A 3-month-old child with a large left leg tumefaction.
A 3-month-old child was brought to our department with a large left leg tumefaction. A Magnetic Resonance examination (MR) was performed, showing a dishomogeneous huge mass (70mm) with liquid and necrotic areas in both spin echo T1-weighted and T2-weighted (Fig. 1). Incisional biopsy and histological study of the lesion were performed and congenital fibrosarcoma diagnosis was done. A similar smaller mass appeared at the posterior aspect of the right hemithorax within the following weeks.
Chemotherapy with Vincristine and Actinomicina-D was initiated. Chest and abdominal Computer Tomography (CT) was performed for staging. It showed additional lesions at right trapezius muscle and at the right piriformis muscle (Fig. 2). A MR examination was performed, confirming the presence of all these lesions with necrotic and liquid characteristics (Fig. 3).
Subsequently, a new MR study was performed to evaluate chemotherapy response of the disease. It showed a significant decrease of the mass lesions at the trapezius and piriformis muscles and of the of leg lesion (Fig. 4). Surgical treatment is planned after further chemotherapy.
Fibrosarcoma accounts for 9,5% of congenital neoplasias and for 3% of childhood tumours. It is called “congenital” because it is present at birth in approximately 37% of the cases, as a swelling or a mass that usually affects the distal portion of the extremities. Location at the trunk, head and neck regions is also possible. Usually, the mass becomes evident during the first year of life.
Congenital fibrosarcoma is considered a separate entity to its adult counterpart because of its clinical course is more favorable and metastatic spread is rare. Furthermore, congenital forms are associated the chromosomal translocation t(12;15); (p13;q25) with ETV6-NTRK3 gene fusion.
Differential diagnosis includes rhabdomyosarcoma, vascular tumours and infantile myofibromatosis. Histological analysis is mandatory, because clinical and imaging aspects are non-specific.
The most common radiological finding is a fast growing mass in the soft tissues. Radiographs can show bone incurvation, cortical swelling and rarely destruction of adjacent bones. Ultrasound (US) evaluation is useful in assessing the cystic,solid or vascular nature of the lesions. Computer Tomography (CT) examination may assess tumor size and bone involvement. On MRI, spin echo T1-weighted images before and after gadolinium and T2-weighted images are sufficient to characterize the lesions; fat suppression images add additional information if the tumour displays heterogeneous components. Scintigraphy with 99mTc-metilendifosfonato may show activity of adjacent bones and the presence of bone metastases.
Despite rapid growth and a high degree of cellularity, treatment with wide local excision without additional radiation- or chemotherapy is usually successful in most cases. In some cases amputation is necessary if the extent or large size of the tumour precludes surgical therapy. Chemotherapy is used in non operable tumours and as neoadjuvant therapy is useful for decreasing tumour bulk. Evidences suggest that the ETV6-NTRK3 gene fusion may underlie the distinctive biological properties of these tumours and may also indicate tumour chemosensitivity.
Congenital fibrosarcoma has a relatively good prognosis and only rarely metastasises. Prognosis is better if the chromosomal translocation is found. Recurrence rate is 17-40% with a five years survival of 84-93%. Metastasis rate depends on the site of the primitive tumour: 8% for location at the limbs , 26% for axial location. One case of spontaneous regression of neonatal fibrosarcoma is described in literature.
Multisegmental neonatal fibrosarcoma.
1. In this set of MRI and CT images, a relatively large soft tissue mass is seen in the left lower limb (from the thigh to the lower leg), appearing multilobulated and occupying most of the intermuscular spaces.
2. On MRI, the lesion generally shows an isointense or slightly hypointense signal on T1-weighted images and a relatively high mixed signal on T2-weighted images. Multiple hyperintense areas are observed, suggesting possible cystic or necrotic components. After contrast enhancement, varying degrees of enhancement may be noted.
3. The boundary between the lesion and the surrounding muscles and subcutaneous tissue is partially clear, with local compression or displacement of muscle groups. However, there is no obvious sign of bone destruction at present.
4. On CT scans (plain), a soft tissue density lesion is visible with relatively clear margins; no significant cortical bone destruction is noted, but local areas may show pressure-related changes.
Based on the patient’s age (3 months), clinical presentation (a congenital or rapidly enlarging soft tissue mass appearing shortly after birth), and the imaging features of a large, multilobulated soft tissue mass, the following considerations should be taken into account:
1. Congenital Fibrosarcoma: Commonly identified at birth or within the first year of life, often affecting the distal extremities. The mass can grow rapidly, but the overall malignant potential is relatively low. Imaging typically shows a solid soft tissue lesion which may have cystic or necrotic areas.
2. Rhabdomyosarcoma: One of the most common types of soft tissue sarcoma in children. It usually exhibits rapid growth and appears as a soft tissue mass on MRI with high T2 signal. Its histological features differ from congenital fibrosarcoma, requiring histopathological evaluation for definitive diagnosis.
3. Vascular Tumors (e.g., Infantile Hemangioma): Also common in infants. They can enlarge with the child’s growth, but imaging would typically reveal distinct vascular pathways or flow voids, with complex enhancement in multiphase scans, which may differ from the presentation in this case.
4. Infantile Myofibromatosis: May present as single or multiple nodules involving subcutaneous tissue and muscle, sometimes extending to bone. However, lesions are often smaller and more scattered compared to congenital fibrosarcoma, thus needing differentiation.
Taking into account:
- The patient’s age (3 months) and disease onset (congenital or noticed shortly after birth);
- Imaging findings suggesting a large, multilobulated soft tissue mass with a high T2 signal, as well as cystic or necrotic components, and no definite widespread bone destruction;
- Literature reports on congenital fibrosarcoma in this age group (rapid growth but relatively low malignancy, commonly affecting distal extremities);
The most likely diagnosis is Congenital Fibrosarcoma. While imaging findings are highly suggestive, histopathological biopsy is necessary for confirmation.
1. Treatment Strategy:
• Surgical Treatment: If pathological examination confirms congenital fibrosarcoma, the first choice is wide local excision. Because its biological behavior is relatively low-grade, complete resection often results in a favorable prognosis.
• Limb/Function Preservation: Maintain limb function whenever possible. If the tumor is too large or cannot be completely removed surgically, neoadjuvant chemotherapy can be considered to shrink the tumor before surgery. If the lesion is too extensive, amputation may still be necessary.
• Chemotherapy: For unresectable or recurrent lesions, neoadjuvant or adjuvant chemotherapy can be used. In particular, the presence of the ETV6-NTRK3 gene fusion often indicates better chemotherapy sensitivity.
• Radiotherapy: Given the young age and disease characteristics, radiation therapy is not generally a first-line option for congenital fibrosarcoma. It may be considered if the tumor cannot be completely resected and is resistant to chemotherapy, or if there is a high risk of local recurrence.
2. Rehabilitation and Exercise Prescription:
• Short-Term Rehabilitation (preoperative or early postoperative): The focus is on maintaining basic limb function and preventing joint contractures. Gentle passive or active range-of-motion exercises may be done, avoiding vigorous activities or pulling on the incision site. If immobilization or casting is needed postoperatively, activities should be gradually increased under professional guidance.
• Mid-Term Rehabilitation (after wound healing): Gradually increase muscle strength training and range of motion. Exercise intensity should progress from low to moderate, performed daily or every other day, in a stepwise manner. For instance, if limb function allows, add resistance exercises (such as light elastic band or bodyweight exercises), 10-15 minutes each session, 3-5 times a week.
• Long-Term Rehabilitation (functional reconstruction phase): Once tumor recurrence is ruled out, gradually resume moderate-intensity exercises to promote bone and muscle development. As the child grows, each session can be extended to 20-30 minutes, 3-5 times a week, adjusting weights and exercise methods according to the recommendations of the attending physician or physical therapist.
• Precautions: Because of the patient’s young age, special attention should be paid to the limb’s blood supply, nerve function, and skeletal development, avoiding excessive traction or impact. All rehabilitation exercises should be conducted under the guidance of professionals experienced in pediatric rehabilitation.
Disclaimer: This report is based on current imaging and clinical information for reference only. It cannot replace in-person consultations or professional medical advice. If there are any questions or the need to make final clinical decisions, it is advisable to consult a specialist and undergo further pathological and treatment evaluation.
Multisegmental neonatal fibrosarcoma.
