Malignancy

Malignancy
Other names	Cancer, malignant neoplasm
Malignant tumor (right) spreads uncontrollably and invades the surrounding tissues; benign tumor (left) remains self-contained from neighbouring tissue
Specialty	Oncology
Symptoms	Fatigue, lump(s), change in skin, abnormal bleeding, prolonged cough, unexplained weight loss[1]
Risk factors	Smoking, sun exposure, genetics - history of malignancy, solid organ transplantation (post-transplant malignancy), infectious diseases
Diagnostic method	Biopsy
Treatment	Photoradiation therapy, surgery, chemotherapy, hyperthermia
Frequency	442.4 per 100,000 per year [2]
Deaths	~10 million per year [3]

Malignancy (from Latin male 'badly', and -gnus 'born') is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer.

A malignant tumor contrasts with a non-cancerous benign tumor in that a malignancy is not self-limited in its growth, is capable of invading into adjacent tissues, and may be capable of spreading to distant tissues.

A benign tumor has none of those properties, but may be harmful to health. The term benign in more general medical use characterises a condition or growth that is not cancerous, i.e. does not spread to other parts of the body or invade nearby tissue. Sometimes the term is used to suggest that a condition is not dangerous or serious.^[4]

Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis.^[5] Malignant tumors are also characterized by genome instability, so that cancers, as assessed by whole genome sequencing, frequently have between 10,000 and 100,000 mutations in their entire genomes.^[6] Cancers usually show tumour heterogeneity, containing multiple subclones.^[7] They also frequently have reduced expression of DNA repair enzymes due to epigenetic methylation of DNA repair genes or altered microRNAs that control DNA repair gene expression.

Tumours can be detected through the visualisation or sensation of a lump on the body.^[8] In cases where there is no obvious representation of a lump, a mammogram or an MRI test can be used to determine the presence of a tumour.^[8] In the case of an existing tumour, a biopsy would then be required to make a diagnosis and distinguish whether the tumour is malignant or benign.^[8] This involves examination of a small sample of the tissue in a laboratory.^[8] If detected as a malignant tumour, treatment is necessary; treatment during early stages is most effective.^[8] Forms of treatment include chemotherapy, surgery, photoradiation and hyperthermia, amongst various others.