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Learning you have a desmoid tumor

An early and accurate diagnosis is important

Because desmoid tumors are not common and can look different in each person, they are not always diagnosed correctly right away. In fact, these tumors are wrongly diagnosed about 30% to 40% of the time.1

One common mistake is when doctors think it’s a lipoma (a harmless fatty lump).2 A desmoid tumor might also be mistaken for scar tissue or another kind of tumor.2,3

That can mean delays for some people in getting the care they need. But be encouraged that there are several ways to help get a timely and accurate diagnosis.

~30%

to

40%

of desmoid tumors are misdiagnosed1

The value of experience

Sarcoma specialists are desmoid tumor experts—doctors specifically trained in treating these rare soft tissue tumors.

A sarcoma specialist can help create a treatment plan for you.

Find a registry of sarcoma centers* on the website for Sarcoma Alliance for Research through Collaboration (SARC), a non-profit organization.

SpringWorks Therapeutics, Inc. is providing this link to help patients find a sarcoma specialist by region, but SpringWorks had no role in developing this registry and inclusion in this registry does not represent an endorsement or recommendation from SpringWorks for any center or physician.

“I would advise people to get a second or third opinion. This is your life. Go find the best care.”

Brad, a real person living with a desmoid tumor

There are several ways to help get a timely and accurate diagnosis

NCCN Guidelines for Patients® provides a roadmap to help patients understand their diagnosis and treatment options. The guidelines recommend a biopsy (where a small piece of the tumor is removed to be tested) of the desmoid tumor to confirm what it is. Imaging tests such as CT scan or MRI may also be needed for an accurate diagnosis.4

A misdiagnosis can result in delayed or incorrect treatment. This may lead to unnecessary surgery and risk of complications. Your doctor may choose to perform additional tests as well. If you have questions about getting diagnosed, be sure to ask your care team.

Evaluation and diagnosis

Medical history and physical exam

Imaging of the tumor, such as a CT scan or MRI4, can help doctors understand where the tumor is.7 A radiologist will review the images and write a report. They will send this report to your doctor, who will review these results with you4

Intra-abdominal desmoid tumor8
This scan shows the desmoid tumor, in the center indicated by a white arrow. The desmoid tumor is surrounding a large blood vessel (white arrowhead). The tumor’s multiple tendrils are extending and threatening the bowel.

Image adapted with permission from Braschi-Amirfarzan M, Keraliya AR, Krajewski KM, et al. Role of imaging in management of desmoid-type fibromatosis: a primer for radiologists. Radiographics. 2016;36(3):767-782. ©RSNA

Biopsy, or a tissue sample, is needed to diagnose a desmoid tumor. A biopsy is recommended before starting treatment.4,7 A pathologist will examine this tissue sample and write a report. They will send this report to your doctor, who will review these results with you

Additional tests that may be helpful:

  • To help diagnose desmoid tumors, doctors can perform a test called “staining” on the biopsy tissue. This involves adding a special dye to make it easier to see beta-catenin, which is a specific protein often present in these tumor cells7
  • Genetic testing may be recommended by your doctor to check for Familial Adenomatous Polyposis (FAP), a hereditary syndrome associated with desmoid tumors. A genetic counselor may then discuss the test results with you4

Beta catenin can play a key role in desmoid tumors…and be a clue to diagnosis 

Beta catenin is a protein found in cells throughout the body. One of the roles of beta catenin is to help regulate “cell signaling.”9 Cell signaling can instruct cells in the body when to grow and divide. Abnormal cell signaling may lead to tumor development and growth.10 Medical experts have found that beta catenin often accumulates excessively in desmoid tumors cells, causing tumors to overgrow.12

Beta catenin staining can help a pathologist determine whether a tumor is a desmoid tumor when they look at it under the microscope. Based on medical studies, 60% to 98% of desmoid tumors show beta catenin staining under a microscope.7

Knowledge is power

What questions should you ask your doctor? What are your options or next steps for desmoid tumor care? These are important aspects of making informed decisions for your health. These guides can help:

Doctor Discussion Guide

Download

Care Options Guide

Download

“When I meet someone who’s newly diagnosed, it’s important to know the resources available and to instill confidence in being able to advocate for themselves.”

Andrea, a real person living with a desmoid tumor

Lipoma is a common misdiagnosis for those with desmoid tumors2,† 

What are lipomas? 

Lipomas are abnormal, benign growths of fatty tissue. Like desmoid tumors, they can appear anywhere in the body.11, 12

Lipomas are the most common type of soft tissue tumor.11 They occur far more frequently than desmoid tumors.11 

  • 50% of soft-tissue tumors are lipomas13
  • 3% of soft-tissue tumors are desmoid tumors12

The rarity of desmoid tumors compared to lipomas may be one reason that desmoid tumors could be misdiagnosed as lipomas.1 For instance, among a sample of people whose desmoid tumors were initially misdiagnosed, 4 out of 10 tumors were mistaken for lipomas.2,†

From market research conducted by SpringWorks Therapeutics.2

Desmoid tumors and their “tendril-like” growths may be difficult to see fully using imaging tests like MRI, CT scans, or ultrasound.14 This may be another reason that a desmoid tumor could be misdiagnosed as a lipoma or another tumor type.  Under a microscope, the cells of a lipoma look very different than the cells of a desmoid tumor.7,11 A biopsy of the tumor is the only way to see these differences before surgery. Ask your doctor whether a biopsy is appropriate for you.

What are some important differences between lipomas and desmoid tumors? 

  • Age of patients affected: While desmoid tumors are diagnosed most frequently in younger adults (age 20-44), lipomas are more common in adults aged 40-6011,15
  • Considerations for surgery:  The infiltrative nature of desmoid tumors may make them challenging to remove surgically. Their “tendril-like” growths can extend into layers of tissue beyond the tumor itself.1 In contrast, lipomas are generally well-defined within a thin capsule of tissue.16 After surgery, lipomas generally do not recur (come back)11
  • Desmoid tumors, however, can come back after surgery. It is reported that desmoid tumors may come back 24% to 77% of the time.16,17 The risk of having desmoid tumors come back after surgery can be higher for younger patients and those with larger tumors. Tumor location is also important. Desmoid tumors in the extremities (arms, legs, hands, feet), chest wall, and within the abdominal cavity have a higher risk of coming back after being removed by surgery18

Questions to ask your doctor if you’ve been diagnosed with lipoma…and before treatment 

  • What kinds of tests (imaging, biopsy, genetic testing) have been used to confirm the diagnosis? Are there any other tests available for me?
  • Are there any other possible diagnoses? 
  • If your doctor is managing with a “watch and wait” approach, ask: When and how should the lipoma be monitored?
  • If you are considering surgery, ask: What are the possible benefits and risks of surgery? Will the tumor be tested by a pathologist after surgery?

If you have questions about the diagnosis or treatment, it may be worthwhile to consult with a sarcoma specialist. You can find a sarcoma center here.‡

Find a Sarcoma Center

SpringWorks Therapeutics, Inc. is providing this link to help patients find a sarcoma specialist by region, but SpringWorks had no role in developing this registry and inclusion in this registry does not represent an endorsement or a recommendation from SpringWorks for any center or physician.

Next: Care Options

  1. Kasper B, Baumgarten C, Garcia J, et al; Desmoid Working Group. An update on the management of sporadic desmoid-type fibromatosis: a European Consensus Initiative between Sarcoma PAtients EuroNet (SPAEN) and European Organization for Research and Treatment of Cancer (EORTC)/Soft Tissue and Bone Sarcoma Group (STBSG). Ann Oncol. 2017;28(10):2399-2408.
  2. Data on file. SpringWorks Therapeutics.
  3. Penel N, Coindre JM, Bonvalot S, et al. Management of desmoid tumors: a nationwide survey of labelled reference centre networks in France. Eur J Cancer. 2016;58:90-96.
  4. Referenced with permission from the NCCN Guidelines for Patients® for Soft Tissue Sarcoma, 2025. © National Comprehensive Cancer Network, Inc. 2025. All rights reserved. Accessed July 15, 2026. To view the most recent and complete version of the NCCN Guidelines for Patients, go online to NCCN.org/patientguidelines. NCCN makes no warranties of any kind whatsoever regarding their content, use, or application, and disclaims any responsibility for their application or use in any way.
  5. SARC (Sarcoma Alliance for Research through Collaboration). About SARC. Accessed June 24, 2024. https://sarctrials.org/about-sarc
  6. Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for Soft Tissue Sarcoma V.5.2026. © National Comprehensive Cancer Network, Inc. 2026. All rights reserved. Accessed July 27, 2026. To view the most recent and complete version of the guideline, go online to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way.
  7. Kasper B, Baldini EH, Bonvalot S, et al. Current Management of Desmoid Tumors: A Review. JAMA Oncol. Published online June 20, 2024. doi:10.1001/jamaoncol.2024.1805 https://jamanetwork.com/journals/jamaoncology/article-abstract/2820212
  8. Braschi-Amirfarzan M, Keraliya AR, Krajewski KM, et al. Role of imaging in management of desmoid-type fibromatosis: a primer for radiologists. Radiographics. 2016;36(3):767-782.
  9. Penel N, Chibon F, Salas S. Adult desmoid tumors: biology, management and ongoing trials. Curr Opin Oncol. 2017;29(4):268-274.
  10. NIH. National Cancer Institute. NCI dictionary of cancer terms: desmoid tumor. Accessed June 24, 2024. https://www.cancer.gov/publications/dictionaries/cancer-terms/expand/D
  11. Kolb L, Yarrarapu SNS, Ameer MA, et al. Lipoma. [Updated 2022 Jul 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507906/
  12. Constantinidou A, Scurr M, Judson I, Litchman C. Clinical presentation of desmoid tumors. In: Litchman C, ed. Desmoid Tumors. Springer; 2012:chap 2. Accessed June 24, 2024. https://www.researchgate.net/publication/226455135
  13. Li M, Zhang L, Xu XJ, Shi Z, Zhao XM. CT and MRI features of tumors and tumor-like lesions in the abdominal wall. Quant Imaging Med Surg. 2019;9(11):1820-1839.
  14. Rosa F, Marinetti C, Piscopo F, et al. Multimodality imaging features of desmoid tumor: a head-to-toe spectrum. Insights into Imaging. 2020;11(1):1-3.
  15. van Broekhoven DLM, Grünhagen DJ, den Bakker MA, van Dalen T, Verhoef C. Time trends in the incidence and treatment of extra-abdominal and abdominal aggressive fibromatosis: a population-based study. Ann Surg Oncol. 2015;22(9):2817-2823.
  16. Easter DW, Halasz NA. Recent trends in the management of desmoid tumors. Summary of 19 cases and review of the literature. Ann Surg. 1989;210(6):765-769.
  17. Skubitz KM. Biology and treatment of aggressive fibromatosis or desmoid tumor. Mayo Clin Proc. 2017;92(6):947-964.
  18. Crago AM, Denton B, Salas S, et al. A prognostic nomogram for prediction of recurrence in desmoid fibromatosis. Ann Surg. 2013;258(2):347-353.