Glossary of terms

These definitions are simplified for everyday understanding. If you'd like a deeper explanation of any term in the context of your diagnosis, ask us in clinic — many of these words carry specific implications depending on the cancer involved.

"A word you can define is a word that has lost most of its power to frighten you. That is the entire point of this page."

A

Adenocarcinoma. A cancer that arises from gland-forming cells. Common in breast, lung, colon, prostate, pancreas, stomach. The word tells you the cell of origin, not the prognosis.

Adjuvant therapy. Treatment given after the main treatment (usually surgery) to reduce the chance of the cancer coming back. Adjuvant chemotherapy, adjuvant radiation, adjuvant hormone therapy.

Anaemia. Low haemoglobin in the blood. Causes fatigue, breathlessness on exertion, pale skin. Common during cancer treatment and usually manageable.

Antiemetic. A medicine that prevents or treats nausea and vomiting. Built into every modern chemotherapy regimen.

B

Benign. A growth or tumour that is not cancer. Benign tumours do not invade surrounding tissue or spread to distant organs. They may still need treatment if they cause pressure or other problems.

Biopsy. The removal of a small piece of tissue (or sometimes cells) to examine under a microscope. The diagnosis of cancer is almost always confirmed by biopsy.

Biomarker. A measurable substance — in blood, urine, or tissue — that tells us something about a cancer (presence, activity, treatment target, response to treatment). Examples: PSA in prostate cancer, HER2 in breast cancer.

Brachytherapy. A type of radiation therapy where the radiation source is placed directly inside or next to the tumour, rather than aimed from outside the body.

C

Carcinoma. A cancer that arises from the cells lining the surfaces of organs or glands. The most common category of cancer in adults. Includes adenocarcinoma, squamous cell carcinoma, transitional cell carcinoma, and others.

Chemotherapy. A family of medicines that target rapidly dividing cells — a feature of most cancers. Given by drip, by tablet, or sometimes by injection.

Clinical trial. A carefully designed research study testing a new treatment or a new use of an existing treatment in patients. All modern treatments came from clinical trials.

CT scan (computed tomography). A scan that uses X-rays to produce detailed cross-sectional images of the body. The workhorse of cancer staging.

Cycle. A repeating unit of chemotherapy — typically the treatment day(s) plus the rest period before the next treatment day. Often two or three weeks long.

Cytology. The microscopic examination of individual cells (rather than a tissue sample). Used in Pap smears, fluid samples, and some fine-needle aspirations.

D

Differentiation. How closely the cancer cells resemble the normal cells they came from. Well-differentiated cells look more normal and generally behave less aggressively; poorly differentiated cells look very abnormal and tend to be more aggressive.

DCIS (ductal carcinoma in situ). Early-stage breast cancer where abnormal cells are confined to the milk ducts. Highly treatable; not yet capable of spreading.

E

Echocardiogram. An ultrasound scan of the heart. Done before certain chemotherapy drugs (anthracyclines, trastuzumab) to check the heart's pumping function.

Endoscopy. Examination of the inside of the body using a thin flexible camera. Includes gastroscopy (stomach), colonoscopy (large bowel), bronchoscopy (airways), cystoscopy (bladder).

G

Grade. A measure of how abnormal cancer cells look under the microscope. Usually scored from 1 (well-differentiated, lower grade) to 3 or 4 (poorly differentiated, higher grade). Different from stage.

H

Histology. The microscopic examination of tissue. The histology report is your biopsy report.

Hormone therapy. Treatment that blocks or reduces the body's hormones to slow cancers driven by them. Used in many breast cancers (oestrogen blockers like tamoxifen, aromatase inhibitors) and in prostate cancer (androgen blockers).

I

Immunohistochemistry (IHC). Special stains applied to a biopsy that use antibodies to detect specific proteins on the cancer cells. IHC confirms the type of cancer and identifies treatment targets (HER2, ER, PR, PD-L1, and many others).

Immunotherapy. Treatment that activates the patient's own immune system to attack the cancer. Includes checkpoint inhibitors (pembrolizumab, nivolumab, atezolizumab), CAR-T cell therapy, and several other approaches.

In situ. "In place" — abnormal cells confined to the layer they started in, without invading surrounding tissue. Cannot spread to lymph nodes or distant organs while in situ.

Invasive. Cancer cells that have broken through the basement membrane into surrounding tissue. Once invasive, a cancer has the ability to spread.

L

Leukaemia. A cancer of the blood-forming cells in the bone marrow.

Lymph node. A small bean-shaped structure in the lymphatic system. Lymph nodes filter lymph fluid and are common sites of early cancer spread. Found throughout the body — neck, armpits, chest, abdomen, groin.

Lymphoedema. Swelling caused by impaired lymph drainage. A possible long-term effect of surgery or radiation that removed or affected lymph nodes — most commonly in an arm (after breast cancer surgery) or a leg.

Lymphoma. A cancer that arises from cells in the lymphatic system. Two main families: Hodgkin lymphoma and non-Hodgkin lymphoma. Most lymphomas are highly treatable.

M

Margin. The edge of normal tissue around a surgically removed tumour. A "clear" or "negative" margin means no cancer cells are seen at the edge; a "positive" margin means cancer cells reach the edge, suggesting some may have been left behind.

Metastasis (plural: metastases). Spread of cancer from where it started to another organ — liver, lung, bone, brain, distant lymph nodes. Also called "secondary" cancer, "M1 disease", or "Stage IV". The word describes location, not prognosis: metastatic cancers vary enormously in how they behave and how they respond to treatment.

MRI (magnetic resonance imaging). A scan that uses magnetic fields (no X-rays) to produce detailed images, especially of soft tissues — brain, spine, pelvis, liver, breast.

N

Neoadjuvant therapy. Treatment given before the main treatment (usually surgery) — for example, chemotherapy before surgery to shrink a tumour or radiation before surgery to a rectal cancer.

Neoplasm. A new, abnormal growth of tissue. May be benign or malignant. "Neoplasm" is a neutral term; it does not automatically mean cancer.

Neutropenia. A low neutrophil count — neutrophils are the white blood cells that fight bacterial infection. A common side effect of chemotherapy, increasing infection risk.

O

Oncologist. A doctor who specialises in cancer. Medical oncologists treat cancer with drugs (chemotherapy, immunotherapy, targeted therapy, hormone therapy). Surgical oncologists treat cancer with surgery. Radiation oncologists treat cancer with radiation. Most modern cancer care involves all three working together.

P

Palliative care. Care focused on relieving symptoms and improving quality of life — usually given alongside cancer-directed treatment, not instead of it. Palliative care is appropriate at any stage of illness, not just at the end of life.

Pathology. The medical specialty that diagnoses disease by examining tissue and cells. The pathology report is the foundation of any cancer diagnosis.

PET-CT. A scan that combines a PET (positron emission tomography) scan — which highlights metabolically active areas using a small amount of radioactive sugar — with a CT scan. Excellent for staging many cancers and detecting small areas of disease that other scans miss.

Port (port-a-cath). A small device implanted under the skin on the chest, connected to a large vein. Allows repeated chemotherapy delivery without damaging smaller veins. Usually placed in a short outpatient procedure.

Prognosis. The likely course and outcome of an illness, based on group statistics. A prognosis describes averages — many individuals do better, some do worse. It is a guide, not a verdict.

Protocol. A standardised treatment plan — the combination of drugs, doses, schedule and duration — that has been studied and shown to work for a particular cancer.

R

Radiation therapy (radiotherapy). Treatment that uses high-energy beams (usually X-rays) to damage cancer cells while sparing healthy tissue as much as possible. Given from outside the body (external beam) or sometimes from inside (brachytherapy).

Recurrence. The return of cancer after a period of being apparently cancer-free. Local recurrence means in the original area; distant recurrence means in another organ (metastasis).

Remission. A reduction or disappearance of the signs of cancer. Complete remission means no detectable cancer on examination, scans, and tests. Partial remission means a significant reduction. Remission can be temporary or long-lasting; some remissions become cures.

S

Sarcoma. A cancer that arises from connective tissues — bone, muscle, fat, blood vessels, cartilage. Much less common than carcinomas.

Staging. The process of determining how far a cancer has spread. Uses physical examination, biopsy, and imaging. Most solid cancers are staged from I (small, localised) to IV (distant spread), often using the TNM system.

T

Targeted therapy. Cancer treatment aimed at a specific molecular feature of the tumour — a protein, a gene mutation, a pathway. More precise than traditional chemotherapy and often better tolerated. Examples: trastuzumab for HER2-positive cancers, osimertinib for EGFR-mutated lung cancer, imatinib for CML and GIST.

TNM. The staging system used for most solid cancers. T = tumour size or extent; N = lymph node involvement; M = distant metastasis. Combined to give an overall stage from I to IV.

Tumour. An abnormal mass of tissue. May be benign or malignant. "Tumour" by itself does not mean cancer; "malignant tumour" does.

Tumour marker. A substance — usually a protein — produced by some cancers that can be measured in the blood. Used for monitoring response to treatment and detecting recurrence in specific cancers. Examples: CA 15-3 (breast), CA 19-9 (pancreas, biliary), CA 125 (ovary), CEA (colon), PSA (prostate), AFP (liver, testis), beta-hCG (testis, gestational tumours). Most are imperfect — they go up and down for reasons other than cancer too — so they are interpreted alongside other information, not in isolation.

U

Ultrasound. A scan that uses high-frequency sound waves to produce images. No radiation. Used for many purposes in cancer care — examining lymph nodes, the liver, breast lumps, the abdomen, and guiding biopsies.