Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

Clinical History

A 55-year-old non smoker presented with a 4-month history of mild dyspnoea and wheezing. There was no clinical or serological evidence of infection. She had been previously well and had no relevant past medical history.

Imaging Findings

Posteroanterior and lateral radiograph (figures 1a-b) demonstrates numerous small bilateral nodular type densities. Subsequent HRCT scans (figures 2a-g) confirm the presence of multiple nodular densities (arrows on figures 2d-f) and in addition show occasional areas of mucus plugging (arrows on figure 2g). The coronal HRCT images also suggest a very mild mosaic attenuation pattern (figures 3a-c). The patient later underwent a lung biopsy which showed diffuse proliferation of pulmonary neuroendocrine cells.

Discussion

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an extremely rare pulmonary disorder characterised by a proliferation of neuroendocrine cells within the lungs. It is recognised with increasing frequency [2, 6].

The condition typically presents around the 5th to 7th decade [3, 8]. There is a recognised strong female predilection with women accounting for approximately 90% of cases. Most patients tend to be non-smokers [6]. Many patients are asymptomatic at diagnosis and discovery is made often incidentally on thoracic imaging for an unrelated reason [7]. Some may have symptoms such as an insidious cough, wheezing and/or a slowly progressive dyspnoea [7, 8]. Onset of symptoms may widely range from days to years before diagnosis.

DIPNECH is characterised by a generalised proliferation of scattered single cells, small nodules or linear proliferations of pulmonary neuroendocrine cells. It is sometimes considered a precursor for pulmonary carcinoid tumours and a diagnosis of DIPNECH requires the presence of hyperplasia of airway neuroendocrine cells without invasion beyond the basement membrane [4].

HRCT imaging of the chest can be useful but not definitive in determining the diagnosis.
Various HRCT features have been described, each of which are non specific on their own and not all of them are present in the same case. These include

1. Small lung nodules [2-3, 6] - considered generally a frequent feature
2. Mosaic perfusion pattern [1-3, 8]
3. Mucus plugging [8]
4. Bronchial wall thickening [1, 8]
5. Bronchiectasis [2, 8]
6. Ground-glass changes [2]

The first three of the above mentioned imaging findings were present in this case. Pulmonary function tests can often show an obstructive ventilatory disease [2, 6], which was also present in this case.

The rarity of the condition poses some clinical challenge on establishing treatment and assessing prognosis. Limited studies suggest that the condition can have a variable prognosis ranging from clinical improvement to being stable to progressive clinical deterioration. Various treatment strategies have been described, including systemic and inhaled corticosteroids, bronchodilators, and occasionally lung resection. Some advocate excision of the dominant lesion [5]. However, the main mode of management in the majority of patients tend to be surveillance [4].

This case highlights some of the reported imaging features of DIPNECH, although it is important to remember that findings are not specific and differential diagnosis should be considered. Moreover in some cases - i.e. lung nodules that may mimic malignancy - a tissue diagnosis is almost always required.

Differential Diagnosis List

Final Diagnosis

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

URL:	https://www.eurorad.org/case/10572
DOI:	10.1594/EURORAD/CASE.10572
ISSN:	1563-4086