Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia: an unusual cause of cyclical ectopic adrenocorticotrophic syndrome

We present the case of a 73-year-old woman who presented with clinical features of Cushing's syndrome, confirmed biochemically with elevated levels of cortisol and adrenocorticotrophic hormone (ACTH). Petrosal venous sampling showed no ACTH gradient and MRI of pituitary was normal, suggesting ectopic ACTH production. In the course of further investigations, a thoracic CT was carried out to look for evidence of bronchial neoplasm. Although there was no discrete tumour identified, CT revealed widespread fine nodularity in the right middle and lower lobe. Subsequent trans-bronchial and video-assisted thorascopic biopsy showed pulmonary tumourlets and two typical carcinoid tumours on a background of diffuse idiopathic pulmonary neuroendocrine cell neoplasia (DIPNECH). We describe the clinical, radiological and histological features of this rare condition.