Certain high-risk features are markers of an aggressive squamous cell skin cancer. These features are related to the location, size, and pathologic features of the tumour as well as certain characteristics of the patient.


When the specialist examines your pathology specimen from the biopsy, s/he will evaluate if your cancer is advanced or not. If the tumour is not advanced and is still localized, a critical step is determining if the tumour has high-risk features suggesting it is aggressive. What’s aggressive behaviour for a squamous cell skin cancer? We can think of an aggressive skin cancer (like other cancers) as one that spreads to distant body sites. But squamous cell skin cancers can also act aggressively when they spread locally and invade other tissues such as your nerves, bone, and other structures. An estimated five percent of squamous cell skin cancers are aggressive, meaning they are at increased risk for causing a lot of damage when they grow deep below your skin, coming back to the same location, or spreading to other parts of your body.

Below are the features that make squamous cell skin cancer high risk. These can be related to the primary (original) tumour or the characteristics of the person who has the tumour .

High-Risk Features of the Primary Tumour

Large size: Size greater than 20 mm (2 cm or about 0.8 inch, the diameter of a pound). This designation applies to tumours on the trunk and extremities

Problematic location:

  • On sensitive/mucosal locations (such as the genitals) as well as areas that tend to have lots of sun exposure, such as the central face, eyelids, eyebrows, on or around the nose, lips, chin, jaw, temple, and ear (the mask area), hands, and feet
  • On an area without hair
  • On a site with previous skin damage. This could include a site that is inflamed, has an active wound, has a scar, or has been treated with radiation before. This is called a Marjolin ulcer

Specific Invasive Features:

  • Invading deeper than 6 mm (a little less than 1/4 inch) below the skin surface. This would extend beyond the fat pad that is below the skin surface (subcutaneous fat)
  • Invading bone, muscle, or cartilage
  • Growing into blood vessels or into nerves

Certain symptoms: Causing pain and itchiness (which may indicate neurologic involvement)

Certain tumor subtypes: Acantholytic, desmoplastic, and metaplastic

Presence of multiple tumours:

  • Poorly differentiated tumours. This detail about your tumour is something reported on your pathology report—it means has greater potential to cause trouble
  • A history of prior tumours coming back (recurrent tumours)

High-Risk Features of the Patient

Immunosuppression resulting from the immunosuppressive medications used after organ transplantation, infection with the human immunodeficiency virus (HIV), or certain blood cancers.

Older age with tumour(s) on the head and neck

A history of very intense/prolonged sun exposure

The greater number of high-risk features, the more likely the squamous cell skin cancer will have a poor outcome. To see how risk features are integrated into the staging of squamous cell skin cancer, see STAGING SQUAMOUS CELL SKIN CANCER: A PRACTICAL DESCRIPTION.

Examples of High-Risk Features

Below are images that illustrate some of the high-risk features described in the section High-Risk Features of The Primary Tumour.

This tumour’s large size (greater than 20 mm in diameter) makes it high risk.


A representation of the mask area. Tumours that arise in this area are high risk.


A high-risk squamous cell skin cancer on the ear (in the mask region).


A high-risk squamous cell skin cancer on the lower lip (in the mask region). Tumours are more common on the lower lip than the upper lip because of increased sun exposure.