Diffuse pulmonary neuroendocrine cell hyperplasia: radiologic and clinical features

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.

Long-Term Imaging Follow-Up in DIPNECH: Multicenter Experience

Diffuse pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare pre-invasive disease whose pathophysiology remains unclear. We aimed to assess long-term evolution in imaging of DIPNECH, in order to propose follow-up recommendations. Patients with histologically confirmed DIPNECH from four centers, evaluated between 2001 and 2020, were enrolled if they had at least two available chest computed tomography (CT) exams performed at least 24 months apart. CT exams were analyzed for the presence and the evolution of DIPNECH-related CT findings. Twenty-seven patients, mostly of female gender (n = 25/27; 93%) were included. Longitudinal follow-up over a median 63-month duration (IQR: 31–80 months) demonstrated an increase in the size of lung nodules in 19 patients (19/27, 70%) and the occurrence of metastatic spread in three patients (3/27, 11%). The metastatic spread was limited to mediastinal lymph nodes in one patient, whereas the other two patients had both lymph node and distant metastases. The mean time interval between baseline CT scan and metastatic spread was 70 months (14, 74 and 123 months). Therefore, long-term annual imaging follow-up of DIPNECH might be appropriate to encompass the heterogeneous longitudinal behavior of this disease.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia: DIPNECH

PURPOSE OF REVIEW

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare premalignant condition. Over the past decade, there has been increased recognition and reporting of DIPNECH in the literature. Currently, our understanding is that DIPNECH has a predilection to nonsmoking females around their sixth decade of life. The patients usually present with chronic cough, dyspnea, and computed tomography (CT) showing multifocal pulmonary nodules with associated mosaic attenuation. The clinic history is largely driven by constrictive obliterative bronchiolitis, which typically has an indolent course with progressive respiratory decline and difficult to treat symptoms.

RECENT FINDINGS

DIPNECH has been found to be associated with carcinoid tumors. Recent data has found that symptomatic DIPNECH patients respond to somatostatin analog (SSA). SSAs provide improvement in symptoms and pulmonary function tests. According to small studies and case series SSAs can be used in conjunction with steroids and bronchodilators for the treatment of respiratory symptoms.

SUMMARY

DINPNECH is a premalignant condition that can transform into carcinoid tumors. Although the recent data suggest the potential efficacy of SSA, further studies are needed to validate such results in prospective fashion in addition to investigating other therapeutic agents.

[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: Imaging and Clinical Features of a Frequently Delayed Diagnosis

OBJECTIVE. The purpose of this study was to assess features of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) on CT, clinical presentation, and delays in radiologic and clinical diagnosis in a series of 32 patients. MATERIALS AND METHODS. Medical records of patients with DIPNECH from the years 2000-2017 were obtained from an institutional data warehouse. Inclusion criteria were an available CT examination and either a pathologic diagnosis of DIPNECH or pathologic findings of multiple carcinoid tumorlets or carcinoid tumor with CT features suggesting DIPNECH. Two thoracic radiologists with 10 and 14 years of experience reviewed CT examinations and scored cases in consensus. RESULTS. All 32 patients were women, and most had never smoked (69%). The mean age at presentation was 61 years. Symptoms included chronic cough (59%) or dyspnea (28%), and the initial clinical diagnosis was asthma in 41%. DIPNECH was clinically suspected at presentation in only one case and was mentioned by the interpreting radiologist in only 31% of cases. CT characteristics included numerous nodules with a lower zone and peribronchiolar predominance, mosaic attenuation, and nodular bronchial wall thickening. Number of nodules at least 5 mm in diameter showed strong inverse correlations with the percentage predicted for both forced vital capacity and forced expiratory volume in 1 second and a moderate inverse correlation with total lung capacity percentage predicted. In cases with a follow-up CT interval of 3 years or longer, 85% of patients showed an increase in size of the largest nodule, and 70% had an increase in size in multiple nodules. CONCLUSION. Many cases of DIPNECH are originally missed or misdiagnosed by radiologists and clinicians. Awareness of the typical clinical and imaging features of DIPNECH may prompt earlier diagnosis of this condition.

Primary lung neoplasms presenting as multiple synchronous lung nodules

Multiple synchronous lung nodules are frequently encountered on computed tomography (CT) scanning of the chest and are most commonly either non-neoplastic or metastases from a known primary malignancy. The finding may initiate a search for primary malignancy elsewhere in the body. An exception to this rule, however, is a class of rare primary lung neoplasms that originate from epithelial (pneumocytes and neuroendocrine), mesenchymal (vascular and meningothelial) and lymphoid tissues of the lung. While these rare neoplasms also present as multiple synchronous unilateral or bilateral lung nodules on chest CT, they are often overlooked in favour of more common causes of multiple lung nodules. The correct diagnosis may be suggested by a multidisciplinary team and established on biopsy, performed either as part of routine diagnostic work-up or staging for malignancy. In this review, we discuss clinical presentations, imaging features, pathology findings and subsequent management of these rare primary neoplasms of the lung.

Pulmonary Neuroendocrine Tumors

Pulmonary neuroendocrine tumors represent a morphologic spectrum of tumors from the well-differentiated typical carcinoid tumor, to the intermediate-grade atypical carcinoid tumor, to the high-grade neuroendocrine carcinomas composed of small-cell carcinoma and large-cell neuroendocrine carcinoma. The addition of immunohistochemistry in diagnostics is helpful and often essential, especially in the classification of large-cell neuroendocrine carcinoma. The importance of the intermediate-grade atypical carcinoid group is underscored by the impact of this diagnosis on therapy. The distinction of pulmonary small-cell carcinoma from large-cell neuroendocrine carcinoma, despite both being in the high-grade group, is of relevance to the therapeutic approach to these tumor types.

A typical carcinoid tumor of the lung presenting with pure persistent ground-glass opacity on high-resolution computed tomography: a case report

Pure ground-glass opacity nodules (p-GGN) on high-resolution computed tomography (HRCT) generally have been considering typically associated with adenocarcinoma with less invasive nature. We herein reported a patient presenting focal p-GGN on middle lobe of the right lung who underwent surgical resection with its pathological diagnosis turned out to be typical carcinoid tumor.

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.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia syndrome

The term diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) may be used to describe a clinico-pathological syndrome, as well as an incidental finding on histological examination, although there are obvious differences between these two scenarios. According to the World Health Organization, the definition of DIPNECH is purely histological. However, DIPNECH encompasses symptomatic patients with airway disease, as well as asymptomatic patients with neuroendocrine cell hyperplasia associated with multiple tumourlets/carcinoid tumours. DIPNECH is also considered a pre-neoplastic lesion in the spectrum of pulmonary neuroendocrine tumours, because it is commonly found in patients with peripheral carcinoid tumours.

In this review, we summarise clinical, physiological, radiological and histological features of DIPNECH and critically discuss recently proposed diagnostic criteria. In addition, we propose that the term “DIPNECH syndrome” be used to indicate a sufficiently distinct patient subgroup characterised by respiratory symptoms, airflow obstruction, mosaic attenuation with air trapping on chest imaging and constrictive obliterative bronchiolitis, often with nodular proliferation of neuroendocrine cells with/without tumourlets/carcinoid tumours on histology. Surgical lung biopsy is the diagnostic gold standard. However, in the appropriate clinical and radiological setting, transbronchial lung biopsy may also allow a confident diagnosis of DIPNECH syndrome.

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.

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.

The spectrum of changes in adults with multifocal pulmonary neuroendocrine proliferations: what is the minimum set of pathologic criteria to diagnose DIPNECH?

Diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) can be difficult to diagnose in resections for lung tumors and other conditions, as variable diagnostic criteria and definitions of "diffuse" and/or "idiopathic" have been used in the literature. We reviewed 70 consecutive lung wedge biopsies and resection specimens with multifocal neuroendocrine cell proliferations (NEP) including neuroendocrine cell hyperplasia (NECH) and/or carcinoid tumorlets to identify pathologic findings significantly associated with neuroendocrine neoplasms. The presence of pathologic changes other than NEP (eg, interstitial fibrosis, bronchiectasis, others) and the number of tumorlets were recorded to identify "idiopathic NEP." Cases were classified into 4 groups: A: NECH only, B: >1 tumorlet without NECH, C: NECH + 2 tumorlets, and D: NECH + >2 tumorlets. Proportions of neuroendocrine neoplasms and presence/absence of pathologic changes other than NEP were compared by group with χ(2) statistics. Carcinoids were seen in 8 (22.8%) of 35 and in 21 (72.4%) of 29 groups B and D cases, respectively. Of the 21 group D carcinoids, 18 (85.7%) lacked other associated pathologic changes, and the incidence of these tumors in this group was significantly higher (P < .001) than in group B. Three high-grade neuroendocrine carcinomas were seen, 1 each in groups A to C. Because group D cases had a significantly higher proportion of carcinoid tumors and a significant lack of association with conditions that could result in secondary NECH, the presence of multifocal NECH combined with 3 or more carcinoid tumorlets is proposed as minimum pathologic criteria for the diagnosis of DIPNECH.

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.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia with a central and peripheral carcinoid and multiple tumorlets: a case report emphasizing the role of neuropeptide hormones and human gonadotropin-alpha

We report a case of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). We performed immunohistochemical analysis of 17 neuropeptides and human gonadotropin-alpha (hCGα), a trophoblastic peptide that promotes the proliferation of neuroendocrine cells. A 51-year-old woman with no history of smoking was found to have a nodule in the right middle lobe. Upon examination, the nodule was found to comprise diffuse linear and nodular neuroendocrine cell hyperplasia (NECH), numerous pulmonary tumorlets merging with one peripheral carcinoid, and an additional central carcinoid. Immunohistochemical analysis revealed diffuse but intense expression of the general neuroendocrine markers CD56, synaptophysin, and chromogranin A, together with gastrin-releasing peptide (GRP), calcitonin, and hCGα throughout the carcinoids, tumorlets, and NECH. Positive staining was also noted for adrenocorticotropic hormone, corticotropin-releasing hormone, met-enkephalin, vasoactive intestinal polypeptide, neurotensin, and growth hormone-releasing hormone in a few isolated cells of the carcinoids and the tumorlets, but staining for these proteins was entirely negative in the NECH lesions. The presence of these neuropeptides in neuroendocrine tumors might explain the presence of neuropeptide-producing tumors of the lungs, cases of which have been reported over the last 30 years. The preoperative serum proGRP level was high but returned to normal after surgical intervention, indicating that GRP was produced and secreted by carcinoids, tumorlets, and/or NECH lesions. It is also probable that neuroendocrine cells secreted GRP into the interstitium in a paracrine manner, leading to the development of dense fibrosis around the tumorlets. During the preoperative and postoperative periods, no evidence of bronchiolitis obliterans was noted, in contrast to some previously reported cases of DIPNECH.

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

OBJECTIVE

The objectives of this article are to review the radiologic, pathologic, and clinical features of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, tumorlet, and carcinoids and to discuss the possible role of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia and tumorlet in the development of carcinoids.

CONCLUSION

Given the potential significant morbidity of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia and its neoplastic counterparts, it is important to understand and recognize these disease entities. A conceptual continuum of these neuroendocrine entities is suggested.

Hiperplasia de células neuroendócrinas pulmonares difusas com obstrução ao fluxo aéreo

A hiperplasia de células neuroendócrinas pulmonares difusas com obstrução ao fluxo aéreo é uma lesão pulmonar rara. Todos os casos publicados foram diagnosticados por biópsia pulmonar cirúrgica. Apenas três casos relatados apresentavam opacidades intersticiais difusas na TCAR. Nós relatamos três casos adicionais desta entidade. Todos eram mulheres, com obstrução leve ou moderada ao fluxo aéreo. No primeiro caso, uma biópsia transbrônquica, associada com dados de imagem foram considerados suficientes para o diagnóstico. Um padrão em mosaico foi observado nos três casos, mas no terceiro um infiltrado pulmonar difuso foi também observado. Em casos muito raros, o aspecto na TCAR pode simular aquele encontrado em outras doenças pulmonares intersticiais.

[A 74-year-old female patient with histologically proven carcinoid of the lungs and pulmonary mosaic pattern]

Diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) can be idiopathic or reactive to chronic airway disease, then termed pulmonary neuroendocrine cell hyperplasia (PNECH). DIPNECH can be complicated by obliterative bronchiolitis and is presumably often misdiagnosed because the clinical symptoms are unspecific, the entity is relatively unknown and high-resolution computed tomography (HRCT) in inspiration and expiration is necessary for the diagnosis. However, the HRCT findings of air-trapping in combination with nodules are very characteristic and should raise suspicion of this entity. DIPNECH is thought to be a precursor of tumorlets and carcinoids and usually runs a benign course. The diagnosis is confirmed by histology.

Padrões tomográficos das doenças intersticiais pulmonares difusas com correlação clínica e patológica

A tomografia de alta resolução (TCAR) é a técnica de imagem radiológica que reflete mais de perto as alterações da estrutura pulmonar. Os vários achados tomográficos podem ser combinados para formar padrões típicos. Estes, conjuntamente com a distribuição anatômica dos achados, e com os dados clínicos, podem estreitar o diagnóstico das doenças intersticiais pulmonares difusas, e em vários casos sugerir o diagnóstico correto com alto grau de acurácia. Os padrões mais comuns das doenças intersticiais pulmonares difusas na TCAR são o nodular, linear e reticular, lesões císticas, opacidades em vidro fosco e consolidações. Este artigo revisa as correlações entre os padrões tomográficos na TCAR e os achados patológicos e resume as causas mais comuns e os métodos de investigação para se atingir um diagnóstico nas doenças pulmonares crônicas difusas mais comuns.

Pulmonary Preneoplasia

Context.—Improved screening techniques for lung cancer have resulted in detection of lesions that are considered to represent precursors of invasive lung carcinomas. These lesions may cause a diagnostic dilemma particularly on small biopsy or cytology specimens. Ancillary studies are usually not helpful, and diagnosis is based on morphology alone. Recognition of these lesions is very important to prevent potential diagnostic mistakes that may result in inadequate patient management. Future molecular studies may provide clinically useful diagnostic and prognostic gene markers.

Objective.—To review currently proposed morphologic criteria for precursor lesions of non–small cell lung carcinomas including squamous dysplasias, atypical adenomatous hyperplasia, and diffuse idiopathic neuroendocrine cell hyperplasia. Major molecular abnormalities are briefly discussed.

Data Sources.—Published literature and recent World Health Organization classification of lung tumors.

Conclusions.—Practicing surgical pathologists must be familiar with morphology of recognized pulmonary preneoplastic lesions that are more frequently detected radiographically and subjected to diagnostic procedures. Future understanding of underlying molecular abnormalities associated with progression of these lesions into invasive lung carcinoma may result in a development of molecular assays with potential diagnostic and prognostic importance.

Imaging of small airways disease and chronic obstructive pulmonary disease

CT is a useful tool for identification of small airways diseases, and it can be used to classify these entities into inflammatory and constrictive bronchiolitis. Inflammatory forms of bronchiolitis include cellular bronchiolitis (usually caused by infection or aspiration), respiratory bronchiolitis, panbronchiolitis, and follicular bronchiolitis. Constrictive bronchiolitis may be caused by previous infection, toxic inhalation, collagen vascular disease, or transplantation. CT also helps categorize chronic obstructive pulmonary disease into emphysema predominant and airway predominant forms.

Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is a condition characterized by inflammation and fibrosis of the bronchiolar walls resulting in narrowing or obliteration of the bronchiolar lumen. The most common causes are childhood lower respiratory tract infection, hematopoietic stem cell or lung and heart-lung transplantation, and toxic fume inhalation. The most frequent clinical manifestations are progressive dyspnea and dry cough. Pulmonary function tests demonstrate airflow obstruction and air trapping. Radiographic manifestations include reduction of the peripheral vascular markings, increased lung lucency, and overinflation. The chest radiograph, however, is often normal. High-resolution CT is currently the imaging modality of choice in the assessment of patients with suspected or proven OB. The characteristic findings on high-resolution CT consist of areas of decreased attenuation and vascularity (mosaic perfusion pattern) on inspiratory scans and air trapping on expiratory scans. Other CT findings of OB include bronchiectasis and bronchiolectasis, bronchial wall thickening, small centrilobular nodules, and three-in-bud opacities. Recent studies suggest that hyperpolarized ³He-enhanced magnetic resonance imaging may allow earlier recognition of obstructive airway disease and therefore may be useful in the diagnosis and follow-up of patients with OB.

Challenges in pulmonary fibrosis. 2: Bronchiolocentric fibrosis

Bronchiolocentric fibrosis is essentially represented by the pathological pattern of constrictive fibrotic bronchiolitis obliterans. The corresponding clinical condition (obliterative bronchiolitis) is characterised by dyspnoea, airflow obstruction at lung function testing and air trapping with characteristic mosaic features on expiratory high resolution CT scans. Bronchiolitis obliterans may result from many causes including acute diffuse bronchiolar damage after inhalation of toxic gases or fumes, alloimmune chronic processes after lung or haematopoietic stem cell transplantation, or connective tissue disease (especially rheumatoid arthritis). Airway-centred interstitial fibrosis and bronchiolar metaplasia are other features of bronchiolocentric fibrosis.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia is an extremely rare pulmonary lesion, with only 39 cases reported in the literature. We report an additional case and review the literature. The patient is a 41-year-old man with a 5-year history of progressive dyspnea, cough, and wheezing. He was initially diagnosed as having bronchial asthma but did not respond to treatment of bronchodilators and inhaled steroids. Pulmonary function tests showed airflow obstruction. Chest computed tomography revealed a mosaic pattern of air trapping and thickening of bronchial walls. Open lung biopsy showed diffuse proliferation of pulmonary neuroendocrine cells within the bronchiolar epithelium, often bulging into or obliterating the bronchiolar lumen. These cells also breached the basement membrane, forming tumorlets. There was prominent peribronchiolar fibrosis and obliterative bronchiolitis. The pathologic evaluation of lung tissue is currently the gold standard in making a definitive diagnosis of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, and all the reported cases were diagnosed by either open lung biopsy or lobectomy.

Significance of multiple carcinoid tumors and tumorlets in surgical lung specimens: analysis of 28 patients

BACKGROUND

The clinical significance of multiple carcinoid tumorlets in surgical lung specimens has not been systematically analyzed. We reviewed our experience to determine the range of clinical circumstances associated with this finding.

METHODS

We reviewed clinical records, available imaging, and pathology materials from patients evaluated at Mayo Clinic Rochester (from 1987 to 2000) with two or more carcinoid tumors or tumorlets in lung specimens.

RESULTS

Twenty-eight of 294 patients with a diagnosis of carcinoid tumor or tumorlet had two or more lesions. Twenty-six patients (93%) were women; mean age was 65 years. Patients were categorized into three groups: multiple nodules (n = 17), solitary lung nodules on preoperative imaging (n = 7), and airflow limitation (n = 4). Approximately half of patients with multiple nodules had respiratory complaints; two patients had Cushing syndrome. Ten patients (58.8%) were suspected of having pulmonary metastases, including 7 patients with previously diagnosed malignancies. Intrathoracic lymph node metastases were present in three patients, none of whom had recurrent disease. One patient had a carcinoid tumor resected 8 years later. Extrathoracic metastases developed in another patient 3 years after presentation, and the patient was alive with disease 2 years later. Only one patient with airflow limitation had a syndrome resembling diffuse idiopathic pulmonary neuroendocrine cell hyperplasia.

CONCLUSIONS

Our series represents the largest compilation of multiple carcinoid tumors or tumorlets. Our analysis reveals that multiple carcinoid tumors or tumorlets occur most commonly in patients with multiple nodules resembling metastatic disease. Significant airflow limitation is rare. Long-term survival is excellent, although patients have persistent disease.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia: an under-recognised spectrum of disease

AIMS AND METHODS

A review was undertaken of 19 patients diagnosed with diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) between 1992 and 2006.

RESULTS

Most patients were women (n = 15) and non-smokers (n = 16). Clinical presentation was either with symptomatic pulmonary disease (group 1; n = 9) or as an incidental finding during investigation for another disorder, most frequently malignant disease (group 2; n = 10). In group 1, cough and dyspnoea were the most frequent symptoms, with an average duration of 8.6 years before diagnosis. Both groups showed mainly stable disease without treatment, although one patient progressed to severe airflow obstruction and one was diagnosed at single lung transplantation. Mosaicism with nodule(s) was the typical pattern of DIPNECH on high-resolution computed tomography, but one case had normal imaging despite airflow obstruction. Lung function tests showed obstructive (n = 8), mixed (n = 3) or normal (n = 5, all group 2) physiology. Two patients underwent a bronchoalveolar lavage and showed a lymphocytosis (30%) with mild chronic bronchiolitis being seen in all biopsies. Tumourlets and associated typical carcinoids (n = 9) showed weak positivity for thyroid transcription factor-1. Three patients had atypical carcinoids, one with multiple endocrine neoplasia type 1 syndrome.

CONCLUSIONS

DIPNECH is being increasingly recognised, probably because of an increase in the usage and accuracy of investigative imaging and increased awareness of the entity. Most cases remain stable over many years independent of the mode of presentation, although a few patients progress to severe airflow obstruction.

Diffuse Idiopathic Neuroendocrine Cell Hyperplasia Causing Severe Airway Obstruction in a Patient with a Carcinoid Tumor

We report a 57-year-old female with severe airway obstruction who underwent resection of a tumor of unknown dignity during lung volume reduction surgery. The nodule consisted of a well-differentiated neuroendocrine tumor (carcinoid), and severe chronic obstructive lung disease was due to diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, a very rare cause of obliterative bronchiolitis. Radionuclide ablative therapy of the neuroendocrine tissue was considered but not found to be feasible due to a low lung/background ratio of the radiotracer.

Radiologic and pathologic features of bronchiolitis

OBJECTIVE

The purpose of this article is to describe and illustrate the clinical, pathologic, and imaging features of the inflammatory and fibrotic forms of bronchiolitis. The CT features presented in this article represent the typical features associated with each entity.

CONCLUSION

Direct signs of bronchiolitis include centrilobular nodules and tree-in-bud pattern. Indirect signs include mosaic attenuation and air trapping. Although classic examples of each entity exist, there can be substantial overlap in the appearances, and distinguishing among these entities is not always possible. When high-resolution CT features overlap, clinical details will usually help to narrow the differential diagnosis.