Non-invasive

In a pathology report, the term non-invasive means that a tumour or abnormal growth has not spread into the surrounding tissues. The abnormal cells are confined to the original layer of tissue where they started. This term is most often used to describe early-stage cancers or pre-cancerous conditions, but it also applies to all benign (non-cancerous) tumours, which by definition do not invade nearby tissues.

Some non-invasive tumours are composed of cells that appear cancerous under the microscope, but as long as those cells remain confined to the surface layer and have not invaded deeper tissue, the tumour is still considered non-invasive. For example, a diagnosis of carcinoma in situ means the tumour is cancerous but has not yet spread into nearby tissue.

Understanding whether a tumour is non-invasive is important because it helps doctors decide how likely it is to spread or cause harm, and what treatment may be needed.

Can non-invasive tumours spread to other parts of the body?

No. By definition, non-invasive tumours cannot spread to other parts of the body. The abnormal cells are confined to one area and have not gained the ability to invade or metastasize. However, in some cases, a non-invasive tumour can develop into an invasive tumour over time if not treated or monitored appropriately.

Can a malignant tumour be non-invasive?

Yes. A tumour can be made up of malignant (cancerous) cells but still be considered non-invasive if those cells have not yet spread into surrounding tissues. These tumours are often described as carcinoma in situ or intraepithelial carcinoma, depending on where they are found. If left untreated, some of these tumours may eventually become invasive and spread to other parts of the body.

What are some examples of non-invasive cancers?

Here are some common examples of non-invasive cancers and early-stage malignant tumours:

• Ductal carcinoma in situ (DCIS) – A non-invasive type of breast cancer where cancer cells are found inside the ducts but have not spread into the surrounding breast tissue.

• Lobular carcinoma in situ (LCIS) – A condition in the breast where abnormal cells are found in the lobules (milk-producing glands). While LCIS is not cancer, it is considered a marker for increased risk of developing invasive breast cancer.

• Adenocarcinoma in situ of the cervix – A non-invasive form of cervical cancer in which abnormal glandular cells are present only on the surface of the cervix.

• Urothelial carcinoma in situ of the bladder – An early-stage bladder cancer where abnormal cells are present on the inner lining of the bladder but have not invaded the muscle wall.

• Adenocarcinoma in situ of the lung – A non-invasive form of lung cancer where abnormal cells are found lining the small air sacs (alveoli) without invading deeper lung tissue.

• Melanoma in situ – An early stage of melanoma in which abnormal pigment-producing cells (melanocytes) are confined to the outermost layer of the skin (epidermis).

• Non-invasive papillary urothelial carcinoma – A bladder cancer in which tumour cells form finger-like projections (papillae) that are limited to the inner lining of the bladder. These tumours can be low grade or high grade. High grade tumours have a greater risk of becoming invasive over time.

• Squamous cell carcinoma in situ of the skin (Bowen disease) – A non-invasive skin cancer where abnormal squamous cells are found only in the epidermis and have not spread into deeper layers of skin.

Questions to ask your doctor

• Is my tumour non-invasive or invasive?

• What does that mean for my treatment plan?

• Is there a risk the tumour could become invasive in the future?

• How often will I need follow-up or monitoring?

• Are there treatment options to prevent progression?