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NCI Dictionary of Cancer Terms


carcinoma in situ  listen  (KAR-sih-NOH-muh in SY-too)

  A group of abnormal cells that remain in the place where they first formed. They have not spread. These abnormal cells may become cancer and spread into nearby normal tissue. Also called stage 0 disease.

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Two-panel drawing showing layers of tissue, including the outer tissue layer, muscle layers, connective tissue, and inner tissue layer. The left panel shows carcinoma in situ (abnormal cells) in the inner tissue layer. The right panel shows cancer cells spreading from the inner tissue layer to the connective tissue and muscle layers.