1. A medical image processing apparatus, comprising: a medical image obtaining unit configured to obtain a medical image representing a subject; an anatomical information extraction unit configured to extract a lung contour from the obtained medical image, said lung contour finely showing a depressed shape portion therein; a depressed portion detection unit configured to compare the extracted lung contour with a comparison contour showing a shape of a lung smoother than the lung contour and that detects a different portion bet en the extracted lung contour and the comparison contour as a depressed portion of the extracted lung, wherein the comparison contour is obtained from the medical image by deforming an active curve having an initial shape in the lung a plurality of times until given conditions are met according to a certain deformation trend; and a pleural plaque candidate detection unit configured to determine the detected depressed portion as a first pleural plaque candidate.