Soft tissue
Fibroblastic / myofibroblastic
Mammary-type myofibroblastoma

Topic Completed: 1 April 2013

Minor changes: 16 September 2020

Copyright: 2002-2020,, Inc.

PubMed: Mammary-type myofibroblastoma

Deepti Reddi, M.D.
Jerad M. Gardner, M.D.
Page views in 2019: 2,439
Page views in 2020 to date: 2,498
Cite this page: Reddi D. Mammary-type myofibroblastoma. website. Accessed October 24th, 2020.
Definition / general
  • Benign myofibroblastic lesion with hyalinized collagenous stroma and often adipose tissue, identical to breast lesion (see Breast-nonmalignant chapter)
  • May be closely related to cellular angiofibroma and spindle cell lipoma (Mod Pathol 2011;24:82)
  • Median age 55 years, 80% men
  • Usually inguinal / groin region or along milk line, also abdominal wall, buttock, back, vaginal wall
  • Usually subcutis, but may be deeper
  • Case report in the ovary (Mod Pathol 1999;12:907)
Clinical features
Case reports
  • Excision, does not appear to recur
Gross description
  • Median 6 cm, unencapsulated but well circumscribed, firm, white-pink-tan-brown, nodular or whorled cut surface
Gross images

Images hosted on other servers:

Well circumscribed lesion
with white whorled cut surface

Microscopic (histologic) description
  • Identical to breast lesion mammary myofibroblastoma
  • Sheets or short fascicles of myofibroblastic spindle cells with eosinophilic to amphophilic cytoplasm and poorly defined borders
  • Oval to tapered nuclei with fine chromatin and small nucleoli, nuclei often arranged in parallel arrays or vague palisades similar to spindle cell lipoma
  • Stroma has haphazard thick bundles of collagen
  • May have epithelioid features (Am J Surg Pathol 2009;33:1085), focal nuclear atypia with enlarged nuclei or multinucleation, small vessels with perivascular lymphocytes, prominent adipose tissue with scattered mast cells, low mitotic activity (but no atypical mitotic figures) (Arch Pathol Lab Med 2008;132:1813)
Microscopic (histologic) images

AFIP images

Circumscribed border

Fascicles of spindle cells separated by dense collagen bundles

Images hosted on other servers:

Scattered mast cells


Cytology description
  • Abundant random single and clustered benign spindle mesenchymal cells with scant cytoplasm and elongated or oval nuclei with finely granular chromatin and inconspicuous nucleoli (Diagn Cytopathol 2004;30:406)
Cytology images

Images hosted on other servers:

Loose groups of cells with abundant
eosinophilic granular cytoplasm and bland nuclei

Positive stains
Molecular / cytogenetics description
Differential diagnosis
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