Nondiagnostic CT-guided stereotactic biopsies in a series of 407 cases: influence of CT morphology and operator experience.

Nondiagnostic biopsies were analyzed in a consecutive series of 407 patients undergoing computerized tomography (CT)-guided stereotactic biopsies. These were categorized as either negative biopsies, when normal tissue or nonspecific pathology was found, or inconclusive, when a definitive diagnosis could not be made although representative tissue was obtained. Nineteen biopsies (4.7%) were negative and 10 (2.4%) were inconclusive, giving an overall nondiagnostic biopsy rate of 7.1% (29 of the 407 cases). Suspected neoplastic masses (390 cases) were classified on the basis of their CT morphology into four groups: Group 1 included purely hypodense nonenhancing masses; Group 2 included isodense nonenhancing masses; Group 3 included ring-enhancing masses; and Group 4 included mixed-density enhancing masses. Although a higher proportion of hypodense nonenhancing masses (six of 56, or 10.7%) yielded a negative result, there was no statistically significant difference in the negative biopsy rates for the different CT categories (p = 0.06). The negative biopsy rates for the 6 years of the study, 1987 to 1992 (1987 being an incomplete year) were as follows: 13.3%, 6%, 3.2%, 3%, 5.8%, and 2.7%. There was no significant decrease in the negative biopsy rate as experience with this procedure increased (p = 0.20). A total of eight surgeons independently performed the biopsies. There was no significant difference (p = 0.24) in the negative biopsy rate of the surgeon with the most experience (124 biopsies, 2.4% negative biopsy rate) compared with that of the seven other surgeons combined (283 biopsies; 5.7% negative biopsy rate). These findings suggest that the yield in a stereotactic biopsy is independent of the CT appearance of the mass. Adherence to certain basic principles in patient and target selection will ensure a reasonable percentage of positive yield with stereotactic biopsy procedures even if the surgeon is relatively inexperienced. There does not appear to be a learning curve in the performance of CT-guided stereotactic biopsies. The management of patients with nondiagnostic biopsies is discussed.