Fine needle aspiration cytology of pulmonary lesions: a reliable diagnostic test

Summary

The objective of this study was to determine the accuracy of image-guided fine needle aspiration cytology (FNAC) in the diagnosis of pulmonary lesions. A retrospective study was undertaken of 286 patients with 288 lesions, who underwent a total of 302 procedures. The FNAC diagnoses were reported as malignant, suspicious, atypical, benign or non-diagnostic. Subsequently the FNAC diagnoses were correlated with either the histological or clinical diagnoses. Of the 288 lesions, 64.6% were reported on FNAC as malignant, 2.1% suspicious, 2.4% atypical, 20.8% benign and 10.1% non-diagnostic. On review of the suspicious, atypical, selected benign cases and non-diagnostic FNAC by an independent pathologist there was agreement with the original FNAC diagnosis in all cases. All of 186 malignant FNAC diagnoses were confirmed malignant either clinically or on subsequent histology. Four of the six suspicious FNAC diagnoses had a malignant outcome, one patient had organising pneumonia on excision biopsy and one was lost to follow up. Six of the seven atypical FNAC diagnoses were confirmed on histology as malignant, while one lesion resolved spontaneously. Fifty-two of 60 benign FNAC diagnoses were confirmed benign either clinically or on histology. Seven of the lesions diagnosed as benign on FNAC were proven to be malignant. One patient with a benign FNAC diagnosis was lost to follow-up. Ten of the 29 non-diagnostic FNAC group were later shown on clinical or histological follow up to be malignant. This study shows that image guided FNAC for the diagnosis of malignant pulmonary lesions has a sensitivity of at least 92% and a specificity of at least 96%. It is a reliable diagnostic test although its accuracy is limited by technical difficulties in obtaining an adequate sample.