Myofibroma and Myofibromatosis

 Solitary form (myofibroma)


image Multicentric form (myofibromatosis)


• Synonyms: Infantile myofibromatosis, congenital generalized fibromatosis
image Continuum with lesions termed myopericytoma and infantile hemangiopericytoma




Clinical Issues




• Most common from birth to 2 years
• Most solitary examples in subcutaneous tissues of head and neck

• Simple excision for solitary lesions

• Outcome for multicentric form is function of involved sites

image Extensive lung involvement poor prognostic factor


Microscopic




• Biphasic pattern classic
• Myoid nodules separated by cellular pockets with hemangiopericytoma-like vascular pattern

• Variable amounts of each component may be present

• Most cases have minimal atypia and mitotic activity

• Spindle cell areas

image Often prominent beneath ulcerated mucosal surfaces


Ancillary Tests




• Usually label with α-actin and calponin, but negative to focal desmin, caldesmon

• Negative for S100 and cytokeratins

• No characteristic alterations or mutations in myofibroma

• Mutations detected in PDGFRB, NOTCH3, NDRG4 in myofibromatosis


Top Differential Diagnoses




• Smooth muscle tumors

• Fibromatosis

image
Myofibroma at Scanning Magnification
This punch biopsy shows a deep-seated dermal tumor. Note the prominent lobulations and a biphasic pattern, consisting of myoid nodules image and intervening hemangiopericytomatous image zones.


image
Myofibroma With Hemangiopericytomatous Areas
This example of cutaneous myofibroma has prominent hemangiopericytomatous zones image.

image
Myofibroma, Higher Magnification of Myoid Lobules
Higher magnification shows the myoid lobules separated by more cellular areas. The myoid cells show cytoplasmic eosinophilia image.

image
Myofibroma, Hemangiopericytomatous Zone
Higher magnification shows the hemangiopericytoma-like component of a myofibroma.


TERMINOLOGY


Synonyms




• Infantile myofibromatosis, congenital generalized fibromatosis
image Continuum with lesions termed myopericytoma and infantile hemangiopericytoma


Definitions




• Benign neoplasms composed of lobules of myoid cells separated by vascularized zones (biphasic pattern)
image Solitary form (myofibroma)

image Multicentric form (myofibromatosis)


CLINICAL ISSUES


Epidemiology




• Incidence
image Solitary form rare but more common than multicentric form

image Multicentric form extremely rare

image Rare familial cases

• Age
image Wide age range (neonates to elderly)

image Most common from birth to 2 years

• Sex
image Male predominance


Site




• Most solitary examples in subcutaneous tissues of head and neck
image Trunk, extremities

image Occasional skeletal example, especially skull

• Multicentric form usually involves soft tissue and bone
image Usually long bones

image Visceral sites
– Gastrointestinal tract

– Liver, kidney, pancreas


Presentation




• Asymptomatic skin nodules with purplish color (solitary form)

• Visceral lesions with site-specific presentations

• Bone lesions seen as multiple elongated radiolucencies in metaphysis

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Myofibroma and Myofibromatosis
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