a malignant new growth made up of epithelial cells tending to infiltrate surrounding tissues and to give rise to metastases. A form of cancer, carcinoma makes up the majority of the cases of malignancy of the breast, uterus, intestinal tract, skin, and tongue. malignant new growth made up of epithelial cells tending to infiltrate surrounding tissues and to give rise to metastases. A form of cancer, carcinoma makes up the majority of the cases of malignancy of the mammary gland, uterus, intestinal tract, skin and tongue.