antagonist. 1. a muscle that counteracts the action of another muscle, its agonist. 2. a drug that binds to a cellular receptor for a hormone, neurotransmitter, or another drug blocking the action of that substance without producing any physiological effect itself.
in the body (Figure 20â1). In general, the more widely a cancer spreads, the harder it becomes to eradicate. It is generally metastases that kill the cancer patient. Cancers are traditionally classified according to the tissue and cell type from which they arise. Carcinomas are cancers arising from epithelial cells, and they
However, squamous cells also occur in the lining of the digestive tract, lungs, and other areas of the body, and SCC occurs as a form of cancer in diverse tissues, including the lips, mouth, esophagus, urinary bladder, prostate, lung, vagina, and cervix, among others. The tumor grows relatively slowly. 2  Unlike basal-cell carcinoma (BCC), squamous-cell carcinoma (SCC) has a substantial risk of metastasis. 3  Risk of metastasis is higher in SCC arising in scars, on the lower lips or mucosa, and occurring in immunosuppressed patients.