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. Common types include: esophageal squamous-cell carcinoma: a type of esophageal cancer cutaneous squamous-cell carcinoma: a type of skin cancer squamous-cell carcinoma of the lung: a type of lung cancer squamous-cell carcinoma of the vagina: a type of vaginal cancer squamous-cell carcinoma of the thyroid: a type of thyroid cancer Despite sharing the name "squamous-cell carcinoma", the SCCs of different body sites can show differences in their presented symptoms, natural history, prognosis, and response to treatment. By body location Human papillomavirus infection has been associated with SCCs of the oropharynx, lung, fingers, and anogenital region. Head and neck cancer About 90% of cases of head and neck cancer (cancer of the mouth, nasal cavity, nasopharynx, throat and associated structures) are due to SCC. Skin Cutaneous squamous-cell carcinoma is the second most common skin cancer, accounting for over 1 million cases in the United States each year. Thyroid Primary squamous-cell carcinoma of the thyroid shows an aggressive biological phenotype resulting in poor prognosis for patients. Esophagus 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. Lung 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. Penis Human papillomavirus (HPV), primarily HPV 16 and 18, are strongly implicated in the development of SCC of the penis. Three carcinomas in situ are associated with SCCs of the penis: Bowen's disease presents as leukoplakia on the shaft. Around a third of cases progress to SCC. Erythroplasia of Queyrat, a variation of Bowen's disease, presents as erythroplakia on the glans. Bowenoid papulosis, which histologically