Surgical Pathology Criteria

Fibrous Hamartoma of Infancy

Differential Diagnosis

Fibrous Hamartoma of Infancy Infantile Fibromatosis
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells Not triphasic
Primarily superficial Usually centered on muscle

 

Fibrous Hamartoma of Infancy Fibrolipoma
Poorly circumscribed Encapsulated
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells No immature component

 

Fibrous Hamartoma of Infancy Calcifying Aponeurotic Fibroma
Nodules of immature mesenchyme No immature mesenchyme
No palisaded pattern Palisaded cells around nodules
No cartilage or calcification Cartilage and calcification
Never on hands or feet Frequent on hands and feet

 

Fibrous Hamartoma of Infancy Myofibroma
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells Biphasic lesion with outer spindled cells and inner immature cells
Lacks hemangiopericytomatous vessels Hemangiopericytoma-like vessels frequent

 

Fibrous Hamartoma of Infancy Rhabdomyosarcoma
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells Not triphasic
Cytologically bland Cytologically atypical

 

Fibrous Hamartoma of Infancy Infantile Fibrosarcoma
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells Not triphasic
Mitotic figures restricted to immature foci Frequent mitotic figures

 

Fibrous Hamartoma of Infancy Inclusion Body Fibromatosis
Not reported in digits Vast majority in hands or feet
Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells Lacks triphasic pattern
No inclusions Inclusions

 

Gardner Associated Fibroma Fibrous Hamartoma of Infancy
Lacks triphasic pattern, no immature component Triphasic lesion with spindle cell fibrous areas, adipose tissue and clusters of immature mesenchymal cells
Age range 2 mo to 36 years All but rare cases congenital to 4 years

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