Is the size of the lepidic component negligible when measuring the size of the tumor to determine the stage of lung adenocarcinoma?

Background

After applying the 8th edition of the TNM staging system, the invasive component size, not total tumor size, began to be used as a T descriptor for the stage. The aim of this study was to evaluate whether the size of the lepidic component can be negligible when using only the invasive component size as the T descriptor.

Methods

From 2010 to 2018, 613 consecutive patients were diagnosed as having stage IA lung adenocarcinoma and underwent anatomical lobectomy at a tertiary hospital. Pathologic specimens and medical records were reviewed retrospectively. Statistical analyses were conducted to find out whether the recurrence of stage IA lung adenocarcinoma was more affected by total tumor size (including lepidic component size) or invasive component size.

Results

The 5-year recurrence-free survival (RFS) rates of stage 0, stage IA1, stage IA2, and stage IA3 were 100%, 98.4%, 89.1%, and 81.7%, respectively. In multivariate analysis, total tumor size was not a risk factor for recurrence, whereas invasive component size was a significant risk factor for recurrence (Hazard ratio =1.658, P=0.043). In subgroup analysis, 5-year RFS rates of large lung adenocarcinoma (total tumor size >3 cm) and others (total tumor size ≤3 cm) in the same invasive component size group (stage IA2 and stage IA3) were not statistically different.

Conclusions

Invasive component size was a risk factor for recurrence of stage IA lung adenocarcinoma, while total tumor size was not a risk factor. Therefore, it seems to be appropriate to ignore the size of the lepidic component.

Pseudocarcinomatous Mesothelioma: A Hitherto Unreported Presentation closely simulating primary lung cancer

Malignant mesothelioma (MM) has a wide range of clinical, radiologic, and pathologic presentations, mimicking lung cancer or interstitial lung diseases when predominantly involving the lung parenchyma. The case herein refers to a 79-year-old man, active smoker without asbestos exposure, incidentally discovered to have a pulmonary nodule in the right upper lobe (1.5 cm). The lesion was misinterpreted as primary lung adenocarcinoma at the frozen section in light of the predominant lepidic growth pattern. Definitive examination confirmed neoplastic proliferation along alveolar structures. However, the unusual globous shape of tumor cells along the alveoli abruptly merging with normal pneumocytes prompted us to perform some immunostains that surprisingly revealed a mesothelial differentiation (positive staining with calretinin, cytokeratins (CK5/6), D2-40, and negativity with BRCA-associated protein 1 (BAP1), Thyroid Transcription Factor 1 [TTF-1], claudin-4, carcinoembryonic antigen [CEA], and napsin). MM represents the pathologic counterpart of so-called pseudomesotheliomatous carcinoma, since it appears as a localized pulmonary neoplastic nodule displaying a predominant lepidic growth pattern (pseudocarcinomatous mesothelioma). The challenging diagnostic features of this unique case and a review of similar cases in the literature are discussed.

Differences of tumor microenvironment between stage I lepidic-positive and lepidic-negative lung adenocarcinomas

OBJECTIVE

Lepidic growth is a noninvasive component of lung adenocarcinoma. Many adenocarcinoma cases contain coexistent lepidic and nonlepidic (invasive) components (lepidic-growth positive [Lep+] adenocarcinoma); however, some cases comprise only nonlepidic components (lepidic-growth negative [Lep-] adenocarcinoma). The aim of this study was to investigate the biological differences between the invasive components of Lep+ and Lep- adenocarcinoma.

METHODS

We investigated the clinicopathologic characteristics of 232 adenocarcinomas (116 size-matched tumor pairs from Lep+ and Lep- adenocarcinomas). We then evaluated the cancer cell-specific expression levels of cancer stem cell, hypoxia, and invasion molecules in these lesions. The number of tumor-promoting stromal cells, including podoplanin-positive cancer-associated fibroblasts and CD204-positive tumor-associated macrophages, was also analyzed.

RESULTS

Among cases with size-matched invasive components, significant differences were shown in total tumor size and predominant subtype in invasive component between Lep+ and Lep- adenocarcinomas. The expression levels of hypoxia-related molecules were significantly lower in Lep+ adenocarcinomas (glucose transporter 1: 0 vs 10, P < .01; carbonic anhydrase IX: 0 vs 0 [mean, 4.7 vs 14.1], P = .01). The number of podoplanin-positive cancer-associated fibroblasts and CD204-positive tumor-associated macrophages was significantly lower in Lep+ adenocarcinomas (podoplanin-positive cancer-associated fibroblasts: 0 vs 0 [mean: 1.6 vs 11.6], P < .01; CD204-positive tumor-associated macrophages: 8.7 vs 24.7, P < .01).

CONCLUSIONS

Our results indicated that lower cancer cell-specific expression levels of hypoxia markers and a smaller number of tumor-promoting stromal cells in invasive component were characteristic features of Lep+ adenocarcinomas.

Survival and risk factors for progression after resection of the dominant tumor in multifocal, lepidic-type pulmonary adenocarcinoma

BACKGROUND

It remains unclear whether a dominant lung adenocarcinoma that presents with multifocal ground glass opacities (GGOs) should be treated by local therapy. We sought to address survival in this setting and to identify risk factors for progression of unresected GGOs.

METHODS

Retrospective review of 70 patients who underwent resection of a pN0, lepidic adenocarcinoma, who harbored at least 1 additional GGO. Features associated with GGO progression were determined using logistic regression and survival was evaluated using the Kaplan-Meier method.

RESULTS

Subjects harbored 1 to 7 GGOs beyond their dominant tumor (DT). Mean follow-up was 4.1 ± 2.8 years. At least 1 GGO progressed after DT resection in 21 patients (30%). In 11 patients (15.7%), this progression prompted resection (n = 5) or stereotactic radiotherapy (n = 6) at mean 2.8 ± 2.3 years. Several measures of the overall tumor burden were associated with GGO progression (all P values < .03) and with progression prompting intervention (all P values < .01). In logistic regression, greater DT size (odds ratio, 1.07; 95% confidence interval, 1.01-1.14) and an initial GGO > 1 cm (odds ratio, 4.98; 95% confidence interval, 1.15-21.28) were the only factors independently associated with GGO progression. Survival was not negatively influenced by GGO progression (100% with vs 80.7% without; P = .1) or by progression-prompting intervention (P = .4).

CONCLUSIONS

At 4.1-year mean follow-up, 15.7% of patients with unresected GGOs after resection of a pN0 DT underwent subsequent intervention for a progressing GGO. Some features correlated with GGO growth, but neither growth, nor need for an intervention, negatively influenced survival. Thus, even those at highest risk for GGO progression should not be denied resection of a DT.

Surgical pathology of early stage non-small cell lung carcinoma

The histologic classification of non-small cell lung carcinoma (NSCLC), particularly adenocarcinoma (ADC), has undergone extensive study in recent decades, ultimately resulting in an extensively updated classification system. The 2015 World Health Organization (WHO) classification of ADC provides greatly improved prognostic information in comparison to the 2004 WHO classification. Several issues still require further investigation: lepidic predominant ADC, prognostic significance of poor prognostic subtypes such as micropapillary carcinoma, the more recently described concept of spread of tumor through airspaces (STAS), and the utility of sublobar resections. While limited resection appears to be suitable for tumors with a ground glass radiographic appearance, which typically correspond to adenocarcinoma in situ (MIS) or minimally invasive adenocarcinoma (MIA) histologically, the role of sublobar resection in radiographic solid tumors is not as clear, and the impact of histologic subtypes with a poor prognosis needs further evaluation. Squamous cell carcinoma (SCC) has not been as extensively studied and the current classification lacks subclassification with significant prognostic information.

Morphometry analysis of lymphatics in pulmonary adenocarcinomas with a lepidic growth pattern

Lymph vessels play an important role in tumor progression. Pulmonary adenocarcinomas, accounting for half of non-small-cell lung carcinomas, compose a spectrum of histological types, exclusively or without a lepidic growth pattern (LGP) along preserved interalveolar septa. In that context, this study was designed to investigate the lymphatic vascular pattern associated with LGP and the concomitant invasive component of pulmonary adenocarcinomas. Using the D2-40 monoclonal antibody as a marker of lymphatic endothelial cells, the lymphatic vessel density (LVD) and vessel-area fraction (LVAF) were morphometrically analyzed in four adenocarcinomas in situ (AIS) and the LGP of eight invasive adenocarcinomas (LPIA), and compared with their invasive pattern (IPIA). LVD in AIS (2.1 ± 0.7 mm(-2)) and LPIA (2.4 ± 1 mm(-2)) were significantly lower than that in IPIA (14.9 ± 13.6 mm(-2)) (p=0.001). Moreover, the lymphatic vascular pattern in LGP was similar to that of normal lung, with isolated small lymphatic vessels within the interalveolar septa. Our results showing the scarcity of lymphatics in LGP suggest an absence of septal lymphangiogenesis associated with the LGP pattern in lung adenocarcinomas, which could explain, at least partially, the better prognosis observed in tumors with exclusive or predominant lepidic spread compared with other subtypes.

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.