Multifocal neuroendocrine lung tumour is a rare diagnosis. Multiple lung foci of different sizes are usually apparent on chest CT scans. It is assumed that multifocal neuroendocrine lung tumours originally develop from diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). This results in cell aggregations formed by proliferation of neuroendocrine cells that are already physiologically present in the bronchial system. If these cell proliferations break through the bronchial basement membrane, they are considered to constitute tumourlets if they measure ≤ 5 mm and carcinoid tumours if they are larger than 5 mm. The speed of proliferation of the cell hyperplasias appears to vary. Many of the patients are completely asymptomatic, the multifocal neuroendocrine lung tumours being diagnosed by chance. However, other patients complain of breathlessness, reduced physical capacity and cough. There may also be reduction of lung function. In these cases, chest HRCT often reveals peribronchial fibrosis or bronchiectasis in addition to the lung foci. Bronchoscopy is usually not helpful. Surgical lung biopsy is considered to be the diagnostic gold standard. Histological examination typically shows a mixture of cell hyperplasias, tumourlets and carcinoid tumours. There is no consensus on the treatment of multifocal neuroendocrine tumours. Taking the clinical situation and the chest HRCT findings as our starting point, we developed a stepwise approach that is guided by the success of the individual therapeutic procedures. The most favourable prognosis is found in affected people without clinical symptoms whose lung foci all measure less than 5 mm. In these cases the 5-year survival rate is over 90%.
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