Cancer cell

Histology

When viewed under a microscope, cancer cells show distinct structural traits. Their nuclei tend to be oversized and irregularly shaped, with changes in form, size, protein makeup, and texture. Grooves, folds, or indentations may appear, chromatin can clump or spread out, and the nucleolus may swell. These nuclear abnormalities vary by cancer type and help in diagnosis and staging.

Causes

Cancer cells arise when the genes that control cell division get damaged. This damage, caused by mutations and epimutations in a cell's genetic material, throws off the normal balance between cell growth and cell death, leading to unchecked division. A single mutation isn't enough; a cell usually needs a series of mutations in specific gene classes to become cancerous.

DNA damage can come from radiation, chemicals, or other environmental factors, but mutations also build up naturally over time from uncorrected transcription errors, making age a risk factor. Some cancers are triggered by oncoviruses, and genetics also play a role. Research indicates that too much SP2 protein might turn stem cells into cancer cells, while a shortage of certain co-stimulated molecules can weaken natural killer cells, allowing cancer to develop.

DNA repair and mutation

If a cell cannot properly fix DNA damage, those errors build up. When the cell copies its DNA, these errors can cause mistakes, including mutations that may lead to cancer. Several inherited conditions that impair DNA repair raise cancer risk. For instance, many cancers show low levels of the repair enzyme O-6-methylguanine-DNA methyltransferase.

However, while a repair shortage can start a cancer, some cancer cells later boost their repair abilities. This can be important for treatment. For example, the DMC1 gene, normally active only in meiosis to protect germ cells, is also turned on in cervical, breast, and lymphoma cancers. Using such meiotic repair genes may help tumor cells handle their own internal DNA damage and can also make therapies like radiation less effective.

Discovery

Cancer's earliest known traces appear in Egyptian writings from 1538 BCE and in mummified bodies. In 2016, a team led by Edward John Odes reported a 1.7 million-year-old osteosarcoma, the oldest malignant hominin cancer ever found. During the Renaissance and Age of Discovery, understanding grew.

German biologist and politician Rudolf Virchow, a founder of cellular pathology, studied microscopic tissue and linked it to disease. In 1845, he and John Hughes Bennett separately spotted an abnormal rise in white blood cells; Virchow recognized it as a blood illness and named it leukämie in 1847. In 1857, he first described a chordoma tumor originating from the skull base.

Did You Know?

• Cells playing roles in the immune system, such as T-cells, use a dual receptor system when determining whether to kill sick or damaged human cells.
• Molecules including MIC-A and MIC-B are produced by cells under stress, turning into tumors, or infected, helping macrophages detect and kill cancer cells.
• In February 2019, medical scientists announced that iridium attached to albumin, creating a photosensitized molecule, can penetrate cancer cells and, after being irradiated with light, destroy them.