Soft tissue

Fibroblastic / myofibroblastic

Fibrous hamartoma of infancy

Topic Completed: 1 July 2012

Minor changes: 4 January 2022

Copyright: 2002-2022,, Inc.

PubMed Search: Fibrous hamartoma of infancy

Komal Arora, M.D.
Page views in 2021: 5,326
Page views in 2022 to date: 236
Cite this page: Arora K. Fibrous hamartoma of infancy. website. Accessed January 19th, 2022.
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
Microscopic (histologic) 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
Microscopic (histologic) images

AFIP images

spindle cells
may infiltrate fat

pattern of
spindle cells

Primitive and
fibrous spindle
cells are bland
and uniform

Contributed by Mark R. Wick, M.D.

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
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