Desmoid Tumor: Introduction

Approved by the Cancer.Net Editorial Board, 11/2022

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Desmoid Tumors. Use the menu to see other pages. Think of that menu as a roadmap for this entire guide.

What are tumors?

A tumor often begins when the DNA of healthy cells is damaged, causing the cells to change and grow out of control, forming a mass. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body, called metastasis, if it is not found early and treated. A benign tumor means the tumor can grow but will not spread to distant places in the body.

About desmoid tumors

Desmoid tumors are a type of soft-tissue tumor that come from fibrous tissue. They are related to connective tissue cancers called sarcomas, but desmoid tumors are not cancer because they do not spread to other parts of the body. Because fibrous tissue is found throughout the body, desmoid tumors can occur in many locations throughout the body.

Many desmoid tumors grow slowly and do not cause problems. But some desmoid tumors grow quickly and can interfere with the body's normal activities. Most desmoids are not life threatening. However, in rare cases, they can be life threatening when they are in very close contact with nearby vital tissues and organs, such as the kidneys, intestines, lungs, major blood vessels, or nerves. This type of tumor can be hard to remove and control, and they often recur, or come back, after surgery. Sometimes, desmoid tumors may shrink without any treatment and become inactive, more like a scar. If this happens, it is called spontaneous regression, and no further treatment is needed. (Learn more about treatment options later in this guide.)

Desmoid tumors begin in cells called fibroblasts, which are the most common type of cells in connective tissue. Fibroblasts also play an important role in wound healing. Desmoid tumors are sometimes referred to as aggressive fibromatosis, desmoid fibromatosis, or deep fibromatosis. They can occur in adults or children.

Although desmoid tumors can develop in many locations, they typically are found in an arm, a leg, or the abdomen. Doctors describe the tumors as:

  • Abdominal wall desmoid tumors. These tumors form within the abdominal wall, which surrounds the organs in the abdomen.

  • Intra-abdominal desmoid tumors. These tumors form in the mesentery, which is the tissue that provides blood vessels and padding to the intestines in the abdomen. They often cause no symptoms unless they compress internal organs or can be felt as a mass.

  • Extra-abdominal desmoid tumors. These tumors form in areas of the body other than the abdomen or abdominal wall. They typically are found in the shoulder, upper arms, chest wall, and upper legs. Sometimes they can be found in the head or neck. Rarely, they can be found in the urologic system, such as in the bladder or scrotum.

A person usually develops a single desmoid tumor, although it is possible to develop more than 1 at a time. When a tumor is found and the doctor believes it could be a desmoid tumor, it is very important to confirm the diagnosis by a biopsy so that appropriate next steps may be followed. Because desmoid tumors are very rare, it is best if an expert pathologist who is familiar with the disease examines the tissue sample. A pathologist is a doctor who uses a microscope to look at a specimen of the tumor to make the diagnosis.

The pathologist will look under the microscope to see the size and shape (called morphology) of the tumor cells and do special stains (called immunohistochemistry) to confirm or revise the diagnosis of desmoid tumor. Sometimes they need more information, and additional genetic tests are performed. If a desmoid tumor is diagnosed, it is important that you are cared for by a health care team that specializes in sarcoma.

Looking for More of an Introduction?

If you would like more of an introduction, explore these related items about sarcomas. Please note that these links will take you to other sections on Cancer.Net:

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with a desmoid tumor and general survival rates. Use the menu to choose a different section to read in this guide.