Micropapillary pattern: a distinct pathological marker to subclassify tumours with a significantly poor prognosis within small peripheral lung adenocarcinoma (<=20 mm) with mixed bronchioloalveolar and invasive subtypes (Noguchi's type C tumours)

A semi-supervised learning framework for micropapillary adenocarcinoma detection

PURPOSE

Micropapillary adenocarcinoma is a distinctive histological subtype of lung adenocarcinoma with poor prognosis. Computer-aided diagnosis method has the potential to provide help for its early diagnosis. But the implementation of the existing methods largely relies on massive manually labeled data and consumes a lot of time and energy. To tackle these problems, we propose a framework that applies semi-supervised learning method to detect micropapillary adenocarcinoma, which aims to utilize labeled and unlabeled data better.

METHODS

The framework consists of a teacher model and a student model. The teacher model is first obtained by using the labeled data. Then, it makes predictions on unlabeled data as pseudo-labels for students. Finally, high-quality pseudo-labels are selected and associated with the labeled data to train the student model. During the learning process of the student model, augmentation is added so that the student model generalizes better than the teacher model.

RESULTS

Experiments are conducted on our own whole slide micropapillary lung adenocarcinoma histopathology image dataset and we selected 3527 patches for the experiment. In the supervised learning, our detector achieves a precision of 0.762 and recall of 0.884. In the semi-supervised learning, our method achieves a precision of 0.775 and recall of 0.896; it is superior to other methods.

CONCLUSION

We proposed a semi-supervised learning framework for micropapillary adenocarcinoma detection, which has better performance in utilizing both labeled and unlabeled data. In addition, the detector we designed improves the detection accuracy and speed and achieves promising results in detecting micropapillary adenocarcinoma.

Factors associated with lymph node metastasis upstage after resection for patients with micropapillary lung adenocarcinoma

Background

Micropapillary adenocarcinoma has a poor prognostic histological pattern. Additionally, preoperative detection of lymph node metastases by preoperative examination is difficult in some patients with micropapillary adenocarcinoma, and postoperative upstage may occur. However, clinicopathological features of patients with micropapillary adenocarcinoma with nodal upstage have not been established, therefore this study aimed to identify the factors associated with potential lymph node metastases during preoperative examination to ensure effective surgical procedures.

Methods

Between January 2011 and December 2020, 1029 patients received complete resection for primary non‐small‐cell lung cancer by lobectomy or more extensive resection with systematic lymph node dissection at this institution. One hundred and thirty‐one patients diagnosed with adenocarcinoma with micropapillary component were included in this study. The clinicopathological features of patients with nodal upstage whose postoperative N stage was more advanced than the preoperative N stage were examined.

Results

Forty patients had nodal upstage after resection. ¹⁸F‐fluorodeoxyglucose (FDG) positron emission tomography‐computed tomography (PET‐CT) revealed that a maximum standardized uptake value (SUVmax) ≥5 for the primary lesion was significantly associated with postoperative nodal upstage. There were no significant differences in terms of sex, age, smoking history, surgical procedure, and diabetes. Among 38 patients with nodal upstage, 23 patients had no significant preoperative lymphadenopathy and showed no abnormal FDG uptake in the lymph nodes on ¹⁸F‐FDG‐PET‐CT, respectively.

Conclusions

Lymph node metastases were suspected in patients preoperatively diagnosed with micropapillary adenocarcinoma with FDG SUVmax ≥5 for the primary tumor. Therefore, standard surgical resection and careful lymph node dissection should be performed for such patients.

The nonsmokers' and smokers' pathways in lung adenocarcinoma: Histological progression and molecular bases

There could be two carcinogenetic pathways for lung adenocarcinoma (LADC): the nonsmokers' pathway and the smokers' pathway. This review article describes the two pathways with special reference to potential relationships between histological subtypes, malignant grades, and driver mutations. The lung is composed of two different tissue units, the terminal respiratory unit (TRU) and the central airway compartment (CAC). In the nonsmokers' pathway, LADCs develop from the TRU, and their histological appearances change from lepidic to micropapillary during the progression process. In the smokers' pathway, LADCs develop from either the TRU or the CAC, and their histological appearances vary among cases in the middle of the progression process, but they are likely converged to acinar/solid at the end. On a molecular genetic level, the nonsmokers' pathway is mostly driven by EGFR mutations, whereas in the smokers' pathway, approximately one-quarter of LADCs have KRAS mutations, but the other three-quarters have no known driver mutations. p53 mutations are an important factor triggering the progression of both pathways, with unique molecular alterations associated with each, such as MUC21 expression and chromosome 12p13-21 amplification in the nonsmokers' pathway, and HNF4α expression and TTF1 mutations in the smokers' pathway. However, investigation into the relationship between histological progression and genetic alterations is in its infancy. Tight cooperation between traditional histopathological examinations and recent molecular genetics can provide valuable insight to better understand the nature of LADCs.

Clinical implication of tumour spread through air spaces in pathological stage I lung adenocarcinoma treated with lobectomy

OBJECTIVES

The aim of this study was to evaluate the clinical implication of tumour spread through air spaces (STAS) as a prognostic factor in pathological stage I lung adenocarcinoma treated with lobectomy and to identify related parameters.

METHODS

Medical records of patients who underwent pulmonary lobectomy for stage I (American Joint Committee on Cancers eighth edition) lung adenocarcinomas between 2012 and February 2018 at our institutions were reviewed retrospectively. Patients with minimally invasive adenocarcinomas and tumours ≥3 cm in size were excluded. Included patients were classified into STAS (+) and STAS (-) groups. Clinical implications of STAS and recurrence in patients were investigated.

RESULTS

A total of 109 patients was analysed: 41 (37.6%) in the STAS (+) and 68 (62.4%) in the STAS (-) group. STAS was associated with larger consolidation diameter on chest tomography (≥1.5 cm; P = 0.006) or a higher invasive ratio (≥85%; P = 0.012) and presence of a micropapillary pattern in multivariable analysis (P = 0.003) The recurrence-free survival curve showed statistical difference (P = 0.008) with 3-year survival rates of 73.0% (9 patients) and 96.8% (2 patients) in the STAS (+) and STAS (-) group, respectively. However, no statistical significance was observed in the lung cancer-related survival curve (P = 0.648). The presence of STAS was an independent risk factor for recurrence in multivariable analysis (hazard ratio = 5.9, P = 0.031).

CONCLUSIONS

The presence of STAS could be an important risk factor for recurrence in patients with early-stage invasive lung adenocarcinoma treated with pulmonary lobectomy.

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.

Adenocarcinoma of the lung: from BAC to the future

Adenocarcinoma in situ, minimally invasive adenocarcinoma, lepidic predominant adenocarcinoma and invasive mucinous adenocarcinoma are relatively new classification entities which replace the now retired term, bronchoalveolar carcinoma (BAC). The radiographic appearance of these lesions ranges from pure, ground glass nodules to large, solid masses. A thorough understanding of the new classification is essential to radiologists who work with MDT colleagues to provide accurate staging and treatment. A 2-year review was performed of all surgically resected cases of adenocarcinoma in situ, minimally invasive adenocarcinoma and lepidic predominant adenocarcinoma in our institution. Cases are broken down by age, gender, tumour type and tumour location. A pictorial review is presented to illustrate the radiologic and pathologic features of each entity.

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.

Specific expression of MUC21 in micropapillary elements of lung adenocarcinomas - Implications for the progression of EGFR-mutated lung adenocarcinomas

We investigated the significance of MUC21 in EGFR-mutated lung adenocarcinoma (LADC). Two-hundred forty-one surgically resected LADCs (116 EGFR-mutated and 125 wild-type tumors) were examined for immunohistochemical expression of MUC21 protein. A polyclonal antibody and two monoclonal antibodies (heM21C and heM21D) that bind differentially glycosylated MUC21 epitopes were used, and MUC21 proteins detected by these antibodies were named MUC21P, MUC21C, and MUC21D, respectively. MUC21 mRNA levels were semi-quantified and classified into “high” and “low”. Among the immunohistochemical expression detected by three different antibodies, high expressors tended to be related to EGFR mutations. The three varieties of the immunohistochemical expressions were related to different histological elements in the EGFR-mutated LADCs. Either MUC21P or MUC21C high expressors had a higher proportion of lepidic elements with low papillary structure and micropapillary elements. MUC21D high expressors had a significantly higher proportion of micropapillary elements (Mann-Whitney test P ≤0.0001). Furthermore, MUC21D high expressors showed high incidence of lymphatic canal invasion and lymph node metastasis (Pearson x2 test, P = 0.0021, P = 0.0125), and a significantly higher recurrence rate (5-year recurrence-free survival 50.7% vs. 73.8%, log-rank test P = 0.0495). MUC21 proteins with a specific glycosylation status may be involved in the progression of EGFR-mutated LADCs, particularly at the stage where tumors are transforming from pure lepidic to micropapillary through low papillary lepidic lesions.

The more the micropapillary pattern in stage I lung adenocarcinoma, the worse the prognosis-a retrospective study on digitalized slides

Although the majority of lung adenocarcinomas show mixed pattern, only the predominant component is taken into account according to the novel classification. We evaluated the proportion of different patterns and their impact on overall survival (OS) and disease-free survival (DFS). Patterns were recorded according to predominance and their proportions were rated and calculated by objective area measuring on digitalized, annotated slides of resected stage I lung adenocarcinomas. Spearman's rank correlation, Kaplan-Meier models and the log rank test were used for statistical evaluation. Two hundred forty-three stage I adenocarcinoma were included. Lepidic pattern is more frequent in tumours without recurrence (20 vs. 8%), and lepidic predominant tumours have favourable prognosis (OS 90.5%, DFS 89.4%), but proportions above 25% are not associated with improving outcome. Solid and micropapillary patterns are more frequent in patients with recurrence (48 vs. 5% and 13 vs. 4%) and predominance of each one is associated with unfavourable prognosis (OS 64.1%, DFS 56.3% and OS 28.1%, DFS 28.1%, respectively). Above 25%, a growing proportion of solid or micropapillary pattern is not associated with worsening prognosis. In contrast, tumours having micropapillary pattern as secondly predominant form a different intermediate group (OS 51.1%, DFS 57.8%). Our study was based on measured area of each growth pattern on all available slides digitalized. This is the most precise way of determining the size of each component from the material available. We propose using predominant and secondly predominant patterns for prognostic purposes, particularly in tumours having solid or micropapillary patterns.

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.

A Histopathological Feature of EGFR-Mutated Lung Adenocarcinomas with Highly Malignant Potential - An Implication of Micropapillary Element

The purpose of this study was to define histological features determining the malignant potential of EGFR-mutated lung adenocarcinoma (LADC). Surgically resected tumors (EGFR-mutated LADCs with (21) and without (79) lymph node metastasis and EGFR wild-type LADCs with (26) and without (108) lymph node metastasis) and biopsy samples from inoperably advanced tumors (EGFR-mutated LADCs (78) and EGFR wild-type LADCs (99)) were examined. In surgically resected tumors, the EGFR-mutated LADCs with lymph node metastasis had the micropapillary element in a significantly greater proportion than others (Mann-Whitney tests P ≤0.026). The proportion of micropapillary element was higher in the EGFR-mutated LADC at the advanced stage (stage II, III, or IV) than in the tumor at the early stage (stage I) (Mann-Whitney test, P<0.0001). In the biopsy samples from inoperably advanced LADCs (177), EGFR-mutated tumors also had micropapillary element at a higher frequency than EGFR-wild type tumors (53/78 (68%), versus 30/99 (30%), Pearson x2 test, P<0.0001). In stage I EGFR-mutated LADCs (84), the tumors with the micropapillary element (34) exhibited a significantly higher recurrence rate than tumors without micropapillary element (50) (5-year Recurrence-free survival 64.4% versus 93.3%, log-rank test P = 0.028). The micropapillary element may be an exclusive determinant of malignant potential in EGFR-mutated LADC. It is suggested that EGFR-mutated LADC may develop through a distinct histogenesis, in which the micropapillary element is important for promoting progression.

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.

Is there significance in identification of non-predominant micropapillary or solid components in early-stage lung adenocarcinoma?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was 'in early-stage lung adenocarcinomas, does the presence of non-predominant micropapillary (MIP) or solid (SOL) growth component influence long-term survival and surgical strategy?'. Altogether, more than 600 papers were found using the reported search, of which 13 presented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group, study type, relevant outcomes and results of these papers were tabulated. The data collected showed that non-predominant MIP or SOL components in early-stage lung adenocarcinoma can be up to 60.4 and 41.8%, respectively. MIP or SOL components were associated with significantly reduced period of disease-free or overall survival. One study also showed a higher incidence of occult lymph node metastasis in patients with a minor MIP component. Furthermore, the presence of an MIP/SOL component in early-stage adenocarcinomas (ADCs) could influence the oncological outcome following sublobar resection. We conclude that a non-predominant MIP/SOL pattern is a negative prognostic factor and an indicator of early recurrence after limited resection.

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.

Genetic alterations in lung adenocarcinoma with a micropapillary component

Pulmonary adenocarcinoma (PA) with a micropapillary component (PA-MPC) is known as an aggressive subtype of PA. The molecular profiles of PA-MPC have not been well characterized. the pathological reports of patients who underwent surgical resection for lung cancer between April, 2004 and May, 2012 were reviewed. Of the 674 patients diagnosed with PA, 28 were found to have MPC. A total of 138 resected PAs without MPC were selected in the same period to serve as age-, gender- and smoking status-matched controls to the PA-MPC group. Mutational status was determined by the following two methods: SNaPshot assay based on multiplex polymerase chain reaction (PCR), primer extension and capillary electrophoresis that was designed to assess 38 somatic mutations in 8 genes [AKT1, BRAF, endothelial growth factor receptor (EGFR), Kirsten rat sarcoma viral oncogene homolog (KRAS), mitogen-activated protein kinase kinase 1, neuroblastoma RAS viral oncogene homolog, phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit α (PIK3CA) and phosphatase and tensin homolog]; and a PCR-based sizing assay that assesses EGFR exon 19 (deletions), EGFR exon 20 (insertions) and human epidermal growth factor receptor 2 exon 20 (insertions). echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase fusion gene (EML4-ALK) was screened by ALK immunohistochemistry and confirmed using the reverse transcription PCR assay and the break-apart fluorescence in situ hybridization assay. Regarding genetic alterations, 13 (46.4%) of the 28 PA-MPCs harbored mutually exclusive mutations: 9 (32.1%) EGFR mutations, 1 (3.6%) KRAS mutation and 3 (10.7%) EML4-ALK fusion genes. PAs without MPC harbored 42 (30.4%) EGFR mutations, 17 (12.3%) KRAS mutations, 3 (2.2%) EML4-ALK fusion genes and 1 (0.7%) PIK3CA mutation. EML4-ALK fusion genes appeared to occur significantly more frequently in PA-MPCs compared with PAs without MPC (P=0.027). Although the sample size was small, our study suggests that the molecular pathogenesis of PA-MPC may be different from that of other adenocarcinomas.

Prevalent and up-regulated vimentin expression in micropapillary components of lung adenocarcinomas and its adverse prognostic significance

The factors conferring the increased malignancy on lung adenocarcinoma with micropapillary component (AC-MPC) remain to be elucidated. On proteomics based on 2-dimensional gel electrophoresis, 19 proteins differentially expressed by more than 1.5-fold between AC-MPC and conventional adenocarcinoma (CAC); in particular, vimentin, one of the proteins, was 3.5-fold up-regulated in AC-MPC. Subsequent semi-quantitative investigation by immunohistochemistry with large cohorts comprised 101 AC-MPC and 119 CAC, respectively, of different stages revealed that vimentin was expressed in MPC of 95 (94.1%) AC-MPC and the expression scores were higher than those of well- and moderately differentiated CAC, as well as the background non-MPC of the AC-MPC (P < 0.0001), but not significantly different from those of poorly differentiated CAC (P = 0.561). Even within the AC-MPC entity, higher vimentin expression was correlated with more frequent vascular invasion and more advanced node metastasis (P < 0.02), and multivariate analysis showed that high vimentin expression and worse node statuses were independent indicators of adverse prognosis (P < 0.048). In conclusion, vimentin expression is prevalent and markedly up-regulated in MPC, which might reflect the biological essence of poorer differentiation or dedifferentiation of MPC, and this might have a role in the acquisition and increase of invasiveness and consequent more malignant nature of MPC.

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.

Clinical and pathologic prognostic factors that are influential in the survival and prognosis of lung adenocarcinomas and invasive predominant subtypes

Therapeutic approaches to lung adenocarcinomas differ because of their heterogeneous morphologies, prognoses, and clinical features. For this reason, new histopathologic classifications for lung adenocarcinomas were done by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society to form subtypes with homogeneous prognoses. There are limited clinical data in the literature on the prognosis of the subgroups formed according to the new classification. A total of 86 patients with adenocarcinoma who had undergone pathologic stages I and II curative resection and mediastinal lymph node dissection were retrospectively analyzed according to the seventh TNM staging system revised by the Union for International Cancer Control/American Joint Committee on Cancer. Histologic subtyping was reassessed according to the dominant histopathologic morphology. When survival rates of lung adenocarcinomas were compared according to their localizations, it was observed that adenocarcinomas localized to the right hemithorax had a longer survival than the ones with left hemithorax localization (P = 0.026). When necrosis was taken into account, it was seen that necrosis rate was higher in solid predominant type compared with other types, whereas it was lower in acinary type (P = 0.046). When peritumoral lymphovascular invasion data were assessed, it was observed that disease-free survival was influenced in a negative fashion (P = 0.018). New histopathologic classification of adenocarcinomas has been a step forward to attaining homogeneous groups, but when the biologic heterogeneity of the adenocarcinomas is taken into account, the authors believe that considering the peritumoral lymphatic vascular invasion, left hemithorax localization, and tumoral necrosis entities in the upcoming TNM classification will contribute to evaluating the prognosis.

The new IASLC-ATS-ERS lung adenocarcinoma classification: what the surgeon should know

In 2011, a new histologic classification of lung adenocarcinomas was proposed from a joint working group of the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society, based on the recommendation of an international and multidisciplinary panel. This classification proposed a method of comprehensive histologic subtyping (lepidic, acinar, papillary, micropapillary, and solid pattern) based on semiquantitative assessment of histologic patterns (in 5% increments), with the ultimate goal of choosing a single, predominant pattern. Prognostic subsets could then be described for the classification. Patients with completely resected adenocarcinoma in situ and minimally invasive adenocarcinomas experienced low risk of recurrence. Patients with micropapillary or solid predominant tumors have a high risk of recurrence or cancer-related death. Patients with acinar and papillary predominant tumors comprise an intermediate-risk group. Herein, we review the outline of the proposed International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society classification, a summary of published validation studies of this new classification, and then discuss the key surgical issues; we mainly focused on limited resection as an adequate treatment for early-stage lung adenocarcinomas, as well as preoperative and intraoperative diagnoses. We also review the published studies that identified the importance of histologic subtypes in predicting recurrence, both rates and patterns, in early-stage lung adenocarcinomas. This new classification for the most common type of lung cancer is useful for surgeons, as its implementation would require only hematoxylin-and-eosin histology slides, which is the common type of stain used in hospitals. It can be implemented with routine pathology evaluation and with no additional costs.

Invasive micropapillary carcinoma of the extrahepatic bile duct and its malignant potential

Invasive micropapillary carcinoma (IMPC) was originally described as a distinctive type of invasive carcinoma in the breast, but it has not been recognized as a histological type of the extrahepatic bile duct cancer. The present study demonstrated clinicopathological features and patient prognosis of IMPC. We examined histological reviews of 93 consecutive cases of the extrahepatic bile duct cancer and identified 13 cases which included IMPC component. The component of IMPC ranged from 5 to 60% of the primary tumor tissue, which was mainly detected at the invasive front of the tumor. Of the 13 cases, 12 (92.3%) carcinomas with IMPC showed lymph node metastasis more frequently compared to conventional adenocarcinoma (39.2%, P<0.001). Presence of IMPC component was significantly associated with poor overall survival (P=0.003). In conclusion, extrahepatic bile duct carcinoma with IMPC component showed significant lymphatic invasion, lymph node metastasis, and resulted in poor prognosis.

Recent advances and clinical implications of the micropapillary histological subtype in lung adenocarcinomas

Micropapillary (MIP) histologic subtype included in the classification of lung adenocarcinomas (ADCs) is associated with both size- and stage-independent poor prognoses. MIP pattern in lung ADCs, even at small, early stages, correlates with high lymphovascular invasion, visceral pleural invasion and lymph node metastases. Recently, we reported that patients with a MIP component are at a higher risk of locoregional recurrence after limited resection. Identification of a MIP pattern is only possible with permanent pathologic sections; preoperative imaging, cytology or intraoperative frozen section specimens remain unreliable. The intermixed, heterogenous morphology of lung ADC presents a technical challenge in investigating the molecular biology of cells with MIP morphology. A comprehensive understanding of the biology of MIP morphology is vital for therapeutic interventions.

Extraction bag lavage cytology during video-assisted thoracoscopic surgery for primary lung cancer

OBJECTIVES

Sample extraction from the thoracic cavity through an intercostal space during video-assisted thoracoscopic surgery can result in cancer cell contamination by tumour crushing and tumour cell extravasation, and may have adverse effects on the surgical outcome. Lavage cytology of the sample extraction bag was investigated to clarify the risk of cancer cell spillage and identify the clinicopathological features associated with susceptibility to cancer cell spillage during extraction.

METHODS

Lavage cytology of the sample extraction bag was investigated in 464 patients with negative pleural lavage cytology who underwent lung resection for primary lung cancer via video-assisted thoracoscopic surgery between January 2010 and December 2012. The surgical procedures, pathological findings and clinical course were evaluated by hospital record review.

RESULTS

The incidence of positive bag lavage cytology (BLC) was 13.6%. Statistically significant factors associated with susceptibility to BLC positivity were tumour size, standardized uptake value of positron emission tomography, pathological features such as pathological N score, pleural invasion, vascular invasion and papillary-predominant adenocarcinoma. Among patients with Stage I lung cancer, the survival rate was significantly lower in the BLC-positive group than in the BLC-negative group.

CONCLUSIONS

BLC positivity can be related to oncological characteristics such as tumour invasiveness and adhesiveness as opposed to tumour size and surgical margin, and may help to determine the prognosis of Stage I lung cancer. The sample extraction bag must be carefully manoeuvred through the intercostal space to prevent cancer cell dissemination to the chest wall or thoracic cavity.

Association of c-Met phosphorylation with micropapillary pattern and small cluster invasion in pT1-size lung adenocarcinoma

Lung adenocarcinomas with micropapillary pattern (MPP) are associated with frequent nodal metastasis. However, little is known about the mechanisms that underlie MPP-associated nodal metastasis. We have previously reported that pT1 lung adenocarcinomas with MPP are significantly associated with small cluster invasion (SCI) and lymphatic involvement. SCI is defined as markedly resolved acinar-papillary tumor structures with single or small clusters of carcinoma cells invading stroma within fibrotic foci. In this study, we hypothesized that c-Met activation may be involved in the MPP-SCI sequence, given that the c-Met tyrosine-kinase receptor and its ligand hepatocyte growth factor (HGF), play important roles in tumor cell motility and invasion. We analyzed 125 pT1-size lung adenocarcinomas for immunohistochemical expression of phosphorylated c-Met and its correlation with MPP, SCI, lymphatic involvement and prognosis. SCI was significantly more frequent in the MPP-positive group (P<0.0001) and associated with lymphatic involvement (P<0.0001) and nodal metastasis (P=0.021). c-Met protein was detected in all tumors by immunohistochemistry as membranous and cytoplasmic staining. Phospho-c-Met (pc-Met) was positive in 119/125 tumors (95%) and expressed at high levels in 27 cases (22%). A high level of pc-Met expression was significantly associated with MPP (P=0.01) and SCI (P=0.0059). Moreover, in tumors with MPP or SCI, those expressing high levels of pc-Met were significantly more associated with lymphatic involvement. In p-Stage IA lung adenocarcinomas (n=99), patients in the high pc-Met expression group showed significantly worse survival than patient in the low expression group (P=0.0313). These results suggest that activation of c-Met through phosphorylation may be involved in MPP and SCI.

Correlation of mutation status and survival with predominant histologic subtype according to the new IASLC/ATS/ERS lung adenocarcinoma classification in stage III (N2) patients

INTRODUCTION

We investigated the relationship between predominant subtype, according to the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society International Multidisciplinary Lung Adenocarcinoma Classification; mutation status; and patient outcome in stage III (N2) lung adenocarcinoma.

METHODS

We identified 69 patients with stage III (N2) lung adenocarcinoma operated on with curative intent between 1993 and 2011 who had adequate tumor tissue for molecular analysis and adequate follow-up time for survival analysis. DNA was isolated and tested for mutations using Sequenom's OncoCarta Panel (v1.0; Sequenom, San Diego, CA).

RESULTS

The majority of tumors were acinar (26 of 69 tumors; 38%), solid (24 of 69 tumors; 35%), and micropapillary predominant (13 of 69 tumors; 19%) subtypes. EGFR and KRAS mutations were identified in 17 of 59 tumors (29%) and 13 of 59 tumors (22%), respectively. EGFR mutations occurred most often in acinar (11 of 25 tumors; 44%) and micropapillary predominant tumors (five of 13 tumors; 38%) (p = 0.009), whereas KRAS mutations occurred most often in solid predominant tumors (nine of 21 tumors; 43%) (p = 0.016). Patients with acinar predominant tumors had significantly improved overall survival compared with those with non-acinar predominant tumors (hazard ratio: 0.45; 95% confidence interval: 0.22-0.91; p = 0.026), which remained significant after adjustment for EGFR status, T-stage, sex, and age. Patients with EGFR-mutant micropapillary predominant tumors had similar survival to those with EGFR-mutant acinar predominant tumors. The predominant subtype in the primary tumor was most often seen in the N2 node in micropapillary and solid predominant tumors but not in acinar predominant tumors.

CONCLUSIONS

The predominant subtype in the primary tumor was associated with overall survival in resected stage III (N2) lung adenocarcinoma and was independent of mutation status. Histologic subtyping provides important prognostic information and potentially molecular correlates.

Impact of micropapillary histologic subtype in selecting limited resection vs lobectomy for lung adenocarcinoma of 2cm or smaller

BACKGROUND

We sought to analyze the prognostic significance of the new International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) lung adenocarcinoma (ADC) classification for patients undergoing resection for small (≤2cm) lung ADC and to investigate whether histologic subtyping can predict recurrence after limited resection (LR) vs lobectomy (LO).

METHODS

Comprehensive histologic subtyping was performed according to the IASLC/ATS/ERS classification on all consecutive patients who underwent LR or LO for small lung ADC between 1995 and 2009 at Memorial Sloan-Kettering Cancer Center. Clinical characteristics and pathologic data were retrospectively evaluated for 734 consecutive patients (LR: 258; LO: 476). Cumulative incidence of recurrence (CIR) was calculated using competing risks analysis and compared across groups using Grey's test. All statistical tests were two-sided.

RESULTS

Application of IASLC/ATS/ERS lung ADC histologic subtyping to predict recurrence demonstrates that, in the LR group but not in the LO group, micropapillary (MIP) component of 5% or greater was associated with an increased risk of recurrence, compared with MIP component of less than 5% (LR: 5-year CIR = 34.2%, 95% confidence interval [CI] = 23.5% to 49.7% vs 5-year CIR = 12.4%, 95% CI = 6.9% to 22.1%, P < .001; LO: 5-year CIR = 19.1%, 95% CI = 12.0% to 30.5% vs 15-year CIR = 12.9%, 95% CI = 7.6% to 21.9%, P = .13). In the LR group, among patients with tumors with an MIP component of 5% or greater, most recurrences (63.4%) were locoregional; MIP component of 5% or greater was statistically significantly associated with increased risk of local recurrence when the surgical margin was less than 1cm (5-year CIR = 32.0%, 95% CI = 18.6% to 46.0% for MIP ≥ 5% vs 5-year CIR = 7.6%, 95% CI = 2.3% to 15.6% for MIP < 5%; P = .007) but not when surgical margin was 1cm or greater (5-year CIR = 13.0%, 95% CI = 4.1% to 22.1% for MIP ≥ 5% vs 5-year CIR = 3.4%, 95% CI = 0% to 7.7% for MIP < 5%; P = .10).

CONCLUSIONS

Application of the IASLC/ATS/ERS classification identifies the presence of an MIP component of 5% or greater as independently associated with the risk of recurrence in patients treated with LR.

Diagnosis of lung adenocarcinoma in resected specimens: implications of the 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification

A new lung adenocarcinoma classification has been published by the International Association for the Study of Lung Cancer, the American Thoracic Society, and the European Respiratory Society. This new classification is needed to provide uniform terminology and diagnostic criteria, most especially for bronchioloalveolar carcinoma. It was developed by an international core panel of experts representing all 3 societies with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons.This summary focuses on the aspects of this classification that address resection specimens. The terms bronchioloalveolar carcinoma and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced, such as adenocarcinoma in situ and minimally invasive adenocarcinoma for small solitary adenocarcinomas with either pure lepidic growth (adenocarcinoma in situ) and predominant lepidic growth with invasion of 5 mm or less (minimally invasive adenocarcinoma), to define the condition of patients who will have 100% or near 100% disease-specific survival, respectively, if they undergo complete lesion resection. Adenocarcinoma in situ and minimally invasive adenocarcinoma are usually nonmucinous, but rarely may be mucinous. Invasive adenocarcinomas are now classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous bronchioloalveolar carcinoma), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous bronchioloalveolar carcinoma), colloid, fetal, and enteric adenocarcinoma.It is possible that this classification may impact the next revision of the TNM staging classification, with adjustment of the size T factor according to only the invasive component pathologically in adenocarcinomas with lepidic areas.

Expression of CLDN1 and CLDN10 in lung adenocarcinoma in situ and invasive lepidic predominant adenocarcinoma

Background

Non-mucinous bronchioloalveolar carcinoma (BAC) is considered the early stage of lung adenocarcinoma and is classified as the lung adenocarcioma in situ (AIS) by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society. This study was designed to investigate the gene expression differences between AIS (formerly non–mucinous BAC) and invasive lepidic predominant adenocarcinoma (LPA, formerly non-mucinous BAC pattern with >5 mm invasion, mixed type adenocarcinoma with BAC features) and to investigate the mechanism of the progression of lung adenocarcinoma in situ to invasive adenocarcinoma.

Methods

Gene expression analysis was performed by using Agilent 4 × 44 K Whole Human Genome Oligo Microarray on 10 fresh frozen tissue samples of AIS and LPA, respectively. Real time RT-PCR was used to validate the differential expression of 13 genes selected by cDNA microarray on fresh frozen tissue samples from 41 patients with lung adenocarcinoma and 4 genes were confirmed. These 4 genes were then validated by western blotting. Immunohistochemical staining for these validated genes was performed on formalin-fixed, paraffin-embedded tissue samples from 81 cases of lung adenocarcinomna.

Results

We identified a 13 gene expression signature by comparative analysis of gene expression. Expression of these genes strongly differed between AIS and LPA. Four genes (MMP-2, c-fos, claudin 1 (CLDN1) and claudin 10(CLDN10)) were correlated with the results of microarray and real time RT-PCR analyses for the gene-expression data in samples from 41 patients with lung adenocarcinoma. As confirmed by western blotting, the expression levels of MMP-2 and c-fos were higher in LPA than those in AIS; the expression levels of CLDN1 and CLDN10 in LPA were lower than those in AIS. Immunohistochemical staining for these genes in samples from 81 cases of lung adenocarcinoma demonstrated the expressions of CLDN1 and CLDN10 were correlated with overall survival of patients with lung adenocarcinoma.

Conclusions

CLDN1 and CLDN10 may play important roles in the development of AIS to LPA. Overexpression of CLDN1 and CLDN10 indicates a favorable prognosis for overall survival in some patients with lung adenocarcinoma. Expression of CLDN10 may be regulated by the c-fos pathway.

Clinical relevance of the new IASLC/ERS/ATS adenocarcinoma classification

In 2011, recommendations for a multidisciplinary classification of lung adenocarcinoma were published under the auspices of the International Association for the Study of Lung Cancer, the American Thoracic Society and the European Respiratory Society. The review was considered necessary due to emerging data on the radiological features, genetics and therapeutic approaches to lung adenocarcinoma, all underpinned by expanding the knowledge of the pathology of this common tumour. The existing WHO classification of 2004 was not really fit for this multidisciplinary focus on the disease. This review describes the recommendations made on the reporting of surgically resected lung cancers according to their predominant pattern, and argues the case for replacing the term bronchioloalveolar carcinoma (WHO 1999 and 2004 definition) with adenocarcinoma in situ and for the introduction of minimally invasive adenocarcinoma. There is also a discussion of diagnosis of non-small-cell lung carcinomas in the small biopsy or cytology setting, a practice that was inadequately addressed in WHO 2004, yet this is much more relevant to most pathologists' daily practice because 85% or so of adenocarcinomas are never resected. Predictive immunohistochemistry, used correctly, can reduce non-specific diagnosis to less than 10% of the cases. Finally, there is an overview of the emerging data on therapeutically relevant lung adenocarcinoma genetics, considering targetable mutations that are now the focus of much activity. The clinical relevance of these changes is discussed.

Tumor islands in resected early-stage lung adenocarcinomas are associated with unique clinicopathologic and molecular characteristics and worse prognosis

Tumor islands-large collections of tumor cells isolated within alveolar spaces-can be seen in lung adenocarcinomas. Recently we observed by 3-dimensional reconstruction that these structures were connected with each other and with the main tumor in different tissue planes, raising the possibility of tumor islands being a means of extension. However, the clinical and prognostic significance of tumor islands remains unknown. In this study, we compared clinicopathologic and molecular characteristics and prognosis of stages I to II lung adenocarcinomas with tumor islands (n=58) and those without (n=203). Lung adenocarcinomas with tumor islands were more likely to occur in smokers, exhibit higher nuclear grade and a solid or micropapillary pattern of growth, and harbor KRAS mutations. In contrast, lung adenocarcinomas without tumor islands were more likely to present as minimally invasive adenocarcinoma, show a lepidic pattern of growth, and harbor EGFR mutations. Although there was no difference in stage, the prognosis of lung adenocarcinomas with tumor islands was significantly worse than those without. The 5-year recurrence-free survival for patients with tumor islands and those without was 44.6% and 74.4%, respectively (log rank P=0.010). The survival difference remained significant (P <0.020) by multivariate analysis, and the presence of tumor islands was associated with almost 2-fold increase in the risk of recurrence. Even in the stage IA cohort, more than half of the patients with tumor islands experienced recurrence within 5 years. Thus, aggressive surveillance and/or further intervention may be indicated for patients whose tumors exhibit tumor islands.

Radiologic implications of the 2011 classification of adenocarcinoma of the lung

Now the leading subtype of lung cancer, adenocarcinoma received a new classification in 2011. For tumors categorized previously as bronchioloalveolar carcinoma (BAC), criteria and terminology had not been uniform, so the 2011 classification provided four new terms: (a) adenocarcinoma in situ (AIS), representing histopathologically a small (≤3-cm), noninvasive lepidic growth, which at computed tomography (CT) is usually nonsolid; (b) minimally invasive adenocarcinoma, representing histopathologically a small (≤3-cm) and predominantly lepidic growth that has 5-mm or smaller invasion, which at CT is mainly nonsolid but may have a central solid component of up to approximately 5 mm; (c) lepidic predominant nonmucinous adenocarcinoma, representing histopathologically invasive adenocarcinoma that shows predominantly lepidic nonmucinous growth, which at CT is usually part solid but may be nonsolid or occasionally have cystic components; and (d) invasive mucinous adenocarcinoma, histopathologically showing lepidic growth as its predominant component, which at CT varies widely from solid to mostly solid to part solid to nonsolid and may be single or multiple (when multifocal, it was formerly called multicentric BAC). In addition, new histopathologic subcategories of acinar, papillary, micropapillary, and solid predominant adenocarcinoma are now described, all as nonmucinous, predominantly invasive, may include a small lepidic component, and at CT are usually solid but may include a small nonsolid component. The micropapillary subtype has a poorer prognosis than the other subtypes. In addition, molecular genetic correlations for the subcategories of adenocarcinoma of the lung are now a topic of increasing interest. As the new classification enters common use, further descriptions of related correlations can be anticipated.

Solitary pulmonary nodular lung adenocarcinoma: correlation of histopathologic scoring and patient survival with imaging biomarkers

PURPOSE

To evaluate the usefulness of histopathologic scoring for survival prediction in patients with solitary pulmonary nodular (SPN) lung adenocarcinomas and to correlate the histopathologic scoring with the results of computed tomography (CT) and fluorine 18 fluorodeoxyglucose positron emission tomography (PET)/CT.

MATERIALS AND METHODS

This retrospective study was institutional review board approved and the requirement for informed consent was waived. A total of 148 patients with SPN lung adenocarcinoma underwent PET/CT and CT. Correlations between histopathologic scores estimated by using two predominant histologic subtypes from each surgically resected specimen and the mass of the nodule at CT or maximum standardized uptake value (SUV(max)) at PET/CT were assessed. Disease-free survival (DFS) was estimated by using the Kaplan-Meier method, and the log-rank test was used to evaluate differences in each histopathologic subtype.

RESULTS

In 135 (91%) patients, tumors had a mixed subtype. The most frequently observed histologic subtypes, in decreasing order, were acinar (51%), lepidic (18%), solid (10%), and papillary (9%). DFS rates at 5 years were higher than 90% for the group of patients with nodules that showed the lepidic growth pattern, and 50% for patients with nodules that showed the micropapillary pattern. The pathologic score proved to be a significant predictor of DFS (P < .001). Both SUV(max) and the mass of the nodule were closely correlated with pathologic score.

CONCLUSION

Pathologic scoring appears to help predict DFS in patients with SPN lung adenocarcinoma and shows close correlation with imaging biomarkers including the mass of the nodule at CT and SUV(max) at PET/CT.

Clinicopathological characteristics of subcentimeter adenocarcinomas of the lung

BACKGROUND

Identification of subcentimeter adenocarcinoma is becoming easier due to recent advances in radiographic techniques. Pathological (p) T1a (≤20 mm) adenocarcinomas with a pure lepidic growth pattern have excellent prognosis, whereas invasive pT1a adenocarcinomas are associated with recurrence/metastasis despite their small size. Thus, an accurate pathological diagnosis is critical in such cases. This study examined the clinicopathological characteristics of subcentimeter adenocarcinomas, especially those associated with early invasive carcinomas.

METHODS

We retrospectively reviewed 595 adenocarcinomas including 66 subcentimeter carcinomas, which were then analyzed with reference to early invasive features.

RESULTS

Of the 66 subcentimeter tumors, 36 were invasive and 30 were noninvasive (adenocarcinoma in situ, AIS). Invasive carcinomas were significantly more frequent in males than females, and included 20 tumors with ≤5 mm invasion in greatest dimension (minimally invasive adenocarcinoma, MIA) and 16 tumors with >5mm invasion, 5 of which had no lepidic growth portions (entirely invasive carcinoma). Approximately half of the invasive carcinomas had no localized fibrous area ≥1 mm in diameter (LFA), and showed histological features of invasive carcinoma with localized lepidic growth including MIA (Noguchi's type C). Invasion was sometimes difficult to detect in these carcinomas. High-grade nuclear atypia was always associated with invasive carcinomas and aided the diagnosis. Moreover, invasive carcinoma with >5mm invasion was significantly associated with presence of metastasis in sensitivity analysis in patients followed for more than two years. Compared with adenocarcinomas of 11-20mm in diameter, subcentimeter carcinomas included significantly more AIS, fewer entirely invasive carcinomas, and fewer invasive carcinomas with LFA.

CONCLUSIONS

Familiarity with the histopathological characteristics of subcentimeter adenocarcinomas as described above could aid the accurate diagnosis of early invasive carcinomas.

Neoadjuvant erlotinib and surgical resection of a stage iiia papillary adenocarcinoma of the lung with an L861Q activating EGFR mutation

The use of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is evolving, as is an understanding of predictive biomarkers for tumour response in non-small-cell lung cancer (NSCLC). In this report, we describe a case of rapidly progressing, borderline-resectable, clinical stage IIIA (micro) papillary adenocarcinoma in a 78-year-old woman who experienced a profound response to neoadjuvant erlotinib without short-term toxicity. On EGFR mutation testing, this patient had an uncommon activating point mutation at L861Q in exon 21. Her response permitted successful surgical resection with negative margins and avoidance of chemoradiation, which she was deemed too frail to tolerate. Our case addresses unique management issues such as preoperative testing for EGFR mutation, utility of histology in predicting EGFR mutations, and use of EGFR-TKIs pre- and postoperatively for potentially resectable NSCLC.

Non-small-cell lung cancer

In the decade since the last Lancet Seminar on lung cancer there have been advances in many aspects of the classification, diagnosis, and treatment of non-small-cell lung cancer (NSCLC). An international panel of experts has been brought together to focus on changes in the epidemiology and pathological classification of NSCLC, the role of CT screening and other techniques that could allow earlier diagnosis and more effective treatment of the disease, and the recently introduced seventh edition of the TNM classification and its relation to other prognostic factors such as biological markers. We also describe advances in treatment that have seen the introduction of a new generation of chemotherapy agents, a proven advantage to adjuvant chemotherapy after complete resection for specific stage groups, new techniques for the planning and administration of radiotherapy, and new surgical approaches to assess and reduce the risks of surgical treatment.

Histologic patterns and molecular characteristics of lung adenocarcinoma associated with clinical outcome

BACKGROUND

Lung adenocarcinoma is histologically heterogeneous and has 5 distinct histologic growth patterns: lepidic, acinar, papillary, micropapillary, and solid. To date, there is no consensus regarding the clinical utility of these patterns.

METHODS

The authors performed a detailed semiquantitative assessment of histologic patterns of 240 lung adenocarcinomas and determined the association with patients' clinicopathologic features, including recurrence-free survival (RFS) and overall survival (OS) rates. In a subset of tumors, expression levels of 2 prognostic molecular markers were evaluated: thyroid transcription factor-1 (TTF-1) (n = 218) and a panel of 5 proteins (referred as the FILM signature index) (n = 185).

RESULTS

Four mutually exclusive tumor histology pattern groups were identified: 1) any solid (38%), 2) any papillary but no solid (14%), 3) lepidic and acinar but no solid or papillary (30%), and 4) acinar only (18%). Patients in group 3 had a higher RFS rate than patients in group 1 (hazard ratio [HR], 0.4510; P = .0165) and group 2 (HR, 0.4253; P = .0425). Solid pattern tumors (group 1) were associated with a lower OS rate than nonsolid pattern tumors (all stages: HR; 1.665; P = .0144; stages I and II: HR, 2.157; P = .008). In the patients who had tumors with a nonsolid pattern, high TTF-1 expression was associated significantly with higher RFS (HR, 0.994; P = .0017) and OS (HR, 0.996; P = .0276) rates in all stages, and a high FILM signature index score was associated with lower RFS and OS rates in all stages (RFS: HR, 1.343; P = .0192; OS: HR, 1.371; P = .0156) and in stages I and II (RFS: HR, 1.419; P = .0095; OS: HR, 1.315; P = .0422).

CONCLUSIONS

The presence of a solid histologic pattern was identified as a marker of unfavorable prognosis in patients with primary lung adenocarcinoma. High TTF-1 expression and low FILM signature index scores were associated with a better prognosis for patients who had tumors with a nonsolid pattern.

Histopathologic Characteristics of Lung Adenocarcinomas With Epidermal Growth Factor Receptor Mutations in the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society Lung Adenocarcinoma Classification

Context.—The proposed International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification of lung adenocarcinomas has been published.

Objective.—To evaluate the correlation between epidermal growth factor receptor mutations and histologic subtypes of lung adenocarcinomas according to the upcoming new classification of lung adenocarcinomas.

Design.—Medical records and pathologic slides were reviewed for a total of 107 surgically resected lung adenocarcinomas. All tumors were reclassified according to the predominant histologic subtype, and comprehensive histologic subtyping with semiquantitative assessment of each of the histologic subtypes in increments of 5% was performed. Correlations with epidermal growth factor receptor status were then evaluated.

Results.—Epidermal growth factor receptor mutations were found in 54 cases (50.5%). Epidermal growth factor receptor mutations were significantly associated with the micropapillary-predominant subtype (P  =  .02) and with the presence (any amount) of the lepidic component (P  =  .02).

Conclusion.—The upcoming International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification of lung adenocarcinoma is relevant in that it shows a phenotype-genotype correlation. Comprehensive histologic subtyping should be recommended because of the association of particular subtypes with epidermal growth factor receptor mutations.