NONDIAGNOSTIC CT-GUIDED STEREOTAXIC BIOPSIES IN A SERIES OF 407 CASES- INFLUENCE OF CT MORPHOLOGY AND OPERATOR EXPERIENCE

Nondiagnostic biopsies were analyzed in a consecutive series of 407 pa tients undergoing computerized tomography (CT)-guided stereotactic bio psies. These were categorized as either negative biopsies, when normal tissue or nonspecific pathology was found, or inconclusive, when a de finitive diagnosis could not be made although representative tissue wa s 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 classi fied on the basis of their CT morphology into four groups: Group 1 inc luded 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 proporti on of hypodense nonenhancing masses (six of 56, or 10.7%) yielded a ne gative result, there was no statistically significant difference in th e negative biopsy rates for the different CT categories (p = 0.06). Th e negative biopsy rates for the 6 years of the study, 1987 to 1992 (19 87 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 o f eight surgeons independently performed the biopsies. There was no si gnificant difference (p = 0.24) in the negative biopsy rate of the sur geon with the most experience (124 biopsies, 2.4% negative biopsy rate ) compared with that of the seven other surgeons combined (283 biopsie s; 5.7% negative biopsy rate). These findings suggest that the yield i n a stereotactic biopsy is independent of the CT appearance of the mas s. Adherence to certain basic principles in patient and target selecti on will ensure a reasonable percentage of positive yield with stereota ctic biopsy procedures even if the surgeon is relatively inexperienced . There does not appear to be a learning curve in the performance of C T-guided stereotactic biopsies. The management of patients with nondia gnostic biopsies is discussed.