1974

carcinoma, and it would appear that this tumour is a highly malignant variant of the bronchial carcinoid.6 Less common are the adenoid cystic carcinoma and the mucoepidermoid carcinoma, tumours noted most often in the salivary glands. The adenoid cystic carcinoma, also called the cylindroma, consists of trabeculae, columns, and cords of epithelial cells, some enclosing cystic spaces, which are surrounded by a dense, hyaline stroma. The mucoepidermoid carcinoma contains a mixture of squamous-cell and mucus-secreting glandular elements. A true mucus-4secreting adenoma has also been described, but it is very rare.7 Recently A. D. Turnibull and his colleagues have reviewed 61 cases of bronchial adenoma which had occurred over a period of 43 years.8 These comprised 44 carcinoid tumours, 12 mucoepidermoid carcinomata, and 5 adenoid cystic carcinomata. Most of these tumours occurred in patients between the ages of 40 and 70 years, and while the sex incidence was equal in the carcinoid group there was a male predominance in the other two groups of tumours. None of the cases of carcinoid tumour showed the typical endocrine syndrome. The most conspicuous finding in this series was the high degree of malignancy of the tumours. Only 59W/', of the patients with carcinoid tumour and 600,W of those with adenoid cystic carcinoma survived for five years, while all those with mucoepidermoid carcinoma had died during that period of time. This is especially surprising, as mucoepidermoid carcinoma is usually regarded as the most benign type of bronchial adenoma,7 other than the rare mucus-secreting adenoma, which was not encountered in this series. The observations of Turnbull and his colleagues once again contradict the traditional teaching that the various types of bronchial adenoma behave in a benign fashion and are usually compatible with prolonged survival. The time has surely come to expunge the term bronchial adenoma, and to group the tumours that have been included under this heading as bronchial carcinoids, mucoepidermoid carcinomata, and adenoid cystic carcinomata. While they are certainly less malignant than the usual varieties of lung cancer-the oat-cell carcinoma, adenocarcinoma, and squamous-cell carcinoma-their serious nature must be fully acknowledged.