Teaching Case

A 59-year-old woman presented with a history of dry cough for 20 years, worsening after eating. She denied fever, weight loss or other complaints.

Among her relevant antecedents, she reported being a former smoker with 35 pack-years of exposure, having ceased for 9 years.

Physical examination showed no abnormalities.

The patient underwent posteroanterior and lateral chest simple radiographs (X-rays) (Figs. 1a and Fig. 1b), which revealed two nodules with soft-tissue radiographic density on pulmonary bases, the left one in the retrocardiac position.

She had a history of a severe allergic reaction to iodinated contrast media, and consequently underwent non-contrast-enhanced computed tomography (CT) (Figs. 2a, Fig. 2b and Fig. 2c) that confirmed the presence of two dominant pulmonary nodules, apparently in contact with the pericardium. Multiple bilateral small pulmonary nodules (smaller than 5 mm) were identified in maximum intensity projection (MIP) reconstructions. Pulmonary parenchyma also presented a mosaic attenuation pattern in association with the previously described nodules, which was better demonstrated at minimum intensity projection (MinIP) reconstructions.

Chest magnetic resonance imaging (MRI) (Figs. 3a-c and Fig. 6) was performed to better characterise the nodules and allowed to exclude pericardial invasion, also confirming their suspicious characteristics for neoplasia, such as restriction on DWI and marked enhancement by the paramagnetic agent.

Background: Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a condition characterised by diffuse hyperplasia and distribution of neuroendocrine cell aggregates throughout the respiratory tract (Figs. 4a and Fig. 4b). These cell aggregates present as a histological spectrum: neuroendocrine cell hyperplasia when smaller than 5 mm and do not invade the basement membrane, tumourlets when still smaller than 5 mm, but are associated with invasion of the basement membrane or ‘carcinoids’ if larger than 5 mm (Fig. 5) [1].

Clinical perspective: DIPNECH usually occurs in women between 50 and 70 years of age, most commonly asymptomatic. However, it can manifest clinically as chronic cough and/or dyspnoea associated with obstructive pulmonary function test, findings that are often erroneously attributed to asthma or COPD [1,2].

Imaging perspective: DIPNECH must be considered a rare differential diagnosis for the lungs’ mosaic attenuation pattern, especially when in association with multiple pulmonary nodules. However, a definitive diagnosis should always be histopathological [1,3]. In the case here described, the patient underwent pulmonary segmentectomies to remove both dominant pulmonary nodules, which confirmed the diagnosis of two carcinoid tumours in association with DIPNECH.

Outcome: Due to its rarity, so far there are no protocols that define the better conduct or follow-up of these patients with DIPNECH, however, correct diagnosis is essential, since symptomatic patients benefit from the use of specific drugs such as somatostatin analogs and should have periodic imaging follow-up, due to the increased risk of developing carcinoid tumours [2].

Take home message: Although rare, DIPNECH should be a differential diagnosis for patients with parenchyma’s mosaic attenuation pattern, especially when associated to multiple pulmonary nodules on imaging. With the advancement in quality of imaging methods and an increasing number of exams performed, the radiologist assumes a primary role in the diagnosis, management, and follow-up of patients with DIPNECH.

 Written informed patient consent for publication has been obtained.