Lung neuroendocrine tumours (typical and atypical carcinoid)

Lung neuroendocrine tumours are graded differently from their gut counterparts: the WHO lung classification separates typical carcinoid (fewer than two mitoses per two square millimetres and no necrosis) from atypical carcinoid (two to ten mitoses or foci of necrosis), with Ki-67 used to support the count rather than define it, and places both alongside small-cell and large-cell neuroendocrine carcinoma in a single neuroendocrine group. Most typical carcinoids sit centrally in a main or lobar bronchus and present with cough, wheeze, haemoptysis or recurrent pneumonia behind an obstructed airway; peripheral tumours are found incidentally. A few produce ectopic ACTH and Cushing's syndrome, carcinoid syndrome is uncommon without liver metastases, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia is a rare precursor that seeds multiple tumourlets. About a twentieth arise in patients with MEN1.

Surgery is the treatment for localised disease and usually the cure: lobectomy or a parenchyma-sparing sleeve resection with systematic nodal dissection, with endobronchial resection reserved for patients who cannot tolerate an operation. Adjuvant therapy has no proven benefit and follow-up is prolonged because atypical carcinoids can recur years later. For advanced disease the evidence is thin. RADIANT-4 (Lancet 2016) is the only randomised trial to include lung tumours in numbers: 302 patients with non-functional lung or gastrointestinal neuroendocrine tumours were randomised to everolimus or placebo and progression-free survival lengthened from 3.9 to 11.0 months, and the FDA approved everolimus for lung neuroendocrine tumours in 2016. The phase 2 LUNA trial (2017) tested pasireotide, everolimus and the combination in lung and thymic tumours and found each active, without a randomised comparison against placebo.