Pulmonary Adenocarcinoma In Situ: Analyses of a Large Series With Reference to Smoking, Driver Mutations, and Receptor Tyrosine Kinase Pathway Activation

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Adenocarcinoma spectrum lesions of the lung: Detection, pathology and treatment strategies

Adenocarcinoma has become the most prevalent lung cancer sub-type and its frequency is increasing. The earliest stages in the development of lung adenocarcinomas are visible using modern computed tomography (CT) as ground glass nodules. These pre-invasive nodules can progress over time to become invasive lung adenocarcinomas. Lesions in this developmental pathway are termed 'adenocarcinoma spectrum' lesions. With the introduction of lung cancer screening programs there has been an increase in the detection of these lesions raising questions about natural history, surveillance and treatment. Here we review how the radiological appearance of an adenocarcinoma spectrum lesion relates to its underlying pathology and explore the natural history and factors driving lesion progression. We examine the molecular changes that occur at each stage of adenocarcinoma spectrum lesion development, including the effects of the driver mutations, EGFR and KRAS, that are key to invasive adenocarcinoma pathology. A better understanding of the development of pre-invasive disease will create treatment targets. Our understanding of how tumours interact with the immune system has led to the development of new therapeutic strategies. We review the role of the immune system in the development of adenocarcinoma spectrum lesions. With a clear preinvasive phase there is an opportunity to treat early adenocarcinoma spectrum lesions before an invasive lung cancer develops. We review current management including surveillance, surgical resection and oncological therapy as well as exploring potential future treatment avenues.

Calretinin-expressing lung adenocarcinoma: Distinct characteristics of advanced stages, smoker-type features, and rare expression of other mesothelial markers are useful to differentiate epithelioid mesothelioma

Calretinin, a mesothelioma marker, is sometimes expressed in lung cancer, which may complicate the differential diagnosis of mesothelioma. Here, the clinicopathological and immunohistochemical characteristics of calretinin-positive lung cancer were examined to reduce confusion with malignant mesothelioma. Calretinin expression in 307 consecutive cases of lung cancer was evaluated immunohistochemically. Survival was analyzed using the Kaplan-Meier method and log-rank test. Calretinin expression was identified in 67 (22%) tumors, including those with partial and weak expression [15% (37/250) of adenocarcinomas, 54% (25/46) of squamous cell carcinomas, 75% (3/4) of adenosquamous carcinomas, and 29% (2/7) of sarcomatoid carcinomas]. In calretinin-positive adenocarcinoma (n = 37), expression percentages of Wilms tumor-1, podoplanin, thyroid transcription factor-1, and claudin-4 were 6, 3, 52, 82%, respectively, whereas in calretinin-positive squamous cell carcinoma (n = 25) the percentages were 8, 12, 12, 68%, respectively, indicating that other mesothelial markers were only rarely expressed and that claudin-4 expression was common. Although not an independent marker, calretinin expression was associated with a poor prognosis for stage I tumors of adenocarcinoma (p < 0.001) and of all histological subtypes (p < 0.001). In conclusion, calretinin-positive lung tumors share characteristics with those of smokers and advanced stages and can be differentiated from mesothelioma with the use of other mesothelial and epithelial markers.

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

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

Clinical characteristics and programmed cell death ligand-1 expression in adenocarcinoma in situ and minimally invasive adenocarcinoma of lung

Objectives

According to the IASLC/ATS/ERS 2011 classification, there are two new conceptions of lung adenocarcinoma, adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), which are very early stages of lung adenocarcinoma. This study aimed to analyze clinical features of AIS and MIA and determine the expression profile of PD-L1 in AIS and MIA.

Results

In all 274 patients, 77 were diagnosed as AIS and 197 as MIA. We accidentally found 4 patients with recurrence, which were all MIA. The median age of the patients at diagnosis was both 52 years. 71.4% were female in AIS as while as 71.1% in MIA. 36.4% patients were observed with ever symptoms in AIS and 28.9% in MIA. 12.9% and 8.6% had smoking history respectively in AIS an MIA. All AIS and MIA cases were PD-L1 negative. There was significant association between symptoms and more mild progression of nodules in chest CT before surgery.

Materials and Methods

We analyzed some clinical features of 274 patients including age, sex, smoking history, family history, surgery, EGFR mutation, ALK, ROS-1, serum CEA level et al. The expression of PD-L1 was evaluated by immunohistochemical analysis in 37 specimens of MIA and 17 specimens of AIS.

Conclusions

There are no significant differences between AIS and MIA in clinical features. AIS and MIA almost do not express PD-L1 protein and without any lymph node metastasis. The surgery intervention is supposed to be as small as possible.

The Molecular Pathology of Lung Cancer

Advances in lung cancer genomics have revolutionized the diagnosis and treatment of this heterogeneous and clinically significant group of tumors. This article provides a broad overview of the most clinically relevant oncogenic alterations in common and rare lung tumors, with an emphasis on the pathologic correlates of the major oncogenic drivers, including EGFR, KRAS, ALK, and MET. Illustrations emphasize the morphologic diversity of lung adenocarcinoma, including genotype-phenotype correlations of genomic evolution in tumorigenesis. Molecular diagnostic approaches, including PCR-based testing, massively parallel sequencing, fluorescence in situ hybridization, and immunohistochemistry are reviewed.

Size of Non-lepidic Invasive Pattern Predicts Recurrence in Pulmonary Mucinous Adenocarcinoma: Morphologic Analysis of 188 Resected Cases with Reappraisal of Invasion Criteria

Background

We reviewed a series of 188 resected pulmonary mucinous adenocarcinomas (MAs) to clarify the prognostic significance of lepidic and non-lepidic patterns.

Methods

Non-lepidic patterns were divided into bland, non-distorted acini with uncertain invasiveness (pattern 1), unequivocal invasion into stroma (pattern 2), or invasion into alveolar spaces (pattern 3).

Results

The mean proportion of invasive patterns (patterns 2 and 3) was lowest in small (≤ 3 cm) tumors, and gradually increased in intermediate (> 3 cm and ≤ 7 cm) and large (> 7 cm) tumors (8.4%, 34.3%, and 50.1%, respectively). Adjusted T (aT) stage, as determined by the size of invasive patterns, was positively correlated with adverse histologic and clinical features including older age, male sex, and ever smokers. aTis tumors, which were exclusively composed of lepidic pattern (n = 9), or a mixture of lepidic and pattern 1 (n = 40) without any invasive patterns, showed 100% disease- free survival (DFS). The aT1mi tumors, with minimal (≤ 5 mm) invasive patterns (n = 63), showed a 95.2% 5-year DFS, with recurrences (n = 2) limited to tumors greater than 3 cm in total size (n = 23). Both T and aT stage were significantly associated with DFS; however, survival within the separate T-stage subgroups was stratified according to the aT stage, most notably in the intermediatestage subgroups. In multivariate analysis, the size of invasive patterns (p = .020), pleural invasion (p < .001), and vascular invasion (p = .048) were independent predictors of recurrence, whereas total size failed to achieve statistical significance (p = .121).

Conclusions

This study provides a rationale for histologic risk stratification in pulmonary MA based on the extent of invasive growth patterns with refined criteria for invasion.