with lepidic, acinar, papillary, micropapillary, and solid predominant adenocarcinoma. The aim of this manuscript is to evaluate whether the new classification can be applied successfully in determining prognosis of surgically resected patients. Six consecutive clinicopathologic studies using the new classification that were published between spring 2011 and fall 2012 were reviewed. Overall, they demonstrated excellent outcome for adenocarcinoma in situ and minimally invasive adenocarcinoma; intermediate outcome for lepidic, acinar, and papillary predominant adenocarcinoma; and poor outcome for solid and micropapillary predominant adenocarcinoma and invasive mucinous adenocarcinoma. As the new classification remains a proposal at this time, it is hoped that thoracic surgeons will play a leading role in its worldwide dissemination for clinical care and research.

Cancer stem cell-related marker expression in lung adenocarcinoma and relevance of histologic subtypes based on IASLC/ATS/ERS classification

Background

The cancer stem cell (CSC) theory has been proposed to explain tumor heterogeneity and the carcinogenesis of solid tumors. The aim of this study was to clarify the clinical role of CSC-related markers in patients with lung adenocarcinoma and to determine whether each CSC-related marker expression correlates with the histologic subtyping proposed by the International Association for the Study of Lung Cancer (IASLC), the American Thoracic Society (ATS), and the European Respiratory Society (ERS) classifications.

Methods

We reviewed data for all 103 patients in whom complete resection of adenocarcinoma had been performed. Expression of CSC-related markers, ie, aldehyde dehydrogenase 1A1 (ALDH1A1), aldo-keto reductase 1C family member 1 (AK1C1), and 1C family member 3 (AK1C3), was examined using immunostaining on whole-mount tissue slides, and the tumors were reclassified according to the IASLC/ATS/ERS classification.

Results

ALDH1A1 expression was observed in 66.0% of tumors, AK1C1 in 62.7%, and AK1C3 in 86.1%. Immunoreactivities with the frequency of mean expression of ALDH1A1 in papillary predominant adenocarcinoma were significantly higher than those of solid predominant adenocarcinoma (P<0.05). Papillary predominant adenocarcinoma had significantly lower expression of AK1C1 when compared with noninvasive or solid predominant adenocarcinomas (P<0.05). On multivariate analysis, larger tumor size (hazards ratio 1.899, P=0.044), lymph node metastasis (hazards ratio 2.702, P=0.005), and low expression of ALDH1A1 (hazards ratio 3.218, P<0.001) were shown to be independently associated with an unfavorable prognosis.

Conclusion

Immunohistochemistry of ALDH1A1 expression is strongly associated with prognosis. Expression of each CSC-related marker varies according to subtype, suggesting that a comprehensive histologic subtyping approach in the IASLC/ATS/ERS classification provides new molecular biology insights into the genesis of lung adenocarcinoma according to CSC theory.

The new 2011 international association for the study of lung cancer/american thoracic society/european respiratory society classification of lung adenocarcinoma in resected specimens: clinicopathologic relevance and emerging issues

Pathologists play an increasingly important role in personalized medicine for patients with lung cancer as a result of the newly recognized relationship between histologic classification and molecular change. In 2011, the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) proposed a new architectural classification for invasive lung adenocarcinomas to provide uniform terminology and diagnostic criteria. This review highlighted the evolution of the classification of lung adenocarcinomas in resected specimens with special respect to both histologic subtyping and invasion. Histologic subtyping of lung adenocarcinoma has been updated based on five major predominant patterns. New concepts of adenocarcinoma in situ and minimally invasive adenocarcinomas have been introduced to define the condition of patients who are expected to have excellent survival. Although the new IASLC/ATS/ERS classification has promising clinical relevance, significant clarification remains necessary for the definitions of subtyping and invasion. More precise definitions and subsequent better education on the interpretation of terminology will be helpful for future studies.

The utility of the proposed IASLC/ATS/ERS lung adenocarcinoma subtypes for disease prognosis and correlation of driver gene alterations

BACKGROUND

The present study aimed to determine the ability of the revised International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification of lung adenocarcinoma to predict patient survivals and driver gene alterations.

PATIENTS AND METHODS

A reclassification of 904 surgically resected adenocarcinomas was performed. The results were statistically analyzed to examine the correlation between the classification and overall survival (OS) using Cox regression analyses, and integrated discrimination improvement (IDI) analyses.

RESULTS

The 5-year OS rates for adenocarcinomas in situ (AIS) or minimally invasive adenocarcinoma (MIA) were 98%. Five-year OS rates of Lepidic-, acinar-, papillary-, micropapillary-, and solid-predominant adenocarcinomas was 93%, 67%, 74%, 62%, and 58%, respectively. The IDI estimates revealed that classification of ADC into the 7 subgroups had a higher estimated (0.0175) than did the combined histological grouping (AIS + MIA, lepidic + acinar + papillary, micropapillary + solid + others) (0.0111). Epidermal growth factor receptor mutations, KRAS gene mutations, and anaplastic lymphoma kinase gene alterations were statistically prevalent in papillary-predominant (P = 0.00001), invasive mucinous (P = 0.00001), and micropapillary- and acinar-predominant (P = 0.00001) adenocarcinomas, respectively.

CONCLUSIONS

The new classification reflects disease prognosis, and was also associated with driver gene alterations.

Validation of the IASLC/ATS/ERS lung adenocarcinoma classification for prognosis and association with EGFR and KRAS gene mutations: analysis of 440 Japanese patients

INTRODUCTION

This study aimed to validate the utility of the new histological classification proposed by the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) for identifying the prognostic subtypes of adenocarcinomas in Japanese patients; correlations between the classification and the presence of EGFR or KRAS mutation status were also investigated.

METHODS

We retrospectively reviewed 440 patients with lung adenocarcinoma, who underwent resection. The tumors were classified according to the IASLC/ATS/ERS classification. EGFR and KRAS mutations were detected using the established methods.

RESULTS

Five-year disease-free survival rates were: 100% for adenocarcinoma in situ (n = 20) and minimally invasive adenocarcinoma (n = 33), 93.8% for lepidic-predominant adenocarcinoma (n = 36), 88.8% for invasive mucinous adenocarcinoma (n = 10), 66.7% for papillary-predominant adenocarcinoma (n = 179), 69.7% for acinar-predominant adenocarcinoma (n = 61), 43.3% for solid-predominant adencoarcinoma (n = 78), and 0% for micropapillary-predominant adenocarcinoma (n = 19). Multivariate analysis revealed that the new classification was an independent predictor of disease-free survival. EGFR and KRAS mutations were detected in 90 cases (53.9%) and 21 cases (13.3%), respectively; EGFR mutations were significantly associated with adenocarcinoma in situ, minimally invasive adenocarcinoma, lepidic- and papillary-predominant adenocarcinoma, and KRAS mutations adenocarcinomas with mucinous tumor subtypes.

CONCLUSIONS

We found that the IASLC/ATS/ERS classification identified prognostic histologic subtypes of lung adenocarcinomas among Japanese patients. Histologic subtyping and molecular testing for EGFR and KRAS mutations can help predict patient prognosis and select those who require adjuvant chemotherapy.

New pathologic classification of lung cancer: relevance for clinical practice and clinical trials

We summarize significant changes in pathologic classification of lung cancer resulting from the 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) lung adenocarcinoma classification. The classification was developed by an international core panel of experts representing IASLC, ATS, and ERS with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. Because 70% of patients with lung cancer present with advanced stages, a new approach to small biopsies and cytology with specific terminology and criteria focused on the need for distinguishing squamous cell carcinoma from adenocarcinoma and on molecular testing for EGFR mutations and ALK rearrangement. Tumors previously classified as non-small-cell carcinoma, not otherwise specified, because of the lack of clear squamous or adenocarcinoma morphology should be classified further by using a limited immunohistochemical workup to preserve tissue for molecular testing. The terms "bronchioloalveolar carcinoma" and "mixed subtype adenocarcinoma" have been discontinued. For resected adenocarcinomas, new concepts of adenocarcinoma in situ and minimally invasive adenocarcinoma define patients who, if they undergo complete resection, will have 100% disease-free survival. Invasive adenocarcinomas are now classified by predominant pattern after using comprehensive histologic subtyping with lepidic, acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype with poor prognosis. Former mucinous bronchioloalveolar carcinomas are now called "invasive mucinous adenocarcinoma." Because the lung cancer field is now rapidly evolving with new advances occurring on a frequent basis, particularly in the molecular arena, this classification provides a much needed standard for pathologic diagnosis not only for patient care but also for clinical trials and TNM classification.

Relationship between lung adenocarcinoma histological subtype and patient prognosis

PURPOSE

Lung adenocarcinoma (AC) demonstrates various histological subtypes within the tumour tissue. A panel established jointly by the IASLC, ATS and ERS classified invasive lung ACs based on the predominant histological subtype. We examined the distribution of tumours in lung AC patients according to histological subtype and analysed the effects of this classification on survival.

METHODS

The records of patients who had pulmonary resection for lung cancer between January 2000 and December 2009 were reviewed and 226 lung AC patients who fulfilled the inclusion criteria were identified. Histological subtypes of the ACs and their ratios in the tumour tissue were determined. Tumours were classified according to the predominant histological subtype and subsequently graded. The relationship between the predominant histological subtype, grade and survival were analysed.

RESULTS

Tumours were predominantly acinar in 99 cases (43.8%), solid in 89 (39.3%), lepidic in 20 (8.8%), and papillary in 11 (4.8%), whereas 7 tumours (3%) were variants of AC. Stage significantly affected survival (p = 0.001); however, the predominant histological subtype had no significant effect. The 5-year survival rate for patients with histologically grade II tumours was 48.6%, whereas that in patients with grade III tumours was 56%. (p = 0.69).

CONCLUSION

Invasive lung ACs may be defined by their predominant histological subtype. However, it is not yet possible to conclude that this classification is related to survival.