Calcium is a mineral found throughout the body. Cells need calcium to function normally. Calcification is a word pathologists use when calcium builds up inside of a tissue sample. When examined under a microscope areas of calcification look much darker than the surrounding normal tissue.
Calcifications can be seen on routine H&E stained slides. Pathologists can also perform a special stain called a von Kossa stain to see calcium inside a tissue sample.
Normal calcium in the body
Most of the calcium in our body is found in our bones where it is used to make the bones strong. Small amounts of calcium are also found inside cells throughout our body and in our blood. It is normal to see calcification when looking at bones under the microscope. It is not normal to see calcifications in other types of tissues.
What causes calcification?
There are many reasons for finding calcifications inside of a tissue sample. The cause depends on the type of tissue involved and your medical history. Other changes seen around the area of calcification can also help determine the cause. Tissues that die may calcify especially in young people. Older people may also get calcium in some of their tissues as they get older.
The most common causes for calcifications are:
- Injury or infection – Any tissue that is damaged by an injury or infection can develop calcifications. Calcifications can also be caused by a previous medical procedure such as a biopsy. Sometimes the calcifications are so large that they can be felt when the tissue is touched. The calcifications are caused by calcium released from the damaged cells.
- Tumours – Some tumours can cause calcifications as the cells in the tumour die and release their calcium into the surrounding tissue. Calcifications can be seen in both non-cancerous (benign) and cancerous (malignant) tumours. Calcifications are very commonly seen in tumours of the breast. Pathologists sometimes describe calcifications seen with a tumour as dystrophic calcification.
- Chronic inflammation – Chronic inflammation is a term pathologists use to describe a type of immune response that lasts for a long time (usually weeks, months, or even years). Over time, chronic inflammation can damage the surrounding tissue and cause calcifications to develop. Calcifications caused by chronic inflammation are commonly seen in blood vessels, especially in people older than 50 years of age.
- Increased calcium in the blood – Increased calcium in the blood is called hypercalcemia. If hypercalcemia is severe (very high) or continues for a long period of time, some of the calcium can leave the blood and enter the surrounding tissue. In this situation calcifications can be seen in the walls of the blood vessels or the tissue surrounding the blood vessels.
Microcalcification is a word pathologists use to describe very small calcifications. Microcalcifications can be seen any where in the body although this description is most commonly used to describe small calcifications in the breast. Radiologists also use the word microcalcifications to describe small calcifications seen on radiological images.
A psammoma body is a term pathologists use to describe a special type of calcification. A psammoma body is different from other types of calcifications because it is round and is made up of many layers. When examined under the microscope, a psammoma body looks like the inside of a sliced onion.