Preoperative histological classification of primary lung cancer: accuracy of diagnosis and use of the non-small cell category

Aims-To compare the preoperative classification of lung carcinoma made on c ytological and histological specimens with the postoperative classification made on the resected specimen. In addition, to find out how often the term "non-small cell lung cancer, not otherwise specified" (NSCLC) was used, an d in such cases to note the final diagnosis. Methods-Between 1991 and 1995, 303 patients had a lung resection in Aberdee n for primary carcinoma. For each patient, the departmental records were ex amined for preoperative specimens (cytological and histological). A note wa s made of whether each specimen was positive or negative for malignancy and , if positive, what the cell type was. Where patients had more than one sam ple submitted, the most specific result was taken. Results-Fifty four per cent of patients had a correct specific preoperative diagnosis of malignancy, whereas 34% were labelled as NSCLC. Patients with squamous carcinoma were more likely to have a diagnosis of malignancy (88% ) that was specifically correct (75%). Patients who had adenocarcinoma were less likely to have a preoperative diagnosis of malignancy (64%) that was specifically correct (35%). For those in whom a diagnosis of NSCLC was made , 55% turned out to have adenocarcinoma whereas 24% had squamous carcinoma. Conclusions-By adhering strictly to criteria, a high accuracy of diagnosis can be achieved for squamous carcinoma, but the diagnosis of adenocarcinoma seems to be more of a challenge. NSCLC is a useful and appropriate classif ication, the use of which reduces the rate of inaccurate specific diagnosis . There are occasions when pathologists can provide a more accurate diagnos is by being less precise.