Squamous-cell carcinoma (SCC), also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the lining of the respiratory and digestive tracts.

The squamous-cell carcinomas of different body sites can show differences in their presented symptoms, natural history, prognosis, and response to treatment.

Human papillomavirus infection has been associated with SCCs of the oropharynx, lung, fingers, and anogenital region.

About 90% of cases of head and neck cancer (cancer of the mouth, nasal cavity, nasopharynx, throat and associated structures) are due to SCC.

Squamous-cell skin cancer is the second most common skin cancer, accounting for over 1 million cases in the United States each year.

Primary squamous-cell carcinoma of the thyroid shows an aggressive biological phenotype resulting in poor prognosis for patients.

Esophageal cancer may be due to either esophageal squamous-cell carcinoma (ESCC) or adenocarcinoma (EAC). SCCs tend to occur closer to the mouth, while adenocarcinomas occur closer to the stomach. Dysphagia (difficulty swallowing, solids worse than liquids) and painful swallowing are common initial symptoms. If the disease is localized, surgical removal of the affected esophagus may offer the possibility of a cure. If the disease has spread, chemotherapy and radiotherapy are commonly used.

When associated with the lung, it is typically a centrally located large-cell cancer (non-small-cell lung cancer). It often has a paraneoplastic syndrome causing ectopic production of parathyroid hormone-related protein, resulting in hypercalcemia, but paraneoplastic syndrome is more commonly associated with small-cell lung cancer. It is primarily due to smoking.