Soft tissue
Fibroblastic / myofibroblastic tumors
Myofibroma / myofibromatosis

Author: Deepti Reddi, M.D. (see Authors page)
Editor: Jerad Gardner, M.D.

Revised: 26 August 2016, last major update April 2013

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Myofibroma [title] soft tissue

Definition / General
  • Benign solitary (myofibroma) or multicentric (myofibromatosis) neoplasms composed of myoid cells with thin-walled blood vessels
  • Myofibroma(tosis) is in a morphologic continuum with myopericytoma and infantile hemangiopericytoma (Clin Orthop Relat Res 2010;468:917)
Terminology
Epidemiology
  • Most common fibrous tumor of infancy
  • 60% congenital, most present before 2 years of age
  • More common in males
  • Usually solitary
Sites
  • 50% of solitary myofibromas occur in cutaneous/subcutaneous tissues of head and neck region
  • Myofibromatosis involves soft tissue and bone, more frequently occurs in deep soft tissues and may involve deep viscera
Etiology
  • Unclear, rare familial cases have autosomal dominant inheritance
Clinical Features
  • Cutaneous lesions present as purple macules and resemble a vascular neoplasm
  • Subcutaneous lesions present as painless freely mobile masses
  • Deep seated lesions may be fixed
Radiology Description
  • Soft tissue lesions are either well circumscribed or infiltrative, often with calcification
  • Bony lesions occur as metaphyseal radiolucent lesions with a sclerotic margin in mature lesions
Prognostic Factors
  • Myofibromas can regress spontaneously
  • Less than 10% of myofibromas recur, and are cured by local re-excision
  • Extent and location of visceral lesions determine complications
  • In rare cases, extensive organ involvement causes death
  • Pulmonary involvement is a negative prognostic factor
Case Reports
Treatment
Gross Description
  • Median size of 2.5 cm, firm, fibrous, gray-white-brown cut surface, often central necrosis / cystic spaces with cheesy material or hemorrhage, better defined in dermis than deep soft tissue or viscera
Micro Description
  • Nodular or multinodular proliferation with zonal appearance
  • Peripheral zones have myoid short fascicles / whorls / nodules of plump myofibroblasts with pale pink cytoplasm and long, tapering nuclei with vesicular chromatin and 1 - 2 small nucleoli, but no atypia or pleomorphism, often associated with hyalinization, whorls / nodules can have a vaguely chondroid or chondromyxoid appearance
  • Central zones between the peripheral myoid nodules display cellular areas of round, polygonal or spindle cells with scant cytoplasm, hyperchromatic nuclei, arranged around thin walled branching ectatic "hemangiopericytic" vessels; often calcification, necrosis, hyalinization; often apparent subendothelial intravascular growth but still benign with minimal mitotic activity
Micro Images

Images hosted on PathOut servers:

Infantile type, courtesy of Mark R. Wick, M.D.



Solitary, adult type, courtesy of Mark R. Wick, M.D.



AFIP:

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6


Fig 1: Solitary cutaneous lesion features zones of fibrous tissue with bundles of myofibroblasts and prominent thin-walled vessels
Fig 2: High power shows interface with normal collagen
Fig 3: Biphasic with immature cells in hemangiopericytoma pattern and bundles of myofibroblastic cells
Fig 4: Central hemangiopericytic area is rimmed by hyalinized myofibroblastic area
Fig 5: Junction between myofibroblastic cells and immature spindled cells
Fig 6: Myofibroblastic spindle cells and immature cells are arranged in hemangiopericytic pattern

Images hosted on other servers:

Infant lesion, arm tumor

Poorly circumscribed nodular tumor

Well circumscribed tumor



Cellular and keloid-like areas

Intracranial tumor



Myofibroblasts around capillaries and sclerosing areas

Tumor infiltrates skeletal muscle

SMA



Fascicles of myofibroblastic cells

Smooth muscle actin+

Tumor is CD34-, desmin-; vessels are CD34+ desmin+

Resembling hemangiopericytoma

Positive Stains
Negative Stains
Electron Microscopy Description
  • Continuum from fibroblasts to myofibroblasts to smooth muscle, with prominent dilated rough endoplasmic reticulum, longitudinal filament bundles with dense bodies and focal basal lamina
Differential Diagnosis