malignancy
Meaning of malignancy: Where a cancer began, not where it is found, is what names it, and the tissue of origin sets everything that follows.
Definition of malignancy
Malignancy is a disease process in which abnormal cells divide without the usual restraints and can invade nearby tissue or travel through blood or lymph to grow at distant sites. The word is used both for that capacity and as a name for a cancer itself, and it is what separates cancer from a benign growth.
How are malignancies classified?
The first question asked of any cancer is which kind of cell it came from, because that determines almost everything else about it.
| Category | Tissue of origin | Examples |
|---|---|---|
| Carcinoma | Cells lining or covering surfaces and glands | Breast, lung, colon, prostate and skin cancers; the large majority of all cancers |
| Sarcoma | Connective tissue: bone, cartilage, muscle, fat, blood vessels | Osteosarcoma, liposarcoma, soft tissue sarcoma |
| Leukemia | Blood forming tissue in the bone marrow | Acute and chronic leukemias, which circulate rather than forming a lump |
| Lymphoma and myeloma | Cells of the immune system | Hodgkin and non-Hodgkin lymphoma, multiple myeloma |
| Central nervous system tumors | Brain and spinal cord tissue | Glioma, medulloblastoma |
| Melanoma and germ cell tumors | Pigment cells, and the cells that give rise to eggs and sperm | Melanoma, testicular and ovarian germ cell tumors |
Why does origin matter more than location?
A cancer keeps the identity of the tissue it started in wherever it ends up. Breast cancer that has spread to bone is still breast cancer, made of breast cells, and it is treated as breast cancer rather than as a bone tumor. That distinction between a primary cancer and a deposit from elsewhere is one of the first things established, since the two behave and respond entirely differently. Where the primary cannot be identified, the case is described as cancer of unknown primary and worked up specifically to find it.
How is it confirmed?
Tissue is the standard. A sample is examined for the features that define a malignant process: invasion beyond the normal boundary, disordered architecture, abnormal nuclei and frequent division. Stains that detect particular proteins identify the cell lineage when appearance alone is not enough, and molecular testing increasingly names the specific genetic changes driving the tumor. For cancers arising in the marrow, sampling the marrow itself takes the place of a solid tissue biopsy. Where the findings fall short of invasion, the process may be labeled benign or as a precursor change rather than a malignancy.
Used in a sentence
The biopsy findings were consistent with malignancy, prompting referral to oncology for further evaluation.
Good to know
Malignancy is defined by its capacity to invade surrounding tissue and spread to distant sites, which distinguishes it from a benign growth that may still enlarge locally but does not spread elsewhere in the body.
Word origin
Where “malignancy” comes from
From Latin malignus, meaning ill natured or harmful.