Understanding Your Tumor Size

by Jane Ashley

The medical profession utilizes the metric system for measurement of tumor sizes. The system is internationally used and is the primary standard of measurement in the healthcare field. In the United States where we use inches, yards and miles along with ounces and pounds, we as patients are confused when our medical team tells us that our tumor is 5 cm in diameter.

Tumor Sizes In Centimeters

For some kinds of cancer, the size of the tumor determines the stage of the cancer. Staging for breast and lung cancer utilize the size of the tumor as part of the staging process. Even if the size of the tumor doesn’t determine the stage (colorectal or prostate), imaging reports report the size of tumors and lymph nodes in millimeters and centimeters.

How are measurements calculated in the metric system ?

You’ve probably noticed the kilometer markings on your car’s speedometer. Most over-the-counter medicines provide the dosage in milligrams; for example, aspirin come in 81 mg and 325 mg sizes. Yet liquid medications are sold here in the U.S. utilizing ounces and teaspoon measurements. However, wine is sold in 750 ml (milliliters) and 1.5 liter sizes.

It’s definitely confusing. People in the U.S. see both metric and the United States Customary System (USCS). We buy our meat in pounds and ounces and our wine in milliliters and liters.

However, all measurements within the U.S. medical system are metric. Because we are accustomed to a yard stick and a measuring tape that measure in inches, we are generally thrown for loop when we learn that we have a 4 cm tumor in our lung or breast. We don’t know if that’s large or small.

• Meter = 39.37 inches (just over a yard which is 36 inches). The meter is divided into 100 sections, called centimeters.
• Centimeter (cm) = 0.3937 inches, approximately 4/10th of an inch (a wee bit less than half of an inch), about the diameter of a Cheerio. The centimeter is divided into 10 sections, called millimeters.
• Millimeter (mm) = 0.03937 inches, approximately the diameter of the lead in a wooden pencil

What is a solid tumor and how is it measured?

There are two types of cancer – solid tumor cancers and blood cancers. The definition of a solid tumor, according to the National Cancer Institute, is “an abnormal mass of tissue that usually does not contain cysts or liquid areas. Solid tumors may be benign (not cancer), or malignant (cancer). Different types of solid tumors are named for the type of cells that form them. Examples of solid tumors are sarcomas, carcinomas, and lymphomas. Leukemias (cancers of the blood) generally do not form solid tumors.”


Common solid tumor cancers include:
• Anal
• Bladder
• Breast
• Cervical
• Colorectal
• Kidney
• Liver
• Lung
• Ovarian
• Pancreatic
• Prostate
• Thyroid

Sometimes, cancerous tumors are also called a nodule, growth, spot, met, lump or lesion. All of these terms are referring to a solid tumor. Solid tumors are visualized in CT scans, PET scans and MRIs. Radiologists measure their size in millimeters and centimeters and provide a measurement in 2 dimensions. For example, a radiologist may describe a tumor as being 3.0 cm x 2.7 cm. A lymph node may measure 1.2 cm x 1.0 cm. A small spot in our lung may be 8 mm x 11 mm.

Peach7 Centimeters

How big can cancerous tumors become?

Some tumors can become quite large. The size of the tumor helps determine the stage of some cancers, including breast, pancreatic, and lung. Part of the staging system describes the tumor, either the size or if the tumor has invaded nearby structures. Some tumors may grow as large as 5 cm, 10 cm or even larger.

The size of a tumor is often compared to the size of a pea (1 cm), peanut (2 cm), grape (3 cm), walnut (4 cm), lime (5 cm), egg (6 cm), peach (7 cm), or grapefruit (10 cm).

Treatments for solid tumors

The goal of treatment for solid tumor cancers is to remove the tumor or as much of the tumor as possible. Sometimes, a tumor grows around a nerve or blood vessel, making it impossible to remove the entire tumor without endangering the patient’s quality of life. A variety of methods, including a combination of two treatments, may be used on a solid tumor. 

Millimeter Sizes

Treatment options include:
• Surgery
• Radiation
• Immunotherapy
• Targeted therapy
• Hormone therapy
• Proton therapy
• Lasers
• Cryoablation (commonly known as freezing)
• Radiofrequency ablation
• Bone marrow transplant (for certain lymphomas)
• Clinical trials, testing new methods

Sometimes, chemotherapy, radiation or hormone therapy will be used before surgery to help shrink the tumor so that the surgery is easier and less invasive to perform. A combination of those may be used before surgery. Precision medicine, based on the patient’s biomarkers, may also be employed to shrink tumors.

Use this handy converter to convert centimeters to inches.

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