squamous cell carcinoma
Meaning of squamous cell carcinoma: One name across many organs, united by the flat lining cell the cancer starts from rather than by where it is found.
Definition of squamous cell carcinoma
Squamous cell carcinoma is a cancer arising from squamous cells, the flat, tile like cells that form the outer layer of the skin and line the mouth, throat, esophagus, airways, cervix and anus. Because those cells occur in so many places, the name identifies a cell of origin rather than one organ or one disease.
Where does it arise, and what drives it?
The common thread is long term injury to a squamous surface, though the injuring agent differs by site.
| Site | Main contributors |
|---|---|
| Skin | Cumulative ultraviolet exposure; also long term immune suppression, previous radiation, arsenic, and scars or ulcers present for years |
| Lip and mouth | Tobacco in any form, alcohol, betel quid, and sun exposure for the lower lip |
| Throat | Persistent high-risk human papillomavirus infection, tobacco and alcohol |
| Esophagus | Tobacco, alcohol and very hot drinks |
| Lung | Smoking, with tumors typically arising in the larger central airways |
| Cervix and anus | Persistent high-risk human papillomavirus infection |
On the skin it usually appears as a scaly, crusted patch, a firm raised nodule, or a sore that does not heal, most often on the face, ears, scalp, lips and backs of the hands. Elsewhere it is noticed by what it obstructs or irritates: hoarseness, difficulty swallowing, bleeding or a persistent cough.
What comes before it?
Squamous cancers rarely appear without warning. On sun exposed skin they are preceded by rough scaly patches called actinic keratoses, and by a stage confined entirely to the surface layer. On mucous membranes the equivalent stage is a squamous intraepithelial lesion, in which the cells look abnormal but have not crossed the thin boundary beneath the surface. Crossing that boundary is what makes any carcinoma invasive, and it is the point at which spread becomes possible.
How does it differ from basal cell carcinoma?
Both are common skin cancers driven by ultraviolet damage, and they start from different layers of the epidermis. Basal cell carcinoma is the more frequent and grows locally, sometimes destructively, but almost never spreads to distant sites. Squamous cell carcinoma of the skin can spread, usually first to nearby lymph nodes, though the great majority of small, superficial tumors never do. Size, depth, location, growth pattern under the microscope and the state of the immune system are what separate the low risk majority from the minority that behave aggressively.
Also known as
Used in a sentence
The biopsy of the lesion confirmed squamous cell carcinoma with clear margins.
Good to know
Squamous cell carcinoma of the skin carries a higher risk of spreading than basal cell carcinoma, which is one reason the two are evaluated and followed differently despite both being common skin cancers.
Word origin
Where “squamous cell carcinoma” comes from
Formed from squamous, from Latin squama, meaning scale, and carcinoma, from Greek karkinoma, itself from karkinos, meaning crab, and -oma, meaning tumor.