Benign vs malignant tumours: the comparison table !

Topic

Benign tumours stay put and look like their tissue; malignant ones invade, spread and look abnormal. Metastasis settles the question.

Updated 2026-11-01

What it is

The pathologist separates benign from malignant tumours with four criteria: differentiation, rate of growth, local invasion and metastasis. Only metastasis proves malignancy without doubt; invasion is the next most reliable sign. The distinction drives everything that follows: surgery margins, staging and prognosis.

Key facts

Some tumours sit in between: borderline tumours or tumours of low malignant potential (for example some ovarian epithelial tumours).
A capsule is a good sign but not proof: some malignant tumours grow with a pseudocapsule of compressed tissue.
Benign tumours of endocrine glands can secrete hormones and cause disease out of proportion to their size.

Benign or malignant: what to look for

Feature	Benign	Malignant
Differentiation	Well differentiated; resembles the tissue of origin	From well differentiated to anaplastic
Nuclei and mitoses	Uniform nuclei; few, normal mitoses	Pleomorphic, dark nuclei; many and atypical mitoses
Growth	Usually slow; may stop or regress	Usually faster and erratic; necrosis when it outgrows its blood supply
Border	Well demarcated, often with a fibrous capsule	Poorly demarcated; infiltrates and destroys
Local invasion	Absent	Present (crosses the basement membrane, nerves, vessels)
Metastasis	Never	Frequent; more likely with larger, less differentiated tumours
Recurrence after excision	Rare when fully removed	Common if margins are not clear

Clinical notes

Uterine fibroids (leiomyomas) are very common and benign; leiomyosarcoma usually arises on its own rather than from a fibroid.
Among benign liver masses, haemangioma is the most common; hepatocellular adenoma matters because it can bleed and, rarely, become malignant.
A colorectal adenoma is benign but is the precursor of most colorectal cancers, which is why polyps are removed at colonoscopy.
Fibroadenoma of the breast is a benign, mobile, well-circumscribed mass typical of young women.

Test yourself

Think of the answer, then tap the question to see it.

Which single feature proves that a tumour is malignant?

Metastasis: a deposit of the tumour at a site discontinuous with the primary.

Which malignant tumour invades locally but rarely metastasises?

Basal cell carcinoma of the skin (gliomas behave similarly inside the brain).

How can a benign tumour be lethal?

By its location (a meningioma compressing the brain, a cardiac myxoma blocking a valve) or by secreting hormones (pheochromocytoma, insulinoma).

Why is a fibrous capsule typical of benign tumours?

Slow, expansile growth compresses the surrounding stroma into a rim, so the tumour pushes tissue aside instead of infiltrating it.

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Elsewhere in DurgiPedia

Basement membrane

← All of general pathology

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: What Is Cancer? (National Cancer Institute (NCI), 2026); Tumor List | SEER Training (SEER Training Modules, National Cancer Institute, 2026); Tumor Grade (National Cancer Institute (NCI), 2026).

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Representative model, for educational purposes only.