Soft tissue
Fibroblastic / myofibroblastic tumors
Fibrous hamartoma of infancy

Author: Komal Arora, M.D. (see Authors page)

Revised: 18 August 2016, last major update July 2012

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

PubMed Search: Fibrous hamartoma of infancy

Cite this page: Fibrous hamartoma of infancy. website. Accessed October 27th, 2016.
Definition / General
  • Tumor-like condition in newborns to 2 year olds
  • Poorly circumscribed proliferation of immature spindle cells in organoid pattern with fat and dense fibrocollagenous tissue
  • Rare; usually age 2 years or less (25% discovered at birth), does not occur after puberty, 2/3 male
  • Usually boys
  • Axilla, shoulder and inguinal region (J Urol 1994;152:990)
  • Not hands and feet
  • Solitary, rapidly growing, freely movable mass of subcutis or dermis
Case Reports
Clinical Images

Images hosted on other servers:

Axillary tumor in 6 month old boy

Scapular tumor in 7 year old girl

Scapular tumor at surgery showing well developed capsule

Gross Description
  • Poorly circumscribed, gray-white with yellow fat, usually 5 cm or less
Micro Description
  • Poorly circumscribed, organoid with 3 components:
    • Trabecular or stellate immature mesenchymal cells with scant cytoplasm and bland straight or wavy nuclei in myxoid matrix
    • Fibrocollagenous tissue composed of bland fibroblasts or myofibroblasts
    • Mature fat; overlying epidermis usually has eccrine changes, including hyperplasia, duct dilation, intraluminal papillary formations and squamous syringometaplasia (J Cutan Pathol 2007;34:39)
  • No / scant mitotic figures
Micro Images

Images hosted on PathOut servers:

Courtesy of Mark R. Wick, M.D.

Primitive spindle cells
may infiltrate fat

Triphasic pattern of
fibrous spindle cells
delimiting islands of
mature fat and primitive
spindle cells

Primitive spindle cells
and fibrous spindle cells
are bland and uniform with
no / rare mitotic figures

Images hosted on other servers:

Three cell types

Cytology Description
Positive Stains
  • Vimentin (fibrous and mesenchyme areas)
  • Spindle cells in fibrous trabeculae may be actin+, desmin+
Electron Microscopy Description
  • Fibrous trabeculae are composed of fibroblasts and myofibroblasts, primitive mesenchymal cells have slender cytoplasmic processes with few organelles
Molecular / Cytogenetics Description
Differential Diagnosis
Additional References