Soft tissue

Fibroblastic / myofibroblastic


Inclusion body fibromatosis

Last author update: 1 July 2012
Last staff update: 26 July 2023

Copyright: 2002-2023,, Inc.

PubMed Search: Inclusion body fibromatosis

Komal Arora, M.D.
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Cite this page: Arora K. Inclusion body fibromatosis. website. Accessed October 3rd, 2023.
Definition / general
  • Dermal fibroblastic and myofibroblastic lesion with cytoplasmic eosinophilic inclusions, usually in digits of infants
  • Also called infantile digital fibromatosis, infantile digital fibroma (J Hand Surg Am 1995;20:1014)
  • Distinct lesion from classic fibromatosis (Am J Surg Pathol 2009;33:1)
Clinical features
  • Rare; lesions usually present at birth or in first 2 years
  • Similar lesions in adults
  • Often are multiple
Case reports
Clinical images

Contributed by Mark R. Wick, M.D.

Images hosted on other servers:

Various images

Gross description
  • Nodules with stretched overlying skin, lesions are ill defined, white-tan, usually 2 cm or less
  • No hemorrhage or necrosis
Microscopic (histologic) description
  • Nonencapsulated, dermal proliferation of hypocellular sheets or fascicles of fibroblasts and myofibroblasts with variable collagen
  • Some spindle cells have peculiar eosinophilic (hyaline) cytoplasmic inclusions the size of a lymphocyte nucleus
  • Usually mitotic figures
  • May infiltrate into adjacent tissue
  • No atypia
Microscopic (histologic) images

Contributed by Mark R. Wick, M.D. and AFIP


Fibroblastic cells

Cells are bland and monomorphic

Inclusions resemble red blood cells

Cytoplasmic inclusions

Various images

Images hosted on other servers:

Various images

Cytology description
Positive stains
Negative stains
Electron microscopy description
  • Spindle cells are myofibroblasts with rough endoplasmic reticulum and free lying inclusions composed of compact masses of actin granules and filaments without a limiting membrane (Am J Pathol 1979;94:19)
Differential diagnosis
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