What Is a Hypoechoic Mass?

Medical test results can be hard to understand. If an ultrasound finds a hypoechoic mass, you may have wondered what that means.

A hypoechoic mass looks dark gray on an ultrasound. That means the tissue is dense. It doesn’t always mean that something is wrong.

How Ultrasound Works

Ultrasound works by sending sound waves toward the object being tested. A machine records the sound waves. These are also called echoes. They bounce back and create an image that can be seen on a screen. The image is sometimes called a sonogram.

Diagnostic ultrasound uses sound wave technology to look at parts of your body, including:

  • Brain
  • Heart and blood vessels
  • Breast
  • Abdominal Organs
  • Eyes
  • Thyroid
  • Skin and muscles

Types of Ultrasound Images

Certain words are used to describe areas imaged with ultrasound. Masses can be hypoechoic, hyperechoic, anechoic, or mixed.

Hypoechoic. This term means "not many echoes." These areas appear dark gray because they don't send back a lot of sound waves. Solid masses of dense tissue are hypoechoic.

Hyperechoic. This term means "lots of echoes." These areas bounce back many sound waves. They appear as light gray on the ultrasound. Hyperechoic masses are not as dense as hypoechoic ones are. They may contain air, fat, or fluid.

Anechoic. This term means "without echoes." These areas appear black on ultrasound because they do not send back any sound waves. Anechoic masses are often fluid-filled.

Are Hypoechoic Masses Cancerous?

Ultrasounds are one tool in determining whether a mass is cancerous. Solid masses are hypoechoic and can be cancerous. Cysts filled with air or fluid are usually hyperechoic and are rarely cancerous. 

Abnormal tissue also looks different from healthy tissue on a sonogram. Your doctor will usually do further testing if an ultrasound shows a solid mass or what looks like abnormal tissue.

Ultrasounds help doctors identify benign or malignant tumors. Benign tumors are usually all one type of tissue. They typically have clearly defined borders. They don't invade other organs. But they may push on them or displace them.

Cancerous masses may contain more than one type of tissue. They often have irregular borders. They may invade nearby organs. It isn’t easy to tell the difference between benign and malignant masses. There can be an overlap between both types. 

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Other Conditions

Ultrasound results can mean different things depending upon which part of the body is being tested. Here are a few examples of hypoechoic masses that can happen in different areas.

Breast. Hypoechoic masses with irregular shapes in breast sonograms are suspicious. Some benign masses can be hypoechoic and may look like cancer. Ultrasound operators use special techniques to tell the difference between benign and malignant breast masses. Sometimes biopsies are necessary.

Thyroid. Many people have thyroid nodules (lumps). But only about 5% of thyroid nodules are cancerous. Ultrasound helps doctors find the ones that might be. Hypoechoic nodules that are 2 centimeters or more and contain calcium deposits are most likely to be cancerous.

‌Uterus. Fibroid tumors of the uterus are often found during ultrasound exams. They are benign but may be hypoechoic on a sonogram. Many women with fibroids have no symptoms. Fibroids are not cancerous, but they can cause severe symptoms.

WebMD Medical Reference

Sources

SOURCES:

ACTA INFORMATICA MEDICA: "Application of Ultrasound in Medicine."

Cancer Treatment Centers of America: "Ultrasound."

CLINICAL THYROIDOLOGY FOR THE PUBLIC: "THYROID NODULES."

INDIAN JOURNAL OF RADIOLOGY AND IMAGING: "Radiological appearances of uterine fibroids."

Korean Journal of Radiology: "Are Irregular Hypoechoic Breast Masses on Ultrasound Always Malignancies?: A Pictorial Essay."

National Institute of Biomedical Imaging and Bioengineering: "Ultrasound."

RadiologyInfo.org: "General Ultrasound."

Silkowski, C. Emergency Medicine Sonography: Pocket Guide to Sonographic Anatomy and Pathology, Jones and Bartlett, 2010.

SpringerLink: “Ultrasound of Soft Tissue Tumors.”

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