Nowadays, patients are generally more educated and will have some understanding of certain disease phenomena. However, sometimes, a certain sign related to tumor can be directly associated or 100% correct by some patients, which is ridiculous. “Calcification” is one such thing! Calcification refers to the presence of calcium in tissues other than bones and teeth (which are rich in calcium). With the widespread use of ultrasound and advanced research, the diagnostic level of ultrasound for breast and thyroid tumors is gradually improving. The presence of “calcification”, as well as the size, shape and quantity of “calcification”, are important indications to distinguish benign and malignant tumors. In fact, the so-called “calcification” refers to the presence of calcium in tissues other than bones and teeth (which are rich in calcium), which indicates a systemic or localized disease in the body. For example, calcification in the lungs left after healing from tuberculosis; breast or thyroid tumors or inflammation can cause localized calcification: prostate calcification is mostly associated with inflammation; hyperparathyroidism causes calcium deposits in multiple places throughout the body (kidney stones, vascular calcification, etc.). Calcifications appear on ultrasound as very bright masses or dots (Figure 1) with different shapes, and even more amazing is the uniform formation of calcifications around the tumor, showing eggshell-like changes (Figure 2), thus marveling at the creation of the gods of fate. Figure 1 Figure 2 Calcification plays an important role in the differentiation of benign and malignant breast or thyroid lesions. In the case of tumors, many studies have suggested that the coarser the calcification particles, the better the differentiation of the cancerous tissue and the less malignant it is. In fact, there are the following possible reasons for calcification in malignant tumors of thyroid or breast: 1) rapid growth of cancer cells and insufficient local blood supply to the cancer foci, resulting in necrosis and formation of calcified foci; 2) especially in breast cancer, cancer cells can secrete a large amount of calcium, resulting in calcium deposits. These calcifications are mostly microcalcifications, mostly less than 2 mm, and appear as pinpoint, granular, dotted, or sandy highlights under ultrasound (Figure 3, Figure 4). Microcalcifications are an important indicator for diagnosing thyroid cancer by ultrasound, and its correct diagnosis rate is about 83%-95%. Figure 3 Figure 4 Calcifications in benign thyroid or breast diseases may also have the following possible causes: 1) calcification of walls or compartments formed by inflammation, hematoma absorption and mechanization; 2) lesions of benign tumors (e.g. adenomas) often undergo collagen degeneration and vitreous changes due to dense fibrous tissue, or lead to calcification or ossification. These calcifications mostly appear as coarse calcifications, larger than 2 mm, and are ultrasonically manifested as bright masses, sheets, arcs, or other irregular forms (Figure 5). Figure 5 Therefore, when ultrasound suggests calcification, the patient needs to know first whether it is coarse or microcalcifications, otherwise it is not worth the cost to scare oneself to death. Of course, for those who suspect thyroid cancer due to microcalcifications, because the cancer itself is progressing slowly, they can calmly choose the time for surgery or puncture biopsy for further definite diagnosis; and once they suspect malignant tumor of breast, they can operate immediately as long as they are suitable for surgery, so that the tumor can be removed in time. Of course, ultrasound does not find calcification does not mean that there is no, for breast examination, mammography is also a very important means of examination, because it is more sensitive to calcification, but it uses the principle of X-rays, resulting in radiation damage, can not often do.