1. A method for medical diagnostics, comprising: receiving three-dimensional (3D) volume data of at least a part of an object; generating two-dimensional (2D) slices including cross-sections of the 3D volume data based on a cross-section cutting direction; classifying a lesion in at least two of the generated 2D slices; calculating confidence levels of results of the classification; selecting a plurality of the at least two 2D slices based on the confidence levels of the results of the classification; and re-classifying a lesion included in the 3D volume data based on at least one of the classification results of the selected 2D slices or the confidence levels of the classification results of the selected 2D slices.