Spectrum of pulmonary neuroendocrine cell proliferation: diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, tumorlet, and carcinoids

An Illustrated Review of the Recent 2019 World Health Organization Classification of Neuroendocrine Neoplasms: A Radiologic and Pathologic Correlation

ABSTRACT

Recent advances in molecular pathology and an improved understanding of the etiology of neuroendocrine neoplasms (NENs) have given rise to an updated World Health Organization classification. Since gastroenteropancreatic NENs (GEP-NENs) are the most common forms of NENs and their incidence has been increasing constantly, they will be the focus of our attention. Here, we review the findings at the foundation of the new classification system, discuss how it impacts imaging research and radiological practice, and illustrate typical and atypical imaging and pathological findings. Gastroenteropancreatic NENs have a highly variable clinical course, which existing classification schemes based on proliferation rate were unable to fully capture. While well- and poorly differentiated NENs both express neuroendocrine markers, they are fundamentally different diseases, which may show similar proliferation rates. Genetic alterations specific to well-differentiated neuroendocrine tumors graded 1 to 3 and poorly differentiated neuroendocrine cancers of small cell and large-cell subtype have been identified. The new tumor classification places new demands and creates opportunities for radiologists to continue providing the clinically most relevant report and on researchers to design projects, which continue to be clinically applicable.

2021 WHO Classification of Lung Cancer: Molecular Biology Research and Radiologic-Pathologic Correlation

The 2021 World Health Organization (WHO) classification system for thoracic tumors (including lung cancer) contains several updates to the 2015 edition. Revisions for lung cancer include a new grading system for invasive nonmucinous adenocarcinoma that better reflects prognosis, reorganization of squamous cell carcinomas and neuroendocrine neoplasms, and description of some new entities. Moreover, remarkable advancements in our knowledge of genetic mutations and targeted therapies have led to a much greater emphasis on genetic testing than that in 2015. In 2015, guidelines recommended evaluation of only two driver mutations, ie, epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) fusions, in patients with nonsquamous non-small cell lung cancer. The 2021 guidelines recommend testing for numerous additional gene mutations for which targeted therapies are now available including ROS1, RET, NTRK1-3, KRAS, BRAF, and MET. The correlation of imaging features and genetic mutations is being studied. Testing for the immune biomarker programmed death ligand 1 is now recommended before starting first-line therapy in patients with metastatic non-small cell lung cancer. Because 70% of lung cancers are unresectable at patient presentation, diagnosis of lung cancer is usually based on small diagnostic samples (ie, biopsy specimens) rather than surgical resection specimens. The 2021 version emphasizes differences in the histopathologic interpretation of small diagnostic samples and resection specimens. Radiologists play a key role not only in evaluation of tumor and metastatic disease but also in identification of optimal biopsy targets. ©RSNA, 2024 Test Your Knowledge questions in the supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Radiological-pathological correlation in diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH): imaging and histopathology

AIM

To review histologically confirmed diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) cases and carry out a detailed pathological-radiological correlation to see if computed tomography (CT) can be used to confidently identify DIPNECH.

MATERIALS AND METHODS

Twenty-three histologically confirmed DIPNECH patients in the shared database of two NHS Trusts were reviewed. CT images were reviewed by two independent radiologists, each of them with >10 years of experience in thoracic imaging. All histological specimens were reviewed by a single pathologist with >25 years of experience. The diagnosis of DIPNECH was made according to the current World Health Organization (WHO) definition included in the WHO 2015 classification of pulmonary tumours. The results on histology were compared to the presence of nodules and air trapping on CT. Demographic information and, when available, molecular imaging studies and pulmonary function tests were also considered.

RESULTS

There are prototypal clinical and radiological findings reflecting the presence of underlying histological DIPNECH: middle-aged women with multiple small and scattered nodules due to the clustering and proliferation of neuroendocrine cells. At least one larger, dominant, lung nodule reflecting a carcinoid tumour is very common and mosaic attenuation/air trapping is seen approximately in 50% of cases in inspiratory scans. Airflow obstruction is rarely associated with histological bronchial or peribronchial fibrosis, which suggests other mechanisms must be involved in its development.

CONCLUSION

CT can be used to predict pathological DIPNECH in the appropriate clinical setting. It is important to consider DIPNECH to avoid overdiagnosis of more sinister conditions such as lung cancer or metastases.

Effective lung cancer control: An unaccomplished challenge in cancer research

Lung cancer has always been a burden to the society since its non-effective early detection and poor survival status. Different imaging modalities such as computed tomography scan have been practiced for lung cancer detection. This review focuses on the importance of sputum cytology for early lung cancer detection and biomarkers effective in sputum samples. Published articles were discussed in light of the potential of sputum cytology for lung cancer early detection and risk assessment across high-risk groups. Recent developments in sample processing techniques have documented a clear potential to improve or refine diagnosis beyond that achieved with conventional sputum cytology examination. The diagnostic potential of sputum cytology may be exploited better through the standardization and automation of sputum preparation and analysis for application in routine laboratory practices and clinical trials. The challenging aspects in sputum cytology as well as sputum-based molecular markers are to ensure appropriate standardization and validation of the processing techniques.

Quantitative Airway Assessment of Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH) on CT as a Novel Biomarker

Objectives: Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) occurs due to abnormal proliferation of pulmonary neuroendocrine cells. We hypothesized that performing a quantitative analysis of airway features on chest CT may reveal differences to matched controls, which could ultimately help provide an imaging biomarker. Methods: A retrospective quantitative analysis of chest CTs in patients with DIPNECH and age matched controls was carried out using semi-automated post-processing software. Paired segmental airway and artery diameters were measured for each bronchopulmonary segment, and the airway:artery (AA) ratio, airway wall thickness:artery ratio (AWTA ratio) and wall area percentage (WAP) calculated. Nodule number, size, shape and location was recorded. Correlation between CT measurements and pulmonary function testing was performed. Results: 16 DIPNECH and 16 control subjects were analysed (all female, mean age 61.7 +/− 11.8 years), a combined total of 425 bronchopulmonary segments. The mean AwtA ratio, AA ratio and WAP for the DIPNECH group was 0.57, 1.18 and 68.8%, respectively, compared with 0.38, 1.03 and 58.3% in controls (p < 0.001, <0.001, 0.03, respectively). DIPNECH patients had more nodules than controls (22.4 +/− 32.6 vs. 3.6 +/− 3.6, p = 0.03). AA ratio correlated with FVC (R2 = 0.47, p = 0.02). A multivariable model incorporating nodule number, AA ratio and AWTA-ratio demonstrated good performance for discriminating DIPNECH and controls (AUC 0.971; 95% CI: 0.925−1.0). Conclusions: Quantitative CT airway analysis in patients with DIPNECH demonstrates increased airway wall thickness and airway:artery ratio compared to controls. Advances in knowledge: Quantitative CT measurement of airway wall thickening offers a potential imaging biomarker for treatment response.

An Older Woman With Transient Cough, Mild Airway Obstruction, and Lung Nodules

CASE PRESENTATION

A 66-year-old woman with no significant medical history presented initially to her primary care physician's office with a 2-weeks history of productive cough and associated wheezing after cough paroxysms. Empiric antibiotic was started, with no improvement. Chest radiograph was performed, which showed bilateral nodular opacities (Fig 1). The patient's cough resolved in 6 weeks after empiric treatment with oral steroids, inhaled steroids, and bronchodilators. A follow-up chest radiograph done at 6 weeks showed persistent abnormalities, and she was referred for a pulmonary evaluation. She denied any fevers, cough, hemoptysis, shortness of breath, wheezing, loss of appetite, or weight loss at that time. She had no significant medical problems and was not on any medications at that time. She was a nonsmoker. She worked in an office setting and denied any occupational or recreational exposures or recent travels. There was no family history of lung diseases or cancer.

[Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia with tumorlet formation: A case report and review of the literature]

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia is an infrequent lesion recently classified by the WHO as preinvasive. It can present with the formation of tumorlets (neuroendocrine cell groups up to 5 mm) which result in a typical histological and radiological image. We report a case of a 67-year-old women who presented with a chronic cough. The CT scan showed bilateral minute, multiple pulmonary nodules. A biopsy revealed a diffuse idiopathic pulmonary neuroendocrine cell hyperplasia with several tumorlets. After two years of follow-up, imaging studies showed no significant changes.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia: Report of two cases

INTRODUCTION

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare disorder characterized by a proliferation of neuroendocrine cells within the lung. It is classically described as a disease with persistent cough, dyspnea and wheezing in non-smoker middle aged females. CT of the chest reveals diffuse air trapping with mosaic pattern.

PATIENTS AND METHODS

We present two cases of DIPNECH that were sent to our department to perform a lung biopsy with the diagnostic suspicion of diffuse interstitial disease. Both cases were women with a history of chronic cough and moderate effort dyspnea.

RESULTS AND DISCUSSION

The aim of this paper is that physicians take into account this diagnostic entity before treating as an asthmatic a patient with these characteristics, not forgetting that they are prenoplastic lesions.

Series of rare lung diseases mimicking imaging patterns of common diffuse parenchymal lung diseases

Diffuse parenchymal lung diseases (DPLDs) encompass a variety of restrictive and obstructive lung pathologies. In this article, the authors discuss a series of rare pulmonary entities and their high-resolution computed tomography imaging appearances, which can mimic more commonly encountered patterns of DPLDs. These cases highlight the importance of surgical lung biopsies in patients with imaging findings that do not show typical imaging features of usual interstitial pneumonia.

Imaging of Asthma

Asthma is one of the most common diseases of the lung. Asthma manifests with common, although often subjective and nonspecific, imaging features at radiography and high-resolution computed tomography. The primary role of imaging is not to make a diagnosis of asthma but to identify complications, such as allergic bronchopulmonary aspergillosis, or mimics of asthma, such as hypersensitivity pneumonitis. This article reviews the imaging features of asthma as well as common complications and mimics.

Ten Years of Chronic Cough in a 64-Year-Old Man With Multiple Pulmonary Nodules

A 64-year-old male former smoker with a history of prostate cancer presented to our pulmonary clinic, complaining of nonproductive cough for 10 years. Prior evaluation included treatment for upper airway cough syndrome and gastroesophageal reflux, stopping angiotensin-converting enzyme inhibitor, and initiation of inhaled β-agonists. Esophageal pH monitoring indicated silent reflux, and proton pump inhibitor therapy was started. He continued to cough and complain of dyspnea. Physical examination produced unremarkable results, with no evidence of lymphadenopathy. Pulmonary function tests showed a pseudo-restrictive pattern with air trapping, hyperreactivity, and incomplete bronchodilator responsiveness: FEV1, 2.48 L (69% of predicted); FVC, 3.57 L (75% of predicted); FEV1/FVC, 92%; total lung capacity, 7.00 L (100% of predicted); and residual volume, 3.05 L (136% of predicted). Laboratory studies, including a complete metabolic panel, prostate-specific antigen test, and complete blood count, yielded normal results.

Progressive dyspnea due to pulmonary carcinoid tumorlets

This is a case description of a female patient, 77 years-old, who presented with progressive dyspnea and cough. She had a mild hypoxemia in the arterial blood gases (PaO₂ 72 mmHg) and normal spirometry. The chest computer tomography revealed diffuse "ground glass" opacities, segmental alveolitis, bronchiectasis, fibrotic lesions and numerous micronodules. A thoracoscopy was performed and the obtained biopsy showed carcinoid tumorlets, with positive CK8/18, CD56, TTF-1 and synaptophysin immunohistochemical markers. Pulmonary carcinoid tumorlets are rare, benign lesions and individuals with tumorlets are typically asymptomatic. Our report presents a symptomatic clinical case of carcinoid tumorlet.

Imaging of Small Airways Diseases

Small airways disease, or bronchiolitis, encompasses many conditions that result in bronchiolar inflammation and/or fibrosis. Bronchioles are distal airways within secondary pulmonary lobules that are only visible on imaging when abnormal. High-resolution computed tomography plays an important role in diagnosing small airways disease. The predominant direct high-resolution computed tomography sign of bronchiolitis includes centrilobular nodules, whereas air trapping is the main indirect finding. This article reviews bronchiolar anatomy, discusses the differential diagnosis for cellular and constrictive bronchiolitis with a focus on key imaging features, and discusses how to distinguish important mimics.

Diffuse Neuroendocrine Cell Hyperplasia: Report of Two Cases

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare pulmonary disorder characterised by a proliferation of neuroendocrine cells within the lung. It is believed that a minority of the patients with DIPNECH can develop carcinoid tumors. Here, we report two new cases of DIPNECH with coexisting carcinoid tumors.

Pulmonary Neuroendocrine Tumors: Part I. Spectrum and Characteristics of Tumors

Pulmonary neuroendocrine tumors arise from Kulchitzky cells of the bronchial mucosa and include typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma, and small cell lung cancer. These tumors have a variable growth rate that determines their presentation and prognosis. Typical carcinoid has the lowest growth rate and better prognosis; in contrast, small cell lung cancer is an aggressive tumor with a very poor prognosis. Although there are some overlapping histologic features between these tumors, clinical, imaging, and immunohistochemical markers are useful in the differentiation of pulmonary neuroendocrine tumors. The treatment options differ on the basis of histologic characteristics. In this article, we aim to describe the spectrum of neuroendocrine tumors of the lung, except for small cell lung cancer, and their clinical, pathologic, and imaging findings, with a focus on treatment options.

Pulmonary Peripheral Carcinoids after Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia and Tumorlets: Report of 3 Cases

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) and tumorlets are neuroendocrine cells proliferations smaller than 5 mm. The former confines to bronchial/bronchiolar wall, while the latter broke through epithelial basement membrane. The authors present 3 cases of DIPNECH and tumorlets associated with a typical peripheral carcinoid tumor without underlying lung disease. The patients presented with nonspecific pulmonary symptoms: 3 females, 60, 72, and 84 years old, whose CT-scans showed well-defined pulmonary nodules, 2.2, 1.6, and 1.4 cm, respectively; first patient was submitted to lobectomy and the others underwent surgical biopsy. Whitish/brownish lobulated tumors corresponded to typical carcinoids (less than 2 mitoses/2 mm² and without necrosis); polygonal/elongated cells under lobular pattern expressed CD56, chromogranin A, synaptophysin, and CK7; Ki-67 positivity was between 1 and 3%. Bronchial/bronchiolar wall neuroendocrine cell hyperplasia and several neuroendocrine nodules under 5 mm, with identical morphologic and immunoexpression, were observed, without lung disease. Typical carcinoid associated with DIPNECH and tumorlets without other pulmonary diseases is rare. Sporadic cases may recall embryonal neuroendocrine differentiation potentiality to develop peripheral hyperplasia, most commonly in underoxygenated parenchyma. The described cases are elucidative of peripheral spectrum of neuroendocrine cell tumour evolution, reinforcing higher female incidence as in central carcinoids, still without a clear preneoplastic lesion.

Neuroendocrine Tumors of the Female Reproductive Tract: A Literature Review

Neuroendocrine tumors of the female reproductive tract are a heterogeneous group of neoplasms that display various histologic findings and biologic behaviors. In this review, the classification and clinicopathologic characteristics of neuroendocrine tumors of the female reproductive tract are described. Differential diagnoses are discussed, especially for non-neuroendocrine tumors showing high-grade nuclei with neuroendocrine differentiation. This review also discusses recent advances in our pathogenetic understanding of these disorders.

The clinical course of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

BACKGROUND

Current understanding of the clinical course of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is poor and based predominantly on small case series. In our clinical experience, we have found that the diagnosis of DIPNECH is frequently delayed because respiratory symptoms are ascribed to other lung conditions. The objectives of this study were to collect and analyze longitudinal clinical data on pulmonary physiology, chest high-resolution CT (HRCT) imaging, and therapies to better delineate the course of disease.

METHODS

We established a cohort of patients (N = 30) with DIPNECH seen at our institution. We used descriptive statistics to summarize cohort characteristics and longitudinal analytic techniques to model FEV1 % predicted (FEV1%) over time.

RESULTS

All subjects were women who presented with long-standing cough and dyspnea. The majority had an FEV1% < 50% at the time of diagnosis. Forty percent were given a diagnosis of asthma as the cause for physiologic obstruction. The mean FEV1% for the entire cohort showed no statistically significant decline over time, but 26% of the subjects experienced a 10% decline in FEV1 within 2 years. Among the pathology samples available for review, 28% (five of 18) had typical carcinoids and 44% had associated constrictive bronchiolitis. We propose clinical diagnostic criteria for DIPNECH that incorporate demographic, pulmonary physiology, HRCT imaging, and transbronchial and surgical lung biopsy data.

CONCLUSIONS

DIPNECH is a female-predominant lung disease manifested by dyspnea and cough, physiologic obstruction, and nodules on HRCT imaging. Additional research is needed to understand the natural history of this disease and validate the proposed diagnostic criteria.

Pulmonary neuroendocrine (carcinoid) tumors: European Neuroendocrine Tumor Society expert consensus and recommendations for best practice for typical and atypical pulmonary carcinoids

BACKGROUND

Pulmonary carcinoids (PCs) are rare tumors. As there is a paucity of randomized studies, this expert consensus document represents an initiative by the European Neuroendocrine Tumor Society to provide guidance on their management.

PATIENTS AND METHODS

Bibliographical searches were carried out in PubMed for the terms 'pulmonary neuroendocrine tumors', 'bronchial neuroendocrine tumors', 'bronchial carcinoid tumors', 'pulmonary carcinoid', 'pulmonary typical/atypical carcinoid', and 'pulmonary carcinoid and diagnosis/treatment/epidemiology/prognosis'. A systematic review of the relevant literature was carried out, followed by expert review.

RESULTS

PCs are well-differentiated neuroendocrine tumors and include low- and intermediate-grade malignant tumors, i.e. typical (TC) and atypical carcinoid (AC), respectively. Contrast CT scan is the diagnostic gold standard for PCs, but pathology examination is mandatory for their correct classification. Somatostatin receptor imaging may visualize nearly 80% of the primary tumors and is most sensitive for metastatic disease. Plasma chromogranin A can be increased in PCs. Surgery is the treatment of choice for PCs with the aim of removing the tumor and preserving as much lung tissue as possible. Resection of metastases should be considered whenever possible with curative intent. Somatostatin analogs are the first-line treatment of carcinoid syndrome and may be considered as first-line systemic antiproliferative treatment in unresectable PCs, particularly of low-grade TC and AC. Locoregional or radiotargeted therapies should be considered for metastatic disease. Systemic chemotherapy is used for progressive PCs, although cytotoxic regimens have demonstrated limited effects with etoposide and platinum combination the most commonly used, however, temozolomide has shown most clinical benefit.

CONCLUSIONS

PCs are complex tumors which require a multidisciplinary approach and long-term follow-up.

Neuroendocrine tumors: beyond the abdomen

Several classification systems for neuroendocrine tumors (NETs) exist, which use variable terminology and criteria for grading and staging. This variability in terminology can cause confusion and difficulty in recognizing which tumors are, in fact, members of this heterogeneous group of malignancies. The largest group of NETs, the gastroenteropancreatic NETs, has been well described and characterized; however, there are less-recognized extra-abdominal NETs that can arise from nearly any organ in the body. In this article, the clinical features and imaging appearances of the extra-abdominal NETs will be reviewed, compared, and contrasted. This diverse group consists of paragangliomas, Merkel cell carcinomas, esthesioneuroblastomas, NETs of the lung, and medullary thyroid carcinomas. Recognition of these tumors as part of the larger group of NETs is important for understanding how best to approach imaging for their diagnosis, staging, and potential treatment. Familiarity with the computed tomographic and magnetic resonance imaging appearances and the role of radionuclide imaging of these heterogeneous groups aids in the correct diagnosis and in treatment planning.

DIPNECH: when to suggest this diagnosis on CT

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an under-recognized disease characterized by proliferation of neuroendocrine cells in the bronchial wall. It is considered a pre-invasive lesion for lung carcinoid tumours and is found in 5.4% of patients undergoing surgical resection for lung carcinoid tumours. Other manifestations of DIPNECH include bronchial obstruction and formation of tumorlets. DIPNECH preferentially affects middle-aged women. Patients are either asymptomatic or present with long-standing dyspnoea due to obstructive syndrome that can be mistaken for asthma. At CT, mosaic attenuation with multiple small nodules is very suggestive of DIPNECH. The aim of this review is to describe DIPNECH-related CT features and correlate them with histology, in order to help radiologists suggest this diagnosis and distinguish DIPNECH from other causes of mosaic perfusion.

Spectrum of pulmonary neuroendocrine proliferations and neoplasms

Neuroendocrine neoplasms are ubiquitous tumors found throughout the body, most commonly in the gastrointestinal tract followed by the thorax. Neuroendocrine cells occur normally in the bronchial and bronchiolar epithelium and may be solitary or may occur in clusters. Although neuroendocrine cell proliferations may be found in association with chronic lung disease, a broad range of neuroendocrine proliferations and neoplasms may occur and exhibit variable biologic behavior. Diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) is a diffuse idiopathic form of neuroendocrine cell hyperplasia and is considered a preinvasive lesion that may give rise to carcinoid tumors. Patients with DIPNECH are typically older women who may be asymptomatic or may present with chronic respiratory symptoms. DIPNECH manifests as multifocal bilateral pulmonary micronodules on expiratory high-resolution computed tomographic (CT) images; the air trapping is secondary to constrictive bronchiolitis. Carcinoid tumors are low-grade malignant neoplasms that typically affect symptomatic children and young adults. Carcinoids manifest as well-defined pulmonary nodules or masses that are often closely related to central bronchi. They may exhibit intrinsic calcification and contrast material enhancement at CT, and patients with carcinoids may have postobstructive atelectasis and pneumonia. Although typical carcinoids are indolent neoplasms and patients have a good prognosis, atypical carcinoids are aggressive malignancies with a propensity for metastasis. Both are optimally treated with complete surgical excision. Large cell neuroendocrine carcinoma and small cell lung cancer are highly aggressive neuroendocrine malignancies that usually affect elderly smokers. These tumors manifest with large peripheral or central pulmonary masses. Local invasion, intrathoracic lymphadenopathy, and distant metastases are frequent at presentation. As a result, affected patients may not be candidates for surgical resection, are often treated with chemotherapy with or without radiation, and have a poor prognosis.

Oxygen, gastrin-releasing Peptide, and pediatric lung disease: life in the balance

Excessive oxygen (O2) can cause tissue injury, scarring, aging, and even death. Our laboratory is studying O2-sensing pulmonary neuroendocrine cells (PNECs) and the PNEC-derived product gastrin-releasing peptide (GRP). Reactive oxygen species (ROS) generated from exposure to hyperoxia, ozone, or ionizing radiation (RT) can induce PNEC degranulation and GRP secretion. PNEC degranulation is also induced by hypoxia, and effects of hypoxia are mediated by free radicals. We have determined that excessive GRP leads to lung injury with acute and chronic inflammation, leading to pulmonary fibrosis (PF), triggered via ROS exposure or by directly treating mice with exogenous GRP. In animal models, GRP-blockade abrogates lung injury, inflammation, and fibrosis. The optimal time frame for GRP-blockade and the key target cell types remain to be determined. The concept of GRP as a mediator of ROS-induced tissue damage represents a paradigm shift about how O2 can cause injury, inflammation, and fibrosis. The host PNEC response in vivo may depend on individual ROS sensing mechanisms and subsequent GRP secretion. Ongoing scientific and clinical investigations promise to further clarify the molecular pathways and clinical relevance of GRP in the pathogenesis of diverse pediatric lung diseases.

Carcinoid tumorlet in pulmonary sequestration with bronchiectasis after breast cancer: A case report

Pulmonary sequestration (PS) is an uncommon lung disease. Carcinoid tumorlets in pulmonary sequestration are extremely rare. This case report presents a rare clinical case of carcinoid tumorlet in pulmonary sequestration with bronchiectasis after breast cancer. A 64-year-old female was diagnosed with infiltrating ductal carcinoma of the left breast in February 2009. Chest computer tomography (CT) revealed a cystic low-density mass of ∼2.5×4.7 cm in the right lower lung field, as well as cystic bronchiectasis in the right lower lobe. A right lower lobectomy was performed. In the surgery, abnormal vessel growth from the mass was found. Therefore, intralobar PS was diagnosed and pathological examination supported the diagnosis. Subsequently, pathological examination identified a carcinoid tumorlet in the PS. This report presents a rare clinical case of PS and bronchiectasis as well as carcinoid tumorlet in PS following diagnosis of breast cancer three years earlier. When a mass is found in the lung of patents with bronchiectasis with a history of breast cancer, aggressive therapy should be considered, since the mass may be a tumor or precancerous lesion.

Molecular and cellular biology of neuroendocrine lung tumors: evidence for separate biological entities

Pulmonary neuroendocrine tumors (NETs) are traditionally described as comprising a spectrum of neoplasms, ranging from low grade typical carcinoids (TCs) via the intermediate grade atypical carcinoids (ACs) to the highly malignant small cell lung cancers (SCLCs) and large cell neuroendocrine carcinomas (LCNECs). Recent data, however, suggests that two categories can be distinguished on basis of molecular and clinical data, i.e. the high grade neuroendocrine (NE) carcinomas and the carcinoid tumors. Bronchial carcinoids and SCLCs may originate from the same pulmonary NE precursor cells, but a precursor lesion has only been observed in association with carcinoids, termed diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. The occurrence of mixed tumors exclusively comprising high grade NE carcinomas also supports a different carcinogenesis for these two groups. Histopathologically, high grade NE lung tumors are characterized by high mitotic and proliferative indices, while carcinoids are defined by maximally 10 mitoses per 2mm(2) (10 high-power fields) and rarely have Ki67-proliferative indices over 10%. High grade NE carcinomas are chemosensitive tumors, although they usually relapse. Surgery is often not an option due to extensive disease at presentation and early metastasis, especially in SCLC. Conversely, carcinoids are often insensitive to chemo- and radiation therapy, but cure can usually be achieved by surgery. A meta-analysis of comparative genomic hybridization studies performed for this review, as well as gene expression profiling data indicates separate clustering of carcinoids and carcinomas. Chromosomal aberrations are much more frequent in carcinomas, except for deletion of 11q, which is involved in the whole spectrum of NE lung tumors. Deletions of chromosome 3p are rare in carcinoids but are a hallmark of the high grade pulmonary NE carcinomas. On the contrary, mutations of the multiple endocrine neoplasia type 1 (MEN1) gene are restricted to carcinoid tumors. Many of the differences between carcinoids and high grade lung NETs can be ascribed to tobacco consumption, which is strongly linked to the occurrence of high grade NE carcinomas. Smoking causes p53 mutations, very frequently present in SCLCs and LCNECs, but rarely in carcinoids. It further results in other early genetic events in SCLCs and LCNECs, such as 3p and 17p deletions. Smoking induces downregulation of E-cadherin and associated epithelial to mesenchymal transition. Also, high grade lung NETs display higher frequencies of aberrations of the Rb pathway, and of the intrinsic and extrinsic apoptotic routes. Carcinoid biology on the other hand is not depending on cigarette smoke intake but rather characterized by aberrations of other specific genetic events, probably including Menin or its targets and interaction partners. This results in a gradual evolution, most likely from proliferating pulmonary NE cells via hyperplasia and tumorlets towards classical carcinoid tumors. We conclude that carcinoids and high grade NE lung carcinomas are separate biological entities and do not comprise one spectrum of pulmonary NETs. This implies the need to reconsider both diagnostic as well as therapeutic approaches for these different groups of malignancies.