Pediatric Myofibroma

  • Etiology: Perivascular myoid-appearing spindled cell neoplasm that can be associated with PDGFRB mutations
  • Imaging:
    — Solitary in head or neck or trunk (greater than 50%)
    — Multicentric in soft tissues or bones or viscera (myofibromatosis)
    — Often in soft tissues (dermis, subcutaneous, muscle)
  • Imaging US:
    — Variable echogenicity
    — Sometimes with calcification and cystic changes
    — Often nonspecific in appearance
  • Imaging MRI:
    — T1WI: Low signal
    — T1WI post contrast: Target sign of peripheral and rim enhancement related to central necrosis
    — T2WI: Variable signal
  • DDX:
  • Complications: Visceral involvement has very poor prognosis
  • Treatment: Self-limited with rapid growth in first year and slow spontaneous regression afterwards
  • Clinical:
    — Presents as firm flesh-colored or purple nodule
    — Most common benign fibrous tumor of infancy
    — 60% in newborns and 90% in age less than 2 years

Radiology Cases of Myofibroma

MR of orbital myofibroma
Coronal T1 MRI without contrast of the orbits (left) and coronal T2 MRI (middle) shows a round soft tissue mass superior and lateral to the right orbit that is isointense on both sequences and that on coronal T1 MRI with contrast (right) is seen to enhance uniformly and intensely.
CT of myofibroma
Coronal CT without contrast of the face (above left) shows a soft tissue mass adjacent to or arising from the left mandible which on coronal CT with contrast (above right) is seen to be enhancing and well circumscribed. Coronal CT with bone windows (below) better shows the mandibular disruption and destruction caused by the mass.