Possible causes of inconclusive results on CT-guided thoracic and abdominal core biopsies

We sought to determine possible technical causes of inconclusive results on CT-guided core biopsies of lesions suggestive of malignancy and to determine the frequency with which such lesions are eventually found to be malignant. We retrospectively reviewed 116 consecutive CT-guided thoracic and abdominal core biopsies performed with a 20-gauge automatic biopsy system. Biopsy results were conclusive (n = 94) if pathology confirmed malignancy and inconclusive (n = 22) if pathology results were negative for malignancy or were nondiagnostic. Lesion volume, location, number of cores, and biopsy technique (paraxial or coaxial) were compared for the conclusive and inconclusive biopsy results. Malignancy within the group of inconclusive biopsy results was determined from a second biopsy, radiographic follow-up, or surgery. Regression analysis identified only the biopsy method as a significant factor affecting biopsy outcome: The paraxial method was more likely to yield a conclusive result than the coaxial method (p < .002). For the two biopsy methods, lesions had similar volumes, locations, and numbers of cores obtained. For single core biopsies, both methods were equivalent. However, if two or more cores were obtained, a conclusive result was achieved in more than 90% of biopsies with the paraxial method versus 65% for the coaxial method. On follow-up, results of 14 (64%) of 22 inconclusive biopsies were malignant, indicating an overall false-negative rate of 12%. CT-guided core biopsy performed with 20-gauge automatic biopsy systems and the paraxial method will yield conclusive results significantly more often than the coaxial method. In the event of inconclusive results, malignancy will exist often enough to warrant follow-up.