Aetiology of unresolved pneumonia.

Preoperative histological or cytological confirmation of a diagnosis of bronchogenic carcinoma is not always possible, so occasionally non-neoplastic lesions are resected. Of these lesions a significant number are described by pathologists as 'unresolved pneumonia'. We studied the case notes and histopathology of 30 patients from whom lung had been resected and which had been classified as pneumonia. Other non-neoplastic lesions, such as pulmonary infarction, bronchiectasis, and tuberculosis, were excluded. All had a preoperative diagnosis of probable bronchial carcinoma. On review very few appeared to be the consequence of an infective, pneumonic episode. In 11, foreign material was identified, including one typical example of a paraffinoma. Aspiration of foreign material may lead to a localised lesion which simulates carcinoma of the bronchus both clinically and radiographically.