Atypical adenomatous hyperplasia of the lung in autopsy cases

Impact of risk factors on early cancer evolution

Recent identification of oncogenic cells within healthy tissues and the prevalence of indolent cancers found incidentally at autopsies reveal a greater complexity in tumor initiation than previously appreciated. The human body contains roughly 40 trillion cells of 200 different types that are organized within a complex three-dimensional matrix, necessitating exquisite mechanisms to restrain aberrant outgrowth of malignant cells that have the capacity to kill the host. Understanding how this defense is overcome to trigger tumorigenesis and why cancer is so extraordinarily rare at the cellular level is vital to future prevention therapies. In this review, we discuss how early initiated cells are protected from further tumorigenesis and the non-mutagenic pathways by which cancer risk factors promote tumor growth. By nature, the absence of permanent genomic alterations potentially renders these tumor-promoting mechanisms clinically targetable. Finally, we consider existing strategies for early cancer interception with perspectives on the next steps for molecular cancer prevention.

Lung cancer: Premalignant biology and medical prevention

Lung cancer (both adenocarcinoma and squamous cell) progress through a series of pre-malignant histologic changes before the development of invasive disease. Each of these carcinogenic cascades is defined by genetic and epigenetic alterations in pulmonary epithelial cells. Additionally, alterations in the immune response, progenitor cell function, mutational burden, and microenvironmental mediated survival of mutated clones contribute to the risk of pre-malignant lesions progressing to cancer. Medical preventions studies have been completed and current and future trials are informed by the improved understanding of pre-malignancy. This will lead to precision chemoprevention trials based on lesional biology and histologic characteristics.

Association of CYP19A1 polymorphisms with risks for atypical adenomatous hyperplasia and bronchioloalveolar carcinoma in the lungs

Estrogen has been indicated to play an etiological role in the development of lung adenocarcinoma (ADC), particularly bronchioloalveolar carcinoma (BAC), a type of ADC that develops from a benign adenomatous lesion, atypical adenomatous hyperplasia (AAH). Polymorphisms in the CYP19A1 gene cause interindividual differences in estrogen levels. Here, 13 CYP19A1 single-nucleotide polymorphisms (SNPs) were examined for associations with lung AAH risk. AAH is detected as ground-glass opacity (GGO) by computed tomography (CT) examination, and this study consisted of 100 individuals diagnosed with GGO in their lungs among 3088 CT-based cancer screening examinees and 424 without. Minor allele carriers for the rs3764221 SNP showed an elevated risk for GGO [odds ratio (OR) = 1.72, P = 0.017]. Associations of this SNP with risks for lung AAH and BAC in the lungs were next examined using 359 ADC cases whose resected lung lobes were subjected to a histological examination for AAH accompaniment and the presence of BAC components and 330 controls without cancer. The ORs were also increased for lung ADC accompanied by AAH (OR = 1.74, P = 0.029) as well as lung ADC with BAC components (OR = 1.41, P = 0.091). The minor allele was associated with an increased circulating estradiol level (P = 0.079) in a population of 363 postmenopausal women without cancer. These results indicate that CYP19A1 polymorphisms are involved in the risk for lung AAH and BAC in the lungs by causing differences in estrogen levels.

Clinicopathologic analysis of multiple (five or more) atypical adenomatous hyperplasias (AAHs) of the lung: evidence for the AAH-adenocarcinoma sequence

OBJECTIVE

Clarification of the clinicopathologic characteristics of patients with multiple atypical adenomatous hyperplasias (AAHs).

MATERIALS AND METHODS

The subjects were 1,639 patients who underwent lobectomy or pneumonectomy for lung tumors. The clinicopathologic features of the AAHs in the lung background and the main tumors were examined with regard to the number and the size of the AAHs, the incidence and histology of adenocarcinomas (ADs), and the outcome.

RESULTS

Thirty-two patients (2.0%) had 5 or more AAHs (ranging from 5 to 171), being present predominantly in the upper lobe (86%) and in women (75%). Among the 794 AAHs, 495 (62%) measured less than 1 mm, 170 (22%) measured 1 to less than 2 mm, 118 (15%) measured 2 to less than 5 mm, and 11 (1%) measured 5 to less than 10 mm. Twenty-eight patients (88%) had AD (1 in 18 patients and 2 to 6 in 10 patients). Thirty-two of the 51 patients with ADs (63%) had an AAH component. The incidence of ADs among the total of both AAHs and ADs was 6.0% (51 of 845). The 5-year cancer-free survival rate was 71.4%.

CONCLUSION

Five or more AAHs were seen in the background in 2.0% of lung tumors. Most of the AAHs were small, measuring less than 2 mm, and few exceeded 5 mm. Most of the patients had ADs, which were histologically suggested to be derived from AAH. However, the incidence of the AAH-AD sequence was considered to be low at the tumor basis, and the outcome of ADs was not very favorable.

The Classification of Lung Carcinoma: Time to Change the Morphology-Based Approach?

Morphology still remains the cornerstone in lung cancer classification and always has been accompanying pathologists in their daily activity, even though several ancillary techniques have been incorporated over time to improve diagnostic, prognostic, and predictive capabilities in lung cancer. Currently, we are also faced with a global rethinking of lung cancer care, especially once novel therapy strategies have been made available on the basis of the diverse characteristics of tumors. Although morphology still remains a not easily replaceable tool for lung cancer classification, we are now challenged by the need of offering clinicians more detailed subtyping of non-small-cell lung cancer especially in event of limited diagnostic material, poorly differentiated tumors, or unresectable lesions. Close integration of improved morphology, immunohistochemistry, and molecular tests will be able to not only sharpen our diagnostic algorithms and prognostic and predictive potentialities but also get insights into several lung cancer biology issues, such as histogenesis and new classification schemes.

High-resolution computed tomography screening for lung cancer: unexpected findings and new controversies regarding adenocarcinogenesis

CONTEXT

Recent advances in human imaging technologies reawakened interest in lung cancer screening. Although historic and current preliminary and noncontrolled studies have not shown a decrease in lung cancer mortality in screened populations, many explanations have been proffered while the lung cancer community awaits the results of several large controlled population studies.

OBJECTIVE

To critically review the current model of adenocarcinoma development against the background of lung cancer screening results combined with observational pathologic and radiographic studies.

DATA SOURCES

Published articles pertaining to lung cancer screening, lung adenocarcinoma pathology, and radiology accessible through PubMed form the basis for this review.

CONCLUSIONS

The current adenocarcinogenesis model is probably valid for many but not all lung adenocarcinomas. Screening data combined with radiographic and pathologic studies suggest that not all lung adenocarcinomas are clinically aggressive, and it is uncertain whether all aggressive adenocarcinomas arise from identified precursors.

Molecular Basis of Pulmonary Disease

Pulmonary pathology includes a large spectrum of both neoplastic and non-neoplastic diseases that affect the lung. Many of these are a result of the unusual relationship of the lung with the outside world. Every breath that a human takes brings the outside world into the body in the form of infectious agents, organic and inorganic particles, and noxious agents of all types. Although the lung has many defense mechanisms to protect itself from these insults, these are not infallible; therefore, lung pathology arises. Damage to the lung is particularly important given the role of the lung in the survival of the organism. Any impairment of lung function has widespread effects throughout the body, since all organs depend on the lungs for the oxygen they need. Pulmonary pathology catalogs the changes in the lung tissues and the mechanisms through which these occur. This chapter presents a review of lung pathology and the current state of knowledge about the pathogenesis of each disease. It suggests that a clear understanding of both morphology and mechanism is required for the development of new therapies and preventive measures.

Association of KRAS polymorphisms with risk for lung adenocarcinoma accompanied by atypical adenomatous hyperplasias

The pulmonary adenoma susceptibility 1 (Pas1) gene affects susceptibility to the development of lung adenomas in mice with a subset of the adenomas progressing to adenocarcinoma (ADC). In this study, genotype distributions for 10 polymorphisms in the human counterparts for three mouse candidate Pas1 genes, KRAS, CASC1/LAS1 and LRMP, were examined in a hospital-based case-control study consisting of 364 lung ADC cases and 253 controls. All the ADC cases were subjected to lobectomy and subsequent pathological investigation of atypical adenomatous hyperplasia (AAH), a putative precursor for peripheral lung ADC, including bronchioloalveolar carcinoma, in the resected lobes. Eighty-one (22%) of the ADC cases carried at least one AAH lesion in addition to the primary ADC and 34 (9%) of them carried multiple AAH lesions. None of the 10 polymorphisms examined showed significant associations with overall lung ADC risk (P > 0.05). However, minor allele carriers for two polymorphisms in the KRAS gene, KRAS-1 and -6, showed significantly increased odds ratios (ORs) for ADC accompanied by multiple AAHs [OR = 3.0; 95% confidence interval (CI) = 1.4-6.2, P = 0.004 and OR = 2.4; 95% CI = 1.1-4.7, P = 0.02, respectively]. Minor haplotypes including the minor allele for the KRAS-6 polymorphism showed increased ORs for ADC accompanied by multiple AAHs, and KRAS transcripts from the minor allele for this polymorphism were more abundantly detected in lung tissues than those from the major allele. Thus, KRAS polymorphisms were indicated to be involved in risk for the development of AAHs that progress to ADC by causing differential KRAS oncogene expression in the lungs.

Lung cancer preneoplasia

From histological and biological perspectives, lung cancer is a complex neoplasm. Although the sequential preneoplastic changes have been defined for centrally arising squamous carcinomas of the lung, they have been poorly documented for the other major forms of lung cancers, including small cell lung carcinoma and adenocarcinomas. There are three main morphologic forms of preneoplastic lesions recognized in the lung: squamous dysplasias, atypical adenomatous hyperplasia, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. However, these lesions account for the development of only a subset of lung cancers. Several studies have provided information regarding the molecular characterization of lung preneoplastic changes, especially for squamous cell carcinoma. These molecular changes have been detected in the histologically normal and abnormal respiratory epithelium of smokers. Two different molecular pathways have been detected in lung adenocarcinoma pathogenesis: smoking-associated activation of RAS signaling, and nonsmoking-associated activation of EGFR signaling; the latter is detected in histologically normal respiratory epithelium.

CT detected indeterminate pulmonary nodules in a chemoprevention trial of fluticasone

INTRODUCTION

In animal models of lung carcinogenesis, inhaled corticosteroids appear to reduce the number of new lung tumors. In a trial of budesonide in smokers with bronchial dysplasia, the proportion of indeterminate CT detected pulmonary nodules that resolved was larger in the treatment group. We performed a secondary analysis of CT data of subjects at risk of lung cancer enrolled in a chemoprevention trial of fluticasone.

METHODS

Subjects with bronchial squamous metaplasia or dysplasia had a baseline chest CT scan. They were randomized to fluticasone or a placebo. After 6 months a repeat CT was performed and the change in number and size of nodules was evaluated.

RESULTS

Two hundred and one subjects were screened. Of the 108 volunteers included in the study, 74 were male, mean age was 53 years and mean number of pack years 48. Baseline: 35 subjects had 91 nodules in total, 62% <4mm. In the fluticasone arm more subjects had a decrease and fewer had an increase in number of nodules, however this trend did not reach statistical significance.

CONCLUSION

In this preliminary study there was a tendency of nodules to resolve, however, studies with CT detected nodules as inclusion criterion are needed.

Molecular Alterations in Atypical Adenomatous Hyperplasia Occurring in Benign and Cancer-bearing Lungs

Atypical adenomatous hyperplasia (AAH) is considered to be a precursor lesion of the lung adenocarcinoma. Several genetic abnormalities have been reported in AAH associated with adenocarcinoma, but little is known about AAH associated with benign lung lesions. To address this we compared the molecular characteristics of AAH present in benign conditions to those coexisting with carcinoma. Seven cases of AAH from resected non-neoplastic lungs (AAH-B) and 12 cases from lungs resected for primary lung carcinoma (AAH-M) were analyzed for loss of heterozygosity (LOH) using 21 polymorphic microsatellite markers situated in proximity to known tumor suppressor genes on chromosomes 3p, 5q, 7p, 9p, 10q, and 17p. Direct DNA sequencing for K-ras mutation was also performed. There was a broad range of LOH in both groups. No LOH was identified in 3 cases (25%) of AAH-M, but all cases of AAH-B showed LOH (P=0.26). Six cases (50%) of AAH-M and 3 cases (43%) of AAH-B showed loss at 1 marker (P=0.99). LOH at 2 or more markers was identified in 3 (25%) cases of AAH-M and 4 (57%) cases of AAH-B (P=0.32). LOH was most frequently detected on chromosomes 3p and 10q in both groups. The difference in overall fractional allelic loss between the 2 groups did not reach statistical significance. K-ras mutations were not identified in either group. Our results showed a significant overlap in LOH patterns between AAH with or without coexistent lung malignancy. Therefore, AAH may represent a smoking induced low-grade neoplastic lesion that may be a precursor lesion of only a subset of invasive lung adenocarcinoma.

CT findings of atypical adenomatous hyperplasia in the lung

Objective

The aim of this study was to analyze the computed tomographic (CT) findings of atypical adenomatous hyperplasia (AAH) in the lung.

Materials and Methods

The CT findings of AAHs in eight patients were retrospectively reviewed. The CT findings of each AAH lesion were evaluated for multiplicity, location, shape, size and internal density of the lesion, the interface between the normal lung and the lesion, the internal features within the lesion and any change of the lesion on the follow-up CT scans (range: 33 to 540 days; average: 145.3 days).

Results

The eight patients consisted of three men and five women (age range: 43-71 years). Six of eight patients were asymptomatic. Four of them (50%) had synchronous malignancies in the lung: adenocarcinoma of the lung (n = 3), and metastatic squamous cell carcinoma from the uterus (n = 1). We could identify and evaluate eleven AAH nodules in seven patients on the CT scans. Three patients had multiple AAHs. Seven of the 11 lesions (64%) were located in the upper lobe. All the AAHs showed a well-defined oval or round shape and pure ground-glass opacity (GGO) without any solid component (size: 3.9×3 mm to 19×17 mm; internal attenuation: -467 to -785 HU). All the AAHs showed no change of their size and internal density on the follow-up CT scans.

Conclusion

Atypical adenomatous hyperplasia is often associated with malignancy. This tumor is shown on CT as persistent well-defined oval or round nodular GGOs without solid components, and it does not change on the follow-up CT.

Atypical adenomatous hyperplasia of lung: its incidence and analysis of clinical, glycohistochemical and structural features including newly defined growth regulators and vascularization

BACKGROUND

Adenomatous hyperplasia of the peripheral lung has been suggested to be a preneoplastic lesion leading to peripherally localized lung carcinomas. The paucity of data about cellular and vascular characteristics of this lesion in comparison to normal lung prompted this investigation.

MATERIAL AND METHODS

We describe results of two investigations comprising 75 cases and 70 cases, respectively, with atypical adenomatous hyperplasia (AAH) of the lung, respectively: (a) a prospective study part with thorough analysis of surgical lung specimens (lobes and lungs) for light microscopical detection of the lesion; and (b) a retrospective study part with immuno- and lectin histochemical analysis of AAH and non-neoplastic lung parenchyma monitoring expression of growth-related markers and changes in vascularization patterns. Sections of the individual cases were examined by an image-analyzing system including automated measurement of staining intensities and structure analysis.

RESULTS

The prospective study part revealed an incidence of AAH in 2/31 cases with squamous cell carcinoma and in 5/32 cases with adenocarcinomas. No relation to pT- or pN stages was detectable, high grade AAHs were seen to be close to the tumor lesions (<2 cm distance) and those with low grade at greater distances. Statistically significantly increased levels of expression of anti-apoptotic bcl-2, macrophage migration inhibitory factor (MIF) capable to suppress p53 activities, heparin-binding lectin, interleukin-2, galectin-1 and of binding sites for the endogenous lectins galectins-1, -3 and -7 were determined. In addition, alveolar-lining cells, which express these markers, formed spatial clusters, which harbor different levels of structural entropy. AAH displayed an increased level of vascularization characterized by regular size and increased number of newly formed vessels.

INTERPRETATION

The prospective and retrospective study parts point to a close association of AAH with peripherally localized adenocarcinoma of the lung. AAH is characterized by pronounced alteration of expression of several growth-related markers and probably non-reversible changes in vascularization.