{{further|List of oncology-related terms}}
The following closely related terms may be used to designate abnormal growths:
* '''Tumor or tumour:''' originally, it meant any abnormal swelling, lump or mass. In current English, however, the word tumor has become synonymous with neoplasm, specifically solid neoplasm. Note that some neoplasms, such as leukemia, do not form tumors.
* '''Neoplasm:''' the scientific term to describe an abnormal proliferation of genetically altered cells. Neoplasms can be benign or malignant:
** '''Malignant neoplasm''' or '''malignant tumor''': synonymous with '''cancer'''.
** '''Benign neoplasm''' or '''benign tumor''': a tumor (solid neoplasm) that stops growing by itself, does not invade other tissues and does not form metastases.
* '''Invasive''' tumor is another synonym of '''cancer'''. The name refers to invasion of surrounding tissues.
* '''Pre-malignancy''', '''pre-cancer''' or '''non-invasive''' tumor: A neoplasm that is not invasive but has the potential to progress to cancer (become invasive) if left untreated. These lesions are, in order of increasing potential for cancer, atypia, dysplasia and carcinoma in situ.
The following terms can be used to describe a cancer:
* '''Screening''': a test done on healthy people to detect tumors before they become apparent. A mammogram is a screening test.
* '''Diagnosis''': the confirmation of the cancerous nature of a lump. This usually requires a biopsy or removal of the tumor by surgery, followed by examination by a pathologist.
* '''Surgical excision''': the removal of a tumor by a surgeon.
** '''Surgical margins''': the evaluation by a pathologist of the edges of the tissue removed by the surgeon to determine if the tumor was removed completely ("negative margins") or if tumor was left behind ("positive margins").
* '''Grade''': a number (usually on a scale of 3) established by a pathologist to describe the degree of resemblance of the tumor to the surrounding benign tissue.
* '''Stage''': a number (usually on a scale of 4) established by the oncologist to describe the degree of invasion of the body by the tumor.
* '''Recurrence''': new tumors that appear at the site of the original tumor after surgery.
* '''Metastasis''': new tumors that appear far from the original tumor.
* '''Transformation:''' the concept that a low-grade tumor transforms to a high-grade tumor over time. Example: Richter's transformation.
* '''Chemotherapy''': treatment with drugs.
* '''Radiation therapy''': treatment with radiations.
* '''Adjuvant''' therapy: treatment, either chemotherapy or radiation therapy, given after surgery to kill the remaining cancer cells.
* '''Prognosis''': the probability of cure after the therapy. It is usually expressed as a probability of survival five years after diagnosis. Alternatively, it can be expressed as the number of years when 50% of the patients are still alive. Both numbers are derived from statistics accumulated with hundreds of similar patients to give a Kaplan-Meier curve.