1. A diagnostic imaging apparatus, comprising: a detection unit configured to detect a lesion from a medical image; an interpretation unit configured to acquire a shape feature value by interpreting a shape of the detected lesion in a frequency domain; extract one or more feature points from boundaries of the detected lesion; and adjust a number of or an interval between the feature points to be extracted according to properties of the boundaries of the detected lesion; and a diagnosis unit configured to determine whether the detected lesion is benign or malignant based on the acquired shape feature value.