An abnormal mass varying in size, shape, and color is termed a:

The correct choice is "tumor," as a tumor specifically refers to an abnormal mass of tissue that results from excessive cell growth. Tumors can be benign (non-cancerous) or malignant (cancerous), and they vary in size, shape, and color. This definition aligns well with the descriptors provided in the question, emphasizing the abnormality in the growth or mass.

Other terms, such as "lesion," generally refer to any damaged or abnormal area of tissue, which might not always be a mass or growth. Similarly, "growth" is a broader term that could refer to any kind of increase in tissue, not necessarily abnormal. "Wart" specifically refers to a small, benign growth caused by a viral infection and does not encompass the wider variety of conditions implied by the term "tumor." Therefore, "tumor" is the most accurate term that fits the description given in the question.