Congenital Fibrosarcoma

• Congenital fibrosarcoma is a rare soft tissue cancer affecting newborns.
• It often presents as a rapidly growing mass, most commonly on limbs.
• Diagnosis involves imaging, biopsy, and genetic testing for specific translocations.
• Treatment primarily involves surgical removal, sometimes followed by chemotherapy or targeted therapy.
• Prognosis is generally favorable with complete surgical resection, though recurrence is possible.

What is Congenital Fibrosarcoma?

What is Congenital Fibrosarcoma? It is a rare mesenchymal tumor, meaning it originates from connective tissues, and is present at birth or manifests within the first few months of life. This aggressive yet often curable cancer accounts for less than 1% of all childhood soft tissue sarcomas, making it an uncommon diagnosis in pediatric oncology. Unlike adult fibrosarcoma, the congenital form often has a more favorable prognosis, particularly when completely resected.

Causes of Congenital Fibrosarcoma

The exact causes of congenital fibrosarcoma are not fully understood, but genetic factors play a significant role. A hallmark genetic abnormality associated with this tumor is a specific chromosomal translocation, most commonly t(12;15)(p13;q25), which results in the ETV6-NTRK3 gene fusion. This fusion gene leads to uncontrolled cell growth and proliferation, driving tumor development. While this genetic alteration is a key driver, it is not inherited, meaning it arises spontaneously during fetal development rather than being passed down through families. Environmental factors are not typically implicated in its etiology.

Symptoms and Early Diagnosis

Recognizing the signs of congenital fibrosarcoma early is crucial for effective management. While it is rare, prompt identification of congenital fibrosarcoma symptoms can significantly improve outcomes.

Key Symptoms to Look For

The most common symptom is the presence of a rapidly growing, firm, and often painless mass. This mass can vary in size and is most frequently found on the extremities (arms or legs), but can also appear on the trunk, head, or neck. Key symptoms include:

• Palpable Mass: A noticeable lump or swelling, often firm to the touch, most commonly on the extremities.
• Rapid Growth: The mass typically increases in size quickly, which can be alarming to parents.
• Skin Changes: The overlying skin might appear discolored (reddish or bluish) or stretched, sometimes with visible superficial veins.
• Functional Impairment: Depending on the tumor’s location, it might restrict movement of a limb or cause pressure on surrounding structures.

Diagnostic Methods

Diagnosis typically begins with a physical examination and imaging studies. A definitive diagnosis requires a biopsy, where a tissue sample is taken from the tumor and examined under a microscope by a pathologist. Diagnostic methods include:

• Physical Examination: Initial assessment by a clinician to identify the mass.
• Imaging Studies:
  • Ultrasound: Often the first imaging technique to evaluate the mass.
  • MRI (Magnetic Resonance Imaging): Provides detailed images to define tumor size, extent, and relationship to surrounding tissues.
• Biopsy: A definitive diagnosis requires a tissue sample from the tumor for histopathological analysis.
• Genetic Testing: Performed on biopsy samples to identify characteristic gene fusions, such as ETV6-NTRK3, which confirms the diagnosis and guides treatment.

Treatment and Prognosis

Effective management of congenital fibrosarcoma relies on a multidisciplinary approach, with treatment strategies tailored to the individual patient’s condition. Understanding congenital fibrosarcoma treatment options is vital for families.

Current Treatment Approaches

The primary treatment for congenital fibrosarcoma is surgical resection, aiming for complete removal of the tumor with clear margins. Due to the tumor’s often infiltrative nature and proximity to vital structures, achieving clear margins can be challenging.

In cases where complete surgical removal is not feasible or if there is a high risk of recurrence, chemotherapy may be used. Chemotherapy can help shrink the tumor before surgery (neoadjuvant chemotherapy) or eliminate any remaining cancer cells after surgery (adjuvant chemotherapy). Targeted therapies, specifically NTRK inhibitors, have shown promise in cases with the ETV6-NTRK3 fusion, offering a less toxic alternative or addition to traditional chemotherapy, especially for unresectable or recurrent tumors. Radiation therapy is generally avoided in infants due to potential long-term side effects but might be considered in very specific, challenging cases.

Long-Term Outlook

The prognosis for infants with congenital fibrosarcoma is generally favorable, especially when complete surgical resection is achieved. The overall survival rate is high, often exceeding 80-90% with appropriate treatment. However, local recurrence can occur, necessitating close follow-up and potential further interventions. Regular monitoring with imaging studies is essential to detect any recurrence early. Long-term follow-up is crucial to manage any potential late effects of treatment and to ensure the child’s overall health and development.