The pleural depression sign is not always malignant, and can sometimes be caused by benign diseases, but is usually more common with malignant diseases. The so-called pleural depression is a triangular or curtain-shaped image seen between a lung lesion and the pleura, usually with the tip of the image pointing toward the lesion and the base located in the pleura. Generally, the pleural depression is formed by the fibrous tissue or scar tissue within the lesion pulling on the pleura, and malignant diseases such as lung cancer are prone to form this image. Benign diseases such as tuberculosis can also pull the pleura and cause the pleural depression sign. Therefore, the clinical appearance of pleural depression sign is not necessarily malignant, and further examination is needed to clarify the cause of this image.