An abnormal cell mass resulting from excessive multiplication of cells that varies in size, color, and shape is a:

The term that describes an abnormal cell mass resulting from excessive multiplication of cells, which exhibits variations in size, color, and shape, is a tumor. Tumors can be classified as benign or malignant, depending on their nature and potential to invade other tissues. They are characterized by uncontrolled cell division and can arise in any part of the body.

A neoplasm is a more general term that also refers to an abnormal proliferation of cells, which can include tumors but does not specify the characteristics such as size and shape variations implied in this question. A lesion typically refers to any abnormal tissue found on or in an organism, and while a tumor is a type of lesion, it does not encompass the specific characteristics mentioned. A cyst is a type of lesion but is specifically a sac-like structure in the body that contains fluid or semi-solid material, typically distinguishable from tumors by its encapsulated nature and generally uniform appearance.

Thus, the most fitting term for an abnormal mass with the described characteristics is a tumor, as it captures the essence of excessive cell multiplication and the variability in physical presentation.