Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH); a case of multiple pulmonary nodules

Clinical History

This case involves a non-smoking 76-year-old female patient with a 7-year history of persistent cough (occasionally productive) and breathlessness on exertion, with no haemoptysis or weight loss. She underwent a VATs-wedge resection for tissue diagnosis as part of a work-up for suspected pulmonary metastases from an undetermined primary.

Imaging Findings

The patient’s CT chest demonstrated multiple nodules of varying sizes (< 5mm) and mosaicism affecting all lobes of both lungs. No other imaging abnormalities were evident. Her imaging findings are consistent with DIPNECH with tumourlets. This was confirmed with histopathology analysis of CT-guided lung nodule biopsy samples.

Discussion

A. Background
The normal respiratory tract has neuroendocrine cells scattered throughout the tracheo-bronchial epithelium. These cells may proliferate in response to high altitude, cigarette smoking, chronic inflammation and chronic lung diseases [2, 3]. If cell proliferation does not extend beyond the epithelial basement membrane, it is known as DIPNECH (Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia). The described proliferation can form larger clusters of cells known as cell nests. These do extend beyond the basement membrane. If cells nests are <5mm these are known as tumourlets, if >5 mm they are known as carcinoids. These entities commonly co-exist [3].

The most common presentation of DIPNECH is usually of women in their thirties or forties who are non-smokers. [1, 2, 3]. Most are asymptomatic, others have an insidious onset of symptoms including cough, breathlessness, wheezing and chest tightness. Symptom onset may be present between 2 - 25 years prior to diagnosis.

Lung function tests often demonstrate an obstructive pattern and/or obliterative bronchiolitis. [1, 3].

On histopathology, findings include neuroendocrine cell hyperplasia, tumourlets, fibrosis, constrictive bronchiolitis, bronchiolectasis, airway wall thickening and mucus plugging [1].


B. Clinical Perspective
In this case study, the patient demonstrates the typical demographics associated with DIPNECH - a female, non-smoker with insidious onset of symptoms of 7 years. She underwent a VATs wedge resection for tissue diagnosis as part of a work-up for suspected pulmonary metastases from an undetermined primary.


C. Imaging Perspective
The patient’s imaging findings of multiple nodules <5mm and mosaicism are typical of DIPNECH with tumourlets. The definitive diagnosis was made by histopathology.


D. Outcome
More studies are required to adequately determine the natural history of the condition, treatment and prognosis. Some patients remain asymptomatic with stable radiological features; in other cases patients become increasingly symptomatic with progressive radiological features. [1]
Patients with DIPNECH require follow up. If symptomatic, a trial course of inhaled and/or oral steroids has been advocated [1]. For asymptomatic patients, observation with no active treatment is considered. Treatment with steroids may become warranted if the patient becomes symptomatic and/or the radiological features demonstrate progression.


E. Take Home Message, Teaching Points
DIPNECH is a rare and somewhat under-recognised disease. As CT scans are performed with increasing frequency and improving resolution, there is a subsequent increasing number of lung biopsies. As such the number of DIPNECH diagnoses is reportedly increasing, and some knowledge of this condition is useful for the radiologist.

Differential Diagnosis List

Final Diagnosis

Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH)

URL:	https://eurorad.org/case/14430
DOI:	10.1594/EURORAD/CASE.14430
ISSN:	1563-4086