Tumor sizes are often measured in millimeters (mm) or centimeters. Common items that can be used to show tumor size in mm include: a sharp pencil point (1 mm), a new crayon point (2 mm), a pencil-top eraser (5 mm), a pea (10 mm), a peanut (20 mm), and a lime (50 mm).

A millimeter is the smallest unit of length marked on a metric ruler. A millimeter is one-tenth of a centimeter and it takes 2.54 cm to equal one inch.

Multiple myeloma is a cancer that forms in a type of white blood cell called a plasma cell. Healthy plasma cells help fight infections by making proteins called antibodies. Antibodies find and attack germs. In multiple myeloma, cancerous plasma cells build up in bone marrow.

A millimeter (abbreviated as mm and sometimes spelled as millimetre) is a small unit of Displacement (length/distance) in the metric system.