Number of ultrasound-guided biopsy sections required for quantitative analysis. Evaluation of the number of ultrasound-guided biopsy sections required for quantitative analyses of CD68, CD3 and CD20 cells. Reduction in the percentage mean difference can be obtained by studying 2.5 mm2 from an increasing number of sections. Arrows, number of sections that allow one to achieve a percentage mean difference lower than 10%. x axis, number of sections studied; y axis, percentage mean difference.