Infantile Fibromatosis
Definition
- Bland fibroproliferative process that invades skeletal muscle, occurring age 8 and under, with two types:
- One type identical to adult desmoid fibromatosis
- Diffuse mesenchymal type, often containing fat
Alternate/Historical Names
- Aggressive infantile fibromatosis
- Cellular fibromatosis
- Congenital fibromatosis
- Diffuse mesenchymal fibromatosis
- Fibrosarcoma-like fibromatosis
- Infantile desmoid-type fibromatosis
- Lipofibromatosis
Diagnostic Criteria
- Limited to patients 8 years of age or under
- Some studies use a limit of 10 years
- Infiltration of skeletal muscle
- Involvement may be superficial
- Usually involves head, neck or thigh
- Two patterns
- Immature or diffuse pattern
- Uniform bland cells in myxoid stroma
- Nuclei round or oval to spindled
- Scant cytoplasm
- Infiltrates between muscle fibers
- Many muscle fibers remain intact
- Peripheral inflammation may be present
- May surround nerves
- May invade bone, especially in head and neck
- Fat is often present
- When prominent, the term lipofibromatosis is used
- Uniform bland cells in myxoid stroma
- Adult type is identical to adult extra-abdominal desmoid fibromatosis
- Bland spindle cells in collagenous stroma
- Variable cellularity
- Destruction of muscle with invasion
- Beta-catenin positive
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342Original posting/updates: 10/15/07, 1/26/08, 1/29/12
- Immature or diffuse pattern