Background-Screening Barrett's oesophagus is controversial owing to a large variation in the reported incidence ofneoplastic change and lack of evidence that screening improves tumour prognosis. Conclusions-The cost of screening for Barrett's cancer is high but may be justified on the basis of the high incidence of detecting early stage disease.

Conventional histology and immunoperoxidase staining for fibrin, immunoglobulins, and complement components were used to look for evidence of cutaneous vasculitis and immune complex deposition in Sweet's syndrome. These features were not identified in any of the 15 cases studied. The lack of any vasculitis emphasises the distinctive character of Sweet's syndrome when compared with certain spontaneous and experimentally induced inflammatory skin lesions, and may imply a similarly distinctive pathogenesis.

Proliferating cell nuclear antigen (PCNA) is expressed in cells in the cell cycle and has been studied as a marker of proliferation in lung and other tumours. We have noted immunocytochemical differences in PCNA expression between normal and neoplastic bronchial cells. As bronchial dysplasia is considered preneoplastic, we have examined PCNA expression in this condition. PCNA staining in 47 cases of bronchial dysplasia and 32 samples of normal bronchial epithelium was compared. Of the dysplasias, three were mild, 11 moderate, and 33 severe. A significant increase in PCNA counts over normal epithelium was seen only in moderate and severe dysplasias. In dysplasia, mitotic indices showed a significant positive correlation with the percentage of PCNA-positive cells. We conclude that in moderate and severe dysplasias there is an increase in the number of cells expressing PCNA and undergoing division, indicating abnormal growth control.

S_mmary Bronchial epithelial dysplasia is thought to be a premalignant stage in the evolution of lung cancers. Using the CM-1 polyclonal antibody, we have examined the expression of the p53 protein in a larger series of bronchial dysplasias (n = 60) than hitherto investigated. The p53 protein was detected in 14% of mild, 25% of moderate and 59% of severe dysplasias; increased p53 expression correlated with the severity of dysplasia. p53-positive dysplasias had greater PCNA indices than p53-negative dysplasias. p53 expression in dysplastic tissues was compared with that in two groups of histologically normal epithelium: 14 bronchial biopsies from non-cancer patients of which all but one were negative and 32 bronchial margins from resecied carcinomas, of which 17 showed infrequent solitary cells with p53-positive nuclei in predominantly basal locations scattered throughout the epithelium. These results for resection margins were confirmed by use of a second antibody, DO-1. Sixty-nine per cent of the corresponding carcinomas were p53 positive, but in 15 cases the p53 reactivity differed from resection margins. No correlation between p53 expression and any of the clinicopathological characteristics of these tumours was found. This study supports the observation that abnormal p53 expression may be an early but not obligatory event in malignant transformation in lung.