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

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

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.

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.