Atypical bronchial carcinoid tumours

*Departments of Respiratory Medicine, tPathology and $Thoracic and Vascular Surgery, University Hospital Antwerp, Wilrijkstraat 10, 2650 Edegem, Belgium Introduction Atypical carcinoids of the lung are rare neuro- endocrine tumours, which are, according to their histologic characteristics, classified between typical carcinoid and small cell lung carcinoma. We describe three patients in whom, within 2 months, atypical carcinoid of the lung was diagnosed, and a fourth patient whose initial diagnosis of small cell lung carcinoma had to be revised after 5 yr. Probably the incidence of these tumours is underestimated, as their histologic differentiation from typical carcinoid and small cell carcinoma can be difficult. Case Reports