nonmelanoma skin cancer
Meaning of nonmelanoma skin cancer: The commonest cancers in people with pale skin, grouped together by what they are not rather than by what they are.
Definition of nonmelanoma skin cancer
Nonmelanoma skin cancer is a collective label for every cancer that begins in the skin except melanoma. Basal cell carcinoma and squamous cell carcinoma account for almost all of it, both arising from keratinocytes, the cells that build the skin surface. The group also takes in several rare tumors of other skin cells. These cancers grow locally and reach distant organs far less often than melanoma.
What does the group include?
Two tumors dominate it so completely that the rest are footnotes. Basal cell carcinoma begins in the deepest layer of the epidermis and squamous cell carcinoma in the keratinocytes above it. Cancer registries usually count only these two, which is why many specialists now prefer the plainer name keratinocyte carcinoma. Rarer skin cancers exist, and whether they belong under the nonmelanoma heading depends on who is counting.
| Type | Where it starts | How it behaves |
|---|---|---|
| Basal cell carcinoma | Deepest layer of the epidermis | Grows slowly, spreads beyond the skin very rarely |
| Squamous cell carcinoma | Keratinocytes nearer the surface | Can reach lymph nodes, more so on lip or ear |
| Merkel cell carcinoma | Touch-sensing cells at the base of the epidermis | Rare and aggressive |
What drives it?
Cumulative ultraviolet exposure over a lifetime is the dominant influence, which is why these tumors cluster on the face, ears, scalp, neck, forearms and backs of the hands. Pale skin that burns rather than tans carries more risk, as does a long history of outdoor work or sunbed use. Radiation treatment to an area, arsenic exposure, chronic wounds and scars, and some inherited conditions all raise it. Long-term suppression of the immune system after an organ transplant raises it steeply, and squamous cell carcinoma rises disproportionately in that setting.
Why keep it separate from melanoma?
Because behavior differs sharply. Melanoma begins in the pigment-making cells and, left alone, spreads through the body while the visible lesion is still small. The tumors in this group stay put far longer and do their damage by eating into nearby tissue, which on a face means cartilage, bone or the eyelid. Sorted by number of cases, this group swamps every other form of skin cancer; sorted by deaths, melanoma dominates. That gap is the whole reason the two labels exist.
Also known as
Used in a sentence
The lesion was excised and reported as a nonmelanoma skin cancer.
Good to know
The label groups tumors by what they are not, so it spans very different behavior: basal cell carcinoma almost never spreads beyond the skin, while squamous cell carcinoma of the lip or ear can reach the lymph nodes.
Word origin
Where “nonmelanoma skin cancer” comes from
Melanoma joins Greek melas, black, to -oma, a swelling or tumor, so the negative label marks out the skin cancers that do not begin in the pigment-making cells.