Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an extremely rare pulmonary disorder at the benign end of the neuroendocrine cells proliferation spectrum. It is mainly seen in non-smoker middle-age females with a history of chronic cough or asthma. On imaging, it is characterised by several nodules and extensive mosaic attenuation. It is, however, recognised with increasing frequency.

Epidemiology

There may be an increased female predilection ³. Most patients tend to be non-smokers and between 50 and 70 years old.

Clinical presentation

Most are asymptomatic, where discovery is made incidentally on thoracic imaging for an unrelated reason. Some, however, may present with symptoms such as an insidious cough or a slowly progressive dyspnoea ⁷.

Pathology

ItDIPNECH is characterised by a generalised proliferationdiffuse neurendocrine cell hyperplasia of the peripheral airways, forming scattered single cells, small nodules, or linear proliferations of pulmonary neuroendocrine cells (enterochromaffin cells, "Kulchitsky cells") ⁹confined to the airway mucosa. It may be associated with fibrosis or chronic inflammation. Therefore, DIPNECH may cause bronchiolar occlusion and constrictive bronchiolitis.

It is sometimes considered to be a precursor to the development of carcinoid tumorlets (nodular aggregates that measure less than 5 mm and invade the adjacent basement membrane) or carcinoid tumor (cells aggregates of 5 mm or more and demonstrate invasive growth.).

A reactive pulmonary carcinoid tumoursneuroendocrine cell hyperplasia related to hypoxia or lung injury have also been described and it considered a diferent entity. DIPNECH is reserved only for cases in which the hyperplasia is an idiophatic condition.

Radiographic features

CT

Various features have described, each of whichThe constrictive bronchiolitis is non-specific on their ownresponsible for the radiographic features. These include:

• small lung nodules: considered a generally frequent feature ^3-4
• ground-glass changes³
• DIPNECH manifests as multifocal bilateral pulmonary micronodules (cells clusters) and extensive mosaic perfusion patternattenuation^6-7: due to air trapping
• bronchial and constrictive bronchiolitis on expiratory CT images. Bronchial wall nodular thickening⁷
• (cell clusters), mucus plugging
• and bronchiectasis^3,7

Treatment and prognosis

The rarity of the condition poses some clinical challenge in establishing treatment and assessing prognosis. Limited studies suggest that the condition can have a variable prognosis ranging from clinical improvement to being stable to rare clinical deterioration⁵

In many centers the management of patients with DIPNECH is close surveillance and in case of carcinoid tumor formation, lung surgery. Various

Other treatment strategies have been described which include systemic and inhaled corticosteroids, bronchodilators, somatostatin analogs and lung resectioninterferon.

History and etymology

The first clinical series of six cases describing DIPNECH was published by Aguayo et al. in 1992.