Fibrosarcoma · What It Is, Causes, Signs and Symptoms, Treatment, and More

Published: Jan 06, 2026

Author: Emily Miao, PharmD, MD•

Editor: Alyssa Haag, MD•

Editor: Lily Guo, MD•

Editor: Kelsey LaFayette, DNP, ARNP, FNP-

Illustrator: Abbey Richard, MSc

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What is a fibrosarcoma?

A fibrosarcoma is a rare type of neoplasm composed of fibroblasts (i.e., a mesenchymal cell that secretes collagen proteins in order to maintain the structural integrity of tissues) derived from connective fibrous tissues that wrap around the tendons, ligaments, and muscles. Fibrosarcomas can also occur in bones within the medullary canal (i.e., hollow part of the bone) or the periosteum (i.e., fibrous membrane covering the bone). Fibrosarcoma is a specific subtype of soft tissue sarcomas, which includes neoplasms of fat, blood vessels, nerves, and fibrous tissues. Depending on the subtype, size, and location of the fibrosarcoma, the cancer cells can spread to other areas of the body, including hematogenous (i.e., through the bloodstream) spread to soft tissues and bones.

Fibrosarcomas are classified as low- or high-grade based on their histology. Low- and high-grade fibrosarcomas exhibit a low and high degree of mitotic (i.e., cell dividing) activity, respectively. Additionally, there are two subtypes of fibrosarcoma, the infantile type (i.e., arises during infant years), which rarely metastasizes (i.e., when the primary tumor has spread to another part of the body); and the adult type (i.e., arising in older adults), which tends to metastasize to other areas of the body (e.g.,, lungs, other bones, lymph nodes, liver).

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What causes fibrosarcoma?

The exact cause of fibrosarcoma is currently unknown, but it is hypothesized that these tumors either arise from de novo genetic mutations (i.e., not inherited from parents) or germline mutations (i.e., mutation in germ cells passed onto offspring). Individuals who have received radiation therapy or high-intensity radiation to certain areas, like bone, are also at risk of developing fibrosarcoma in the long term. Additionally, existing scar tissue from burn injuries and foreign material (e.g., vascular grafts, joint prostheses) may increase the risk of fibrosarcoma formation.

What are the signs and symptoms of fibrosarcoma?

The most common sign of fibrosarcoma is a gradually enlarging, painless mass. Oftentimes the mass is firm, round, well-demarcated from the surrounding tissue, and is on average three to eight centimeters in size, however, these neoplasms can grow to larger sizes, especially if the location of the tumor originates in the thighs or retroperitoneum. As the tumor enlarges, symptoms may be associated with mass effect compression, which can include pain, paresthesias, and motor deficits (e.g. limping, difficulty using arms and legs) in the affected area. Rarely, individuals may experience nonspecific constitutional symptoms (i.e., fever, unintentional weight loss).

Finally, the infantile subtype typically presents with a rapidly growing mass at birth or shortly after, followed by slow growth; whereas the adult subtype is characterized by rapid growth, presenting typically between 20 to 60 years old.

How is fibrosarcoma diagnosed?

Diagnosis of fibrosarcoma begins with a thorough review of symptoms and medical history. A physical exam may identify suspicious soft tissue masses that are present and palpable lymph nodes, which suggest that the cancer has spread to other sites. Magnetic resonance imaging (MRI) is the preferred imaging modality to visualize the soft tissue mass and for staging purposes, to assess for other metastatic sites and/or lymph node involvement. Biopsy and/or surgical resection followed by histologic examination are also helpful in order to diagnose fibrosarcoma and will show typical immunohistochemistry characteristics. For example, vimentin may stain positive on immunohistochemistry as it is a marker indicative of mesenchymal cell origin (i.e., fibroblasts); desmin and smooth muscle actin will also stain positive, representing the myofibroblastic differentiation that is seen in fibrosarcoma.

How is fibrosarcoma treated?

Treatment for fibrosarcoma includes a variety of strategies including surgical resection, radiation therapy, and/or systemic therapy (e.g., chemotherapy or immunotherapy). Surgery is the mainstay of therapy for localized fibrosarcomas. In individuals who have undergone surgery with positive tumor margins (i.e., the presence of residual microscopic tumor despite resection), additional radiation therapy is used to eradicate these residual cancer cells. For fibrosarcomas that have metastasized to other body areas, systemic therapy including chemotherapy (e.g., doxorubicin) and/or immunotherapy (e.g., pembrolizumab) may be used. Individuals should be counseled on chemotherapy-related side effects including nausea, vomiting, diarrhea, and hair loss.

What are the most important facts to know about fibrosarcoma?

A fibrosarcoma is a rare type of neoplasm composed of fibroblasts that originate from connective fibrous tissues originating from tissues that wrap around the tendons, ligaments, and muscles. The exact cause of fibrosarcoma is unknown, but it is hypothesized that these tumors either arise from de novo genetic mutations (i.e., not inherited from parents) or germline mutations (i.e., mutation in germ cells passed onto offspring). Symptoms often include pain and paresthesias in the affected area due to compression by mass effect. Rarely, systemic constitutional symptoms like fever and weight loss may be present. The diagnosis is confirmed by radiographic imaging (i.e., MRI) and histopathology. Treatment options include surgical resection, radiation therapy, and systemic chemotherapy or immunotherapy.

Key Takeaways

Definition	A fibrosarcoma is a rare type of soft tissue sarcoma composed of fibroblasts derived from connective fibrous tissue that wrap around the tendons, ligaments, and muscles. Fibrosarcomas can also occur in bones within the medullary canal or periosteum.
Classification	Classification depending on mitotic activity: - Low-grade: low degree of mitotic activity - High-grade: high degree of mitotic activity Classification depending on age: - Infantile type (rarely metastasizes) - Adult type (tends to metastasize)
Causes	Exact cause unknown; hypothesis: - De novo genetic mutations - Germline mutations - Risk factors: - Radiation therapy or high-intensity radiation - Existing scar tissue from burn injuries and foreign material (e.g., vascular grafts, joint prostheses)
Signs and Symptoms	- Mass that is: - Gradually enlarging - Painless - Firm, round, and well-demarcated 3-8 cm in size (can grow larger, especially if located in thighs or retroperitoneum) - Larger tumor: mass effect compression - Pain, paresthesias, motor deficits - Nonspecific constitutional symptoms (fever, unintentional weight loss) - Infantile type: rapidly growing mass at birth or shortly after, followed by slow growth - Adult type: rapid growth, typically between 20 and 60 years old
Diagnosis	- Review of symptoms and medical history - Physical exam - MRI (staging, assessment for other metastatic sites/lymph node involvement) - Biopsy and/or surgical resection → histology - Immunohistochemistry for better characterization
Treatment	- Surgical resection - Mainstay of therapy for localized fibrosarcomas - Radiation therapy - If positive margins after resection - Systemic therapy (chemotherapy, immunotherapy) - If metastases present - Side effects: nausea, vomiting, diarrhea, weight loss

References

Augsburger D, Nelson PJ, Kalinski T, et al. Current diagnostics and treatment of fibrosarcoma -perspectives for future therapeutic targets and strategies. Oncotarget. 2017;8(61):104638-104653. Published 2017 Aug 10. doi:10.18632/oncotarget.20136

Coffin CM, Dehner LP. Soft tissue tumors in first year of life: a report of 190 cases. Pediatr Pathol. 1990;10(4):509-526. doi:10.3109/15513819009067140

ESMO/European Sarcoma Network Working Group. Soft tissue and visceral sarcomas: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up [published correction appears in Ann Oncol. 2015 Sep;26 Suppl 5:v174-7]. Ann Oncol. 2014;25 Suppl 3:iii102-iii112. doi:10.1093/annonc/mdu254

Folpe AL. Fibrosarcoma: a review and update. Histopathology. 2014;64(1):12-25. doi:10.1111/his.12282

World Health Organization Classification of Tumours Editorial Board. Soft Tissue and Bone Tumours, 5th ed, International Agency for Research on Cancer, 2020. Vol 3.