infantile fibrosarcoma

Infantile fibrosarcomas are locally aggressive rarely metastasizing fibroblastic tumors found in the pediatric population.

Terminology

Other acceptable terms include congenital fibrosarcoma, infantile fibrosarcoma-like tumor, cellular congenital mesoblastic nephroma .

Epidemiology

Infantile fibrosarcomas are most commonly found in the first two years of life with more than 75% of the cases found during the first year and at birth and further 15% in the second year of life . A bit less than 15% are already detected at prenatal ultrasound .

Associations

There is a relation to congenital mesoblastic nephroma .

Clinical presentation

The typical manifestation is a rapidly growing painless mass or nodule, they may look like a vascular tumor and ulcerate .

Pathology

Infantile fibrosarcomas are locally aggressive tumors characterized by spindle cells or primitive ovoid cells often growing in a fascicular or herringbone architecture with a staghorn vascular pattern, mixed inflammatory changes and .

Location

Infantile fibrosarcomas are usually found in the superficial and deep soft tissues of the following locations :

  • extremities
  • trunk
  • head and neck region

Less commonly it is found in the abdomen or retroperitoneum and rarely it involves the bones and viscera such as the lung and the bowel .

Macroscopic appearance

Macroscopically infantile fibrosarcomas usually appear as poorly circumscribed lobulated tumors with infiltrative boundaries, some feature a pseudocapsule. They can be quite large when discovered. .

Microscopic appearance

The microscopic spectrum of infantile fibrosarcoma is broad and includes the following :

  • monomorphic spindle cells to ovoid/round cells
  • fascicular growth in a ‘herringbone’ architecture
  • collagenous or myxoid background
  • hemangiopericytoma-like vascular pattern
  • mixed chronic inflammatory infiltrates
  • variable mitotic activity
  • frequently zonal necrosis and/or hemorrhages
Immunohistochemistry

Immunohistochemistry stains are non-specific and can display expressions of SMA, CD34, S100 or desmin .

Genetics

Infantile fibrosarcoma often displays an ETV6-NTRK3 gene fusion or rearrangement .

Radiographic features

Imaging findings usually reveal a nonspecific heterogeneous mass with signs of intralesional hemorrhage .

Ultrasound

Ultrasound usually reveals a heterogeneous isoechoic, hypervascular mass with dilated vessels sometimes looking a bit like hemangioma .

MRI

On MRI infantile fibrosarcomas are heterogeneous soft tissue masses and can show well-defined or infiltrative tumor margins. They might show low signal intensity fibrous streaks . They might show with intralesional signal voids due to vasculature and hemorrhagic components, being hyperintense in both T1 weighted and T2 weighted images .

Signal characteristics are usually as follows:

  • T1: generally hypo- to isointense to muscle
  • T2: generally hyperintense signal intensity
  • T1 C+ (Gd): heterogeneous predominantly peripheral enhancement

Radiology report

The radiological report should include a description of the following:

  • form, location and size
  • tumor margins
  • relation to the muscular fascia
  • relationship to local nerves and vessels
  • relations to other organs

Treatment and prognosis

Treatment options include combinations of surgery and chemotherapy. Local recurrence occurs in up to 40% and is especially associated with incomplete resection. Metastases occur rarely and most often affect the lungs. The 10-year survival is about 90% with standard therapy .

Differential diagnosis

Conditions which can mimic the presentation and/or the appearance of infantile fibrosarcoma include :

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