Myofibroma, Solitary and Multicentric

Differential Diagnosis

Infantile hemangiopericytoma
We consider this to be the same tumor as myofibroma

Glomangiopericytoma and myopericytoma It has been proposed that these two tumors and myofibroma are part of the same spectrum

Myofibroma	Glomangiopericytoma and Myopericytoma
Small primitive cells present	Lacks small primitive component
Lacks perivascular pattern	Perivascular distribution

Some overlap may occur

Myofibroma	Inflammatory Myofibroblastic Tumor
90% <2 years	Usually age 0-14 years
Biphasic nodules with immature cells	No immature cells
Hemangiopericytomatous vessels	No HPC like vessels
Rare in abdomen	Frequent in abdomen

Myofibroma	Infantile Fibrosarcoma
Random spindle cell pattern	Fascicular pattern
Biphasic mature and immature areas	No biphasic pattern
Atypical mitotic figures rare	Atypical mitotic figures common

Solitary Fibrous Tumor	Myofibroma
Lacks biphasic nodular pattern	Biphasic nodular pattern
CD34 >95% positive	CD34 negative
Actin focal, rare	Actin positive
Multiple lesions uncommon	25% of cases multifocal
Rare in infants	Rare over age 2 years

Both frequently show a hemangiopericytoma-like vascular pattern

Hemangiopericytoma	Myofibroma
Rare under age 20 years	Rare over age 2 years
Lacks biphasic nodular pattern	Biphasic nodular pattern
CD34 50% positive	CD34 negative
Actin focal, rare	Actin positive
Multiple lesions uncommon	25% of cases multifocal

Both frequently show a hemangiopericytoma-like vascular pattern

Leiomyoma	Myofibroma
Lacks biphasic pattern	Biphasic nodular pattern
Lacks HPC-like vascular pattern	Frequent HPC-like vascular pattern
Multiple lesions uncommon	25% of cases multifocal
Desmin variable	Desmin negative

Nodular Fasciitis	Myofibroma
Lacks biphasic pattern	Biphasic nodular pattern
Lacks HPC-like vascular pattern	Frequent HPC-like vascular pattern
Multiple lesions rare	25% of cases multifocal
Desmin variable	Desmin negative

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
Rare mitotic figures	Frequent mitotic figures

Myofibroma	Inclusion Body Fibromatosis
Rare on digits	Usually on digits
Biphasic nodules with central primitive cells	Lacks primitive cells and perivascular clustering of cells
No inclusions	Inclusions

Myofibroma	Plexifiorm Fibrohistiocytic Tumor
Circumscribed	Plexiform rays infiltrate fat
Central primitive dark cells with hemangiopericytoma-like vessels	Nodules with histiocyte-like cells and multinucleated cells