[The echo-guided fine-needle biopsy of thoracic and abdominal masses].

Five hundred and seventy-two US-guided fine-needle biopsies were performed on 561 patients (1.2 puncture/patient); in two cases only minor complications were observed. The patients were 12 to 86 years old--most of them ranging 40 to 75. In 5.42% of cases FNAB proved inadequate; 1.75% of the diagnoses was questionable, 28.89% was negative, and 63.98% positive. A comparison with histology was possible in 218 cases: 2 false positives and 5 false negatives were observed. The low rate of false-positive findings demonstrates US-guided FNAB to have high positive predictive value. The method had 95% sensitivity, 98.4% specificity and 84.3% accuracy. The high reliability of FNAB depends on the possibility of centering the lesion through the direct US visualization of the needle tip. This characteristic, together with the presence of the cytologist, who immediately evaluates the aspirated material, helps reduce the number of unnecessary biopsies and, consequently, complications.