Prognostic analysis of pulmonary adenocarcinoma subclassification with special consideration of papillary and bronchioloalveolar types

Endobronchial spread of adenocarcinoma is a distinct pattern of invasion and associated with inferior clinical outcomes in lung adenocarcinoma

AIM

The spread of lung adenocarcinoma cells into the bronchi and bronchioles is not well documented. We termed this histological finding "endobronchial spreading of adenocarcinoma" (EBSA) and investigated its prevalence and clinical significance.

METHODS AND RESULTS

We reviewed 320 resected specimens from patients diagnosed with invasive adenocarcinoma, and EBSA was observed in 144 patients (45%). EBSA was significantly associated with advanced pathological stage, higher histological grade, larger tumour invasion, lymphovascular infiltration, and spread through air spaces. Patients with EBSA had significantly shorter relapse-free survival (RFS) and cancer-specific survival (CSS) in univariate analysis (P < 0.001). In a subgroup analysis of patient with small-sized (invasion size ≤30 mm) adenocarcinoma in the localized stage, EBSA was an independent inferior prognostic indicator in multivariate analysis. In a subgroup analysis of patients with small-sized Grade 1 nonmucinous adenocarcinoma (n = 61), EBSA was observed in 11 patients, and the presence of EBSA was associated with significantly shorter RFS and CSS (P = 0.026 and P = 0.001, respectively).

CONCLUSION

Our results demonstrated that EBSA is a significant risk factor for disease recurrence and cancer-related deaths. EBSA can be regarded as a distinctive pattern of invasion and its recognition can be beneficial in the diagnosis of lung adenocarcinoma.

Prediction of lung papillary adenocarcinoma-specific survival using ensemble machine learning models

Accurate prognostic prediction is crucial for treatment decision-making in lung papillary adenocarcinoma (LPADC). The aim of this study was to predict cancer-specific survival in LPADC using ensemble machine learning and classical Cox regression models. Moreover, models were evaluated to provide recommendations based on quantitative data for personalized treatment of LPADC. Data of patients diagnosed with LPADC (2004-2018) were extracted from the Surveillance, Epidemiology, and End Results database. The set of samples was randomly divided into the training and validation sets at a ratio of 7:3. Three ensemble models were selected, namely gradient boosting survival (GBS), random survival forest (RSF), and extra survival trees (EST). In addition, Cox proportional hazards (CoxPH) regression was used to construct the prognostic models. The Harrell's concordance index (C-index), integrated Brier score (IBS), and area under the time-dependent receiver operating characteristic curve (time-dependent AUC) were used to evaluate the performance of the predictive models. A user-friendly web access panel was provided to easily evaluate the model for the prediction of survival and treatment recommendations. A total of 3615 patients were randomly divided into the training and validation cohorts (n = 2530 and 1085, respectively). The extra survival trees, RSF, GBS, and CoxPH models showed good discriminative ability and calibration in both the training and validation cohorts (mean of time-dependent AUC: > 0.84 and > 0.82; C-index: > 0.79 and > 0.77; IBS: < 0.16 and < 0.17, respectively). The RSF and GBS models were more consistent than the CoxPH model in predicting long-term survival. We implemented the developed models as web applications for deployment into clinical practice (accessible through https://shinyshine-820-lpaprediction-model-z3ubbu.streamlit.app/ ). All four prognostic models showed good discriminative ability and calibration. The RSF and GBS models exhibited the highest effectiveness among all models in predicting the long-term cancer-specific survival of patients with LPADC. This approach may facilitate the development of personalized treatment plans and prediction of prognosis for LPADC.

The Characteristics and Nomogram for Primary Lung Papillary Adenocarcinoma

Background

Primary pulmonary papillary adenocarcinoma (PA) is a specific and rare subtype of invasive pulmonary adenocarcinoma (ADC). The knowledge concerning the clinicopathologic features and prognosis of patients with primary pulmonary PA has not been clarified because of its rarity.

Methods

The clinical data of a total of 3391 patients with primary pulmonary PA were retrospectively analyzed to confirm their clinical characteristics and factors influencing prognosis and were in comparison with 3236 patients with non- PA pulmonary adenocarcinoma. All patients were histologically diagnosed between 1988 and 2015 in The Surveillance Epidemiology and End Results (SEER) database. A nomogram with satisfactory predictive performance was established to visually predict long-term survival of these patients.

Results and conclusion

Collectively, primary pulmonary PA is a rare pathological cancer and its prognosis is analogous to that of non-PA pulmonary adenocarcinoma. Older age, larger lesions, distant metastases, lymph node invasion, and poor pathological differentiation are correlative with unacceptable prognosis. Surgical intervention is conducive to reaping favorable prognosis. Unfortunately, radiotherapy or chemotherapy results of no significant effects on patient survival. In our study, a nomogram with prognostic function is formulated to confer individual prediction of overall survival (OS).

Papillary predominant histological subtype predicts poor survival in lung adenocarcinoma

BACKGROUND

This study aims to investigate whether papillary predominant histological subtype can predict poor survival in lung adenocarcinoma.

METHODS

Between January 2005 and December 2016, a total of 80 patients with papillary predominant subtype lung adenocarcinoma (70 males, 10 females; mean age 60.7 years; range, 42 to 79 years) operated in our clinic were included in the study. These patients were compared with those having lepidic, acinar, and mucinous subtypes. Overall and five-year survival rates were evaluated.

RESULTS

Five-year survival was 40.5% in papillary predominant histological subtype, while this rate was 70.9%, 59.0%, and 66.6% in lepidic, acinar, and mucinous subtypes, respectively. Papillary subtype showed significantly poor survival compared to lepidic (p=0.002), acinar (p=0.008), and mucinous subtypes (p=0.048). In Stage 1 disease, it was more evident (papillary, 47.5%, lepidic 86.9% [p=0.001], acinar 69.3% [p=0.040], and mucinous 90.0% [p=0.050]).

CONCLUSION

Our study results suggest that papillary predominant subtype predicts poor survival in lung adenocarcinoma and these cases may be candidates for adjuvant treatment modalities even in the earlier stages of disease.

Radiologic Predictors for Clinical Stage IA Lung Adenocarcinoma with Ground Glass Components: A Multi-Center Study of Long-Term Outcomes

Objective

This study was to define preoperative predictors from radiologic findings for the pathologic risk groups based on long-term surgical outcomes, in the aim to help guide individualized patient management.

Methods

We retrospectively reviewed 321 consecutive patients with clinical stage IA lung adenocarcinoma with ground glass component on computed tomography (CT) scanning. Pathologic diagnosis for resection specimens was based on the 2011 IASLC/ATS/ERS classification of lung adenocarcinoma. Patients were classified into different pathologic risk grading groups based on their lymph node status, local regional recurrence and overall survival. Radiologic characteristics of the pulmonary nodules were re-evaluated by reconstructed three-dimension CT (3D-CT). Univariate and multivariate analysis identifies independent radiologic predictors from tumor diameter, total volume (TV), average CT value (AVG), and solid-to-tumor (S/T) ratio. Receiver operating characteristic curves (ROC) studies were carried out to determine the cutoff value(s) for the predictor(s). Univariate cox regression model was used to determine the clinical significance of the above findings.

Results

A total of 321 patients with clinical stage IA lung adenocarcinoma with ground glass components were included in our study. Patients were classified into two pathologic low- and high- risk groups based on their distinguished surgical outcomes. A total of 134 patients fell into the low-risk group. Univariate and multivariate analyses identified AVG (HR: 32.210, 95% CI: 3.020–79.689, P<0.001) and S/T ratio (HR: 12.212, 95% CI: 5.441–27.408, P<0.001) as independent predictors for pathologic risk grading. ROC curves studies suggested the optimal cut-off values for AVG and S/T ratio were-198 (area under the curve [AUC] 0.921), 2.9 (AUC 0.996) and 54% (AUC 0.907), respectively. The tumor diameter and TV were excluded for the low AUCs (0.778 and 0.767). Both the cutoff values of AVG and S/T ratio were correlated with pathologic risk classification (p<0.001). Univariate Cox regression model identified clinical risk classification (RR: 3.011, 95%CI: 0.796–7.882, P = 0.095) as a good predictor for recurrence-free survival (RFS) in patients with clinical stage IA lung adenocarcinoma. Statistical significance of 5-year OS and RFS was noted among clinical low-, moderate- and high-risk groups (log-rank, p = 0.024 and 0.010).

Conclusions

The AVG and the S/T ratio by reconstructed 3D-CT are important preoperative radiologic predictors for pathologic risk grading. The two cutoff values of AVG and S/T ratio are recommended in decision-making for patients with clinical stage IA lung adenocarcinoma with ground glass components.

Modified Histologic Classification as a Prognostic Factor in Pulmonary Adenocarcinoma

Background. The histologic pattern of pulmonary adenocarcinoma is highly heterogeneous and considered to be an important prognostic factor. The predominant histologic pattern is emphasized in the 2011 International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society classification, but few studies present a detailed investigation of the histologic changes and prognosis pulmonary adenocarcinoma using resected specimens. Methods. We examined 125 cases of surgically resected pulmonary adenocarcinoma and carefully observed histologic patterns. Invasive adenocarcinoma was divided into 3 groups according to a modified histologic classification system: group 1 had a lepidic or papillary predominant pattern with ≤10% solid or micropapillary pattern; group 2 had an acinar predominant pattern with ≤10% of the solid or micropapillary pattern; and group 3 had a solid or micropapillary predominant pattern, or any predominant pattern with >10% solid or micropapillary pattern. Results. Proportions of predominant lepidic, papillary, acinar, solid, and micropapillary patterns were 11 (9.3%), 8 (6.8%), 54 (45.8%), 38 (32.2%), and 7 (5.9%), respectively. Vague areas between 2 different patterns were frequently observed, which were considered as transitional areas for one pattern to the other pattern (gradual dedifferentiation). Modified histologic classification was significantly associated with disease-free and overall survival rate ( P = .026 and .010, respectively) using the Kaplan–Meier survival test, and an independent prognostic factor ( P = .016) in overall survival using the Cox regression test. Conclusion. Pulmonary adenocarcinoma demonstrates heterogeneous histologic patterns with gradual dedifferentiation, and this modified histologic classification is an important prognostic factor for patients with pulmonary adenocarcinoma.

The novel histologic International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification system of lung adenocarcinoma is a stage-independent predictor of survival

PURPOSE

Our aim was to analyze and validate the prognostic impact of the novel International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) proposal for an architectural classification of invasive pulmonary adenocarcinomas (ADCs) across all tumor stages.

PATIENTS AND METHODS

The architectural pattern of a large cohort of 500 patients with resected ADCs (stages I to IV) was retrospectively analyzed in 5% increments and classified according to their predominant architecture (lepidic, acinar, solid, papillary, or micropapillary), as proposed by the IASLC/ATS/ERS. Subsequently, histomorphologic data were correlated with clinical data, adjuvant therapy, and patient outcome.

RESULTS

Overall survival differed significantly between lepidic (78.5 months), acinar (67.3 months), solid (58.1 months), papillary (48.9 months), and micropapillary (44.9 months) predominant ADCs (P = .007). When patterns were lumped into groups, this resulted in even more pronounced differences in survival (pattern group 1, 78.5 months; group 2, 67.3 months; group 3, 57.2 months; P = .001). Comparable differences were observed for overall, disease-specific, and disease-free survival. Pattern and pattern groups were stage- and therapy-independent prognosticators for all three survival parameters. Survival differences according to patterns were influenced by adjuvant chemoradiotherapy; in particular, solid-predominant tumors had an improved prognosis with adjuvant radiotherapy. The predominant pattern was tightly linked to the risk of developing nodal metastases (P < .001).

CONCLUSION

Besides all recent molecular progress, architectural grading of pulmonary ADCs according to the novel IASLC/ATS/ERS scheme is a rapid, straightforward, and efficient discriminator for patient prognosis and may support patient stratification for adjuvant chemoradiotherapy. It should be part of an integrated clinical, morphologic, and molecular subtyping to further improve ADC treatment.

International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma

INTRODUCTION

Adenocarcinoma is the most common histologic type of lung cancer. To address advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma, an international multidisciplinary classification was sponsored by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. This new adenocarcinoma classification is needed to provide uniform terminology and diagnostic criteria, especially for bronchioloalveolar carcinoma (BAC), the overall approach to small nonresection cancer specimens, and for multidisciplinary strategic management of tissue for molecular and immunohistochemical studies.

METHODS

An international core panel of experts representing all three societies was formed with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. A systematic review was performed under the guidance of the American Thoracic Society Documents Development and Implementation Committee. The search strategy identified 11,368 citations of which 312 articles met specified eligibility criteria and were retrieved for full text review. A series of meetings were held to discuss the development of the new classification, to develop the recommendations, and to write the current document. Recommendations for key questions were graded by strength and quality of the evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation approach.

RESULTS

The classification addresses both resection specimens, and small biopsies and cytology. The terms BAC and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced such as adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with ≤ 5 mm invasion (MIA) to define patients who, if they undergo complete resection, will have 100% or near 100% disease-specific survival, respectively. AIS and MIA are usually nonmucinous but rarely may be mucinous. Invasive adenocarcinomas are classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous BAC), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous BAC), colloid, fetal, and enteric adenocarcinoma. This classification provides guidance for small biopsies and cytology specimens, as approximately 70% of lung cancers are diagnosed in such samples. Non-small cell lung carcinomas (NSCLCs), in patients with advanced-stage disease, are to be classified into more specific types such as adenocarcinoma or squamous cell carcinoma, whenever possible for several reasons: (1) adenocarcinoma or NSCLC not otherwise specified should be tested for epidermal growth factor receptor (EGFR) mutations as the presence of these mutations is predictive of responsiveness to EGFR tyrosine kinase inhibitors, (2) adenocarcinoma histology is a strong predictor for improved outcome with pemetrexed therapy compared with squamous cell carcinoma, and (3) potential life-threatening hemorrhage may occur in patients with squamous cell carcinoma who receive bevacizumab. If the tumor cannot be classified based on light microscopy alone, special studies such as immunohistochemistry and/or mucin stains should be applied to classify the tumor further. Use of the term NSCLC not otherwise specified should be minimized.

CONCLUSIONS

This new classification strategy is based on a multidisciplinary approach to diagnosis of lung adenocarcinoma that incorporates clinical, molecular, radiologic, and surgical issues, but it is primarily based on histology. This classification is intended to support clinical practice, and research investigation and clinical trials. As EGFR mutation is a validated predictive marker for response and progression-free survival with EGFR tyrosine kinase inhibitors in advanced lung adenocarcinoma, we recommend that patients with advanced adenocarcinomas be tested for EGFR mutation. This has implications for strategic management of tissue, particularly for small biopsies and cytology samples, to maximize high-quality tissue available for molecular studies. Potential impact for tumor, node, and metastasis staging include adjustment of the size T factor according to only the invasive component (1) pathologically in invasive tumors with lepidic areas or (2) radiologically by measuring the solid component of part-solid nodules.

Micropapillary lung adenocarcinoma: EGFR, K-ras, and BRAF mutational profile

Micropapillary lung adenocarcinoma (MPA) has been reported as an aggressive variant of adenocarcinoma, frequently manifesting at high stage with a poor prognosis. We analyzed the clinical and molecular profile of 15 primary MPAs for K-ras, EGFR, and BRAF mutations and performed fluorescence in situ hybridization for EGFR amplification. In our study, 11 (73%) of 15 MPAs harbored mutually exclusive mutations: 5 (33%) K-ras, 3 (20%) EGFR, and 3 (20%) BRAF. Mutations in all 3 genes occurred in patients with a smoking history and tumors with mucinous differentiation and secondary lepidic, acinar, and solid growth, suggesting that in a Western population, cytomorphologic correlation with genetic mutations is more unpredictable than in Japanese cohorts. We conclude that K-ras, EGFR, and BRAF mutations are disproportionately seen in adenocarcinomas of lung with a dominant micropapillary growth pattern compared with conventional adenocarcinoma in our institutional experience.

Lung adenocarcinoma: modification of the 2004 WHO mixed subtype to include the major histologic subtype suggests correlations between papillary and micropapillary adenocarcinoma subtypes, EGFR mutations and gene expression analysis

The histologic heterogeneity of lung adenocarcinoma creates a variety of complex challenges to pathologists in analyzing the various subtypes. Current classification schemas do not take into account the major subtype. We analyzed 100 cases for clinical, pathologic, and molecular features using a modification of the 2004 World Health Organization (WHO) classification to record the major component in the mixed subtype tumors. The tumors were analyzed for KRAS mutation and epidermal growth factor receptor (EGFR) by mutation, chromogenic in situ hybridization, and immunohistochemistry for EGFR and phosphorylated EGFR. Gene expression analysis was performed using HG-U133A Affymetrix oligonucleotide microarrays revealing 3 gene clusters. The most common major histologic subtype was papillary (37%) followed by acinar (30%), solid (25%) and bronchioloalveolar (7%) carcinoma (BAC), although no pure BACs were seen. Sixteen tumors harbored EGFR mutations and 14 KRAS mutations. Papillary adenocarcinoma strongly correlated with EGFR mutation (P<0.001) and gene profile Cluster 1 (P=0.006) with weaker correlations with low grade (P=0.038) and favorable behavior in Stage 1 patients (P=0.047). Micropapillary subtype correlated strongly with EGFR mutation (P<0.001) and weakly with Cluster 1 (P=0.030). Solid adenocarcinoma strongly correlated with gene profile Cluster 3 (P=0.001) and worse survival (P=0.001). BAC as a major component strongly correlated with gene Cluster 2 (P=0.001). Cluster 1 correlated strongly with less smoking (P<0.001), papillary histology (P<0.001), and EGFR mutations (P<0.001). Cluster 3 strongly correlated with heavier smoking (P<0.001), larger tumor size (P<0.001), solid subtype (P<0.001), and poor grade (P=0.004); weak correlations were found with KRAS mutation (P=0.025). No correlation was found with BAC and EGFR by mutation, chromogenic in situ hybridization or immunohistochemistry. Higher stage (P<0.001), grade (P<0.001), and solid subtype (P=0.001) correlated with shorter survival. Our data suggest that EGFR mutations are associated with papillary adenocarcinoma and gene profile Cluster 1. We discovered this only because we used a comprehensive approach examining in detail all histologic subtypes and we modified the 2004 WHO mixed subtype to include the major histologic subtype. As we do not know the major genetic pathways of 30% to 70% of lung adenocarcinomas, the comprehensive histologic subtyping we propose gives advantage for recognition of unanticipated histologic-genetic correlations that might not be detected using classification systems that focus primarily on specific aspects of adenocarcinomas such as BAC or EGFR mutations. Such an approach should be considered in future studies for validation in other datasets.

Analysis of expression patterns of breast cancer-specific markers (mammaglobin and gross cystic disease fluid protein 15) in lung and pleural tumors

CONTEXT

The lung is the most common site of metastasis during the natural history of malignant tumors. Breast carcinoma has a propensity for distant metastasis, and the lung and pleura are among the most common metastatic sites. Although it is often difficult to make a clear-cut differential diagnosis between the two, distinguishing primary lung carcinoma from breast carcinoma metastatic to the lung is important because the treatment modalities are different.

OBJECTIVE

To elucidate the utility of mammaglobin and gross cystic disease fluid protein 15 (GCDFP-15), which are known to be breast-specific antigens, in distinguishing various primary lung and pleural tumors from breast carcinoma metastasizing to the lung.

DESIGN

A total of 20 cases of breast carcinoma metastatic to the lung and 263 tumors of nonbreast origin located in the lung and pleura were analyzed.

RESULTS

Of the 20 cases of breast carcinoma metastatic to the lung, 10 (50.0%) were immunoreactive for mammaglobin and 9 (45.0%) for GCDFP-15, the frequency of positivity being slightly higher for the former than for the latter. The area immunopositive for mammaglobin showed more diffuse staining than the area immunopositive for GCDFP-15. Furthermore, the specificity of mammaglobin for breast carcinoma metastatic to the lung was superior (98.9%) to that of GCDFP-15 (91.8%).

CONCLUSION

The sensitivity of mammaglobin is equal or superior to that of GCDFP-15 for investigation of breast carcinoma. Immunopositivity for mammaglobin is more diffuse than that for GCDFP-15. In terms of practical diagnosis, mammaglobin immunohistochemistry can serve as a differential marker of breast carcinoma and should be added to the immunohistochemical panel.

Gene expression profiling reveals reproducible human lung adenocarcinoma subtypes in multiple independent patient cohorts

PURPOSE

Published reports suggest that DNA microarrays identify clinically meaningful subtypes of lung adenocarcinomas not recognizable by other routine tests. This report is an investigation of the reproducibility of the reported tumor subtypes.

METHODS

Three independent cohorts of patients with lung cancer were evaluated using a variety of DNA microarray assays. Using the integrative correlations method, a subset of genes was selected, the reliability of which was acceptable across the different DNA microarray platforms. Tumor subtypes were selected using consensus clustering and genes distinguishing subtypes were identified using the weighted difference statistic. Gene lists were compared across cohorts using centroids and gene set enrichment analysis.

RESULTS

Cohorts of 31, 72, and 128 adenocarcinomas were generated for a total of 231 microarrays, each with 2,553 reliable genes. Three adenocarcinoma subtypes were identified in each cohort. These were named bronchioid, squamoid, and magnoid according to their respective correlations with gene expression patterns from histologically defined bronchioalveolar carcinoma, squamous cell carcinoma, and large-cell carcinoma. Tumor subtypes were distinguishable by many hundreds of genes, and lists generated in one cohort were predictive of tumor subtypes in the two other cohorts. Tumor subtypes correlated with clinically relevant covariates, including stage-specific survival and metastatic pattern. Most notably, bronchioid tumors were correlated with improved survival in early-stage disease, whereas squamoid tumors were associated with better survival in advanced disease.

CONCLUSION

DNA microarray analysis of lung adenocarcinomas identified reproducible tumor subtypes which differ significantly in clinically important behaviors such as stage-specific survival.

Bronchioloalveolar carcinoma: a review

Bronchioloalveolar carcinoma (BAC) is classified as a subset of lung adenocarcinoma but has a distinct clinical presentation, tumor biology, response to therapy, and prognosis compared with other subtypes of non-small-cell lung carcinoma (NSCLC). Bronchioloalveolar carcinoma disproportionately affects women, never-smokers, and Asians and is characterized by growth along alveolar septae without evidence of stromal, vascular, or pleural invasion. Although pure BAC accounts for approximately 4% of lung cancers, tumors with histologically mixed BAC and adenocarcinoma account for > 20% of all NSCLCs, and the incidence of BAC might be increasing. Bronchioloalveolar carcinoma histology is most commonly found in small lesions identified incidentally on chest radiographs or computed tomography scans and might represent a precursor lesion to invasive adenocarcinoma. As with other subsets of NSCLC, surgical resection is the only potentially curative treatment. Patients with unresectable BAC are more likely to respond to the epidermal growth factor receptor tyrosine kinase inhibitors gefitinib and erlotinib than patients with other subtypes of NSCLC. Stage for stage, patients with BAC have a higher rate of long-term survival but might have an increased rate of intrathoracic recurrence than patients with other subtypes of NSCLC.

Comparison of the immunophenotypes of signet-ring cell carcinoma, solid adenocarcinoma with mucin production, and mucinous bronchioloalveolar carcinoma of the lung characterized by the presence of cytoplasmic mucin

The latest World Health Organization (WHO) classification divides adenocarcinoma mainly into adenocarcinoma mixed subtypes, acinar adenocarcinoma, papillary adenocarcinoma, bronchioloalveolar carcinoma, and solid adenocarcinoma with mucin production, and it mentions several variants, including fetal adenocarcinoma, mucinous ("colloid") adenocarcinoma, mucinous cystadenocarcinoma, signet-ring adenocarcinoma, and clear cell adenocarcinoma. In general, the mucin-producing adenocarcinoma of the lung comprises signet-ring cell carcinoma (SRCC), solid adenocarcinoma with mucin production (SA), and mucinous bronchioloalveolar carcinoma (m-BAC), mucinous ("colloid") adenocarcinomas and/or mucinous cystadenocarcinoma, and mucoepidermoid carcinoma. As SRCC, SA, and m-BAC exhibit distinct clinical features, it is important to identify differences in their immunohistochemical characteristics to better understand their histogenesis. In this study we analysed SRCC, SA, m-BAC, normal lung, and foregut-related secretory tissue for immunohistochemical differences using tissue microarrays. SRCC and SA showed high expression of MUC1 (97.4% and 100%, respectively), cytokeratin (CK) 7 (both 100%), and thyroid transcription factor-1 (TTF-1) (81.1% and 100%, respectively). They also showed low expression of MUC5AC (25.5% and 21.1%, respectively) and MUC6 (18.3% and 10.5%, respectively), whereas m-BAC showed high expression of MUC5AC (97.5%), MUC6 (75.0%), and CK7 (94.7%), but low expression of MUC1 (57.5%), and TTF-1 (27.5%). Hierarchical clustering showed that the immunophenotypes of SRCC and SA belong to the same category as alveolar lining cells, whereas m-BAC clustered onto another branch with gastric foveolar cells and bronchial goblet cells. These immunohistochemical findings support the results of our previous clinicopathological analysis of SRCC of the lung showing that SRCC occurs anatomically in the peripheral portion of the lung rather than in the bronchial gland-bearing portion.

Papillary adenocarcinoma of the lung is a more advanced adenocarcinoma than bronchioloalveolar carcinoma that is composed of two distinct histological subtypes

To clarify the clinicopathological nature of papillary adenocarcinoma (PA) of the lung, 20 cases of PA were collected consecutively from resected adenocarcinoma of the lung, studied immunohistochemically and, using molecular techniques, compared with bronchioloalveolar carcinoma (BAC). Clinicopathologically, PA occurred in 7.4% and dominantly in female patients. Morphologically, PA was divided into two subtypes according to the presence of residual alveolar structures, detected by elastica van Gieson stain. One of these subtypes was closely related to the morphology of BAC and might be diagnosed as adenocarcinoma with mixed subtypes. The other PA subtype was composed of tall columnar cells and grew compressively, which was similar to type F adenocarcinoma previously reported by Noguchi et al. Immunohistochemical studies using lung tissue-specific antigens, progression markers and tumor suppressor products found that PA seemed a more advanced adenocarcinoma than BAC, but no differences were observed among PA subtypes. Molecular biological analysis using three microsatellite markers at chromosome 3p revealed more frequent loss of heterozygosity in PA than BAC, with no differences among PA subtypes. These findings suggest that PA is a more advanced adenocarcinoma subtype than BAC. Further investigations are needed to clarify true PA as clinicopathologically and biologically independent from other histological subtypes of adenocarcinoma of the lung.