Soft tissue

Fibroblastic / myofibroblastic



Editorial Board Member: Nasir Ud Din, M.B.B.S.
Editor-in-Chief: Debra L. Zynger, M.D.
Farres Obeidin, M.D.
Borislav A. Alexiev, M.D.

Last author update: 18 January 2022
Last staff update: 14 August 2023

Copyright: 2002-2024,, Inc.

PubMed Search: Fibromatosis desmoid[title] pathology

See Also: Breast

Farres Obeidin, M.D.
Borislav A. Alexiev, M.D.
Page views in 2023: 92,119
Page views in 2024 to date: 14,905
Cite this page: Obeidin F, Alexiev B. Fibromatosis-desmoid. website. Accessed February 23rd, 2024.
Definition / general
  • Locally aggressive fibroblastic / myofibroblastic tumor arising in deep soft tissues with no metastatic potential
Essential features
  • Benign tumor with infiltrative borders and a propensity for local recurrence
  • May be associated with familial adenomatous polyposis (Gardner syndrome)
  • Histology: long, sweeping fascicles with thin walled vessels and microhemorrhages; bland cells with mild to moderate cellularity and minimal atypia
  • Immunohistochemistry: SMA+ and nuclear beta catenin+
  • Molecular: CTNNB1 and APC mutations may be seen
  • Synonyms: aggressive fibromatosis, musculoaponeurotic fibromatosis, desmoid tumor, deep fibromatosis
ICD coding
  • ICD-O: 8821/1 - desmoid type fibromatosis
  • ICD-10: D48.1 - neoplasm of uncertain behavior of connective and other soft tissue
  • ICD-11:
    • 2F7C & XH13Z3 - neoplasm of uncertain behavior of connective or other soft tissue & desmoid type (aggressive) fibromatosis
    • 2F7C & XH6116 - neoplasm of uncertain behavior of connective or other soft tissue & abdominal (mesenteric) fibromatosis
  • 37 - 50% occur in the abdominal region; shoulder girdle, chest wall and inguinal regions are the most prevalent extraabdominal sites
    • In FAP: majority (51 - 67%) are intraabdominal or in the abdominal wall
    • Sporadic: extraabdominal are more common
  • Tendency of premenopausal and pregnant women to develop fibromatosis in the abdominal wall musculoaponeurosis (Fam Cancer 2006;5:191)
Pathophysiology / etiology
  • CTNNB1 and APC gene mutations can account for up to 89% of cases (Genes Chromosomes Cancer 2010;49:560)
  • May be driven by a combination of genetic mutations, high estrogen states and antecedent trauma which leads to activation of the canonical Wnt / β catenin pathway
Diagrams / tables

Images hosted on other servers:

Canonical Wnt pathway

Site distribution

Clinical features
  • Extraabdominal tumors are deep seated, poorly circumscribed and painless
  • Abdominal wall tumors typically arise in gravid or postpartum women
  • Intraabdominal tumors arise as slowly growing, painless masses that may mimic ovarian tumors
Radiology description
  • Ultrasound:
    • Can be used with palpable masses of the extremities, abdominal, chest wall, breast, etc.
    • Oval, well to poorly marginated solid soft tissue mass with variable echogenicity
    • May have thin, linear extension along fascial planes (fascial tail sign) or intramuscular finger-like extensions (staghorn sign)
  • CT:
    • Most commonly used for intraabdominal tumors and associated complications (like small bowl obstruction)
    • Soft tissue mass with well to poorly defined margins, variable attenuation and mild to moderate enhancement
  • MRI:
    • Preferred modality for abdominal wall and extraabdominal tumors
    • Heterogeneous iso to hyperintense to skeletal muscle on T2, isointense to muscle on T1
    • Nonenhancing linear bands (Band sign) can be seen in 60 - 90% of cases
    • Moderate to marked enhancement after gadolinium based contrast (Radiographics 2016;36:767)
Radiology images

Contributed by Farres Obeidin, M.D.

Abdominal wall mass

Abdominal wall mass

Medial thigh mass

Breast mass

Paraspinal mass

Mesenteric mass

Prognostic factors
  • Local recurrence in 20 - 30%
  • Margin status shown to predict local recurrence in primary tumors but was not significant in recurrent presentations
  • Other factors such as age, gender, presentation status, tumor size, tumor focality and histologic type have shown inconsistent predictive value
  • Complete excision may cause significant morbidity and mortality in certain locations (Cancer 1999;86:2045, J Surg Oncol 2009;100:563, Ann Surg Oncol 2012;19:4028)
  • CTNNB1 S45F mutation associated with significantly increased risk of recurrence (Ann Surg Oncol 2015;22:1464)
Case reports
  • Highly variable natural course, with up to 25% undergoing spontaneous regression
  • Increasing tendency to follow with observation only (Ann Surg Oncol 2013;20:4096)
  • Mainstay of treatment is surgical resection, which can result in significant morbidity
  • Radiotherapy alone and surgery plus adjuvant radiotherapy have shown improved local control over surgery alone; however, long term effects of radiation therapy prevent standard use, especially in young patients
  • Systemic therapy for advanced disease (Oncologist 2011;16:682):
    • Antihormonal therapy (tamoxifen) can be used as first line in asymptomatic patients
    • Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown good response in some studies but no randomized trials yet
    • Several conventional chemotherapy have been assessed, doxorubicin and dacarbazine combination or pegylated liposomal doxorubicin preferred
    • Response evaluation criteria in solid tumors (RECIST) trial shows some response with receptor tyrosine kinase inhibitors; sorafenib and sunitinib may be more efficacious than imatinib but studies are ongoing
Clinical images

Contributed by Mark R. Wick, M.D.


Images hosted on other servers:

Paraspinous subcutaneous mass

Tongue mass

Gross description
  • Typically 5 - 10 cm; may be poorly defined or well circumscribed
  • Firm, glistening white, gritty and coarsely trabeculated cut surface resembling scar tissue
Gross images

Contributed by Farres Obeidin, M.D. and AFIP images

Whirling, fibrous cut surface

Gritty cut surface

Mass in the mesentery

Extension into bowel wall

Infiltrative borders

Arising in the abdominal wall muscles

Can be well circumscribed

Extraabdominal fibromatosis

Intraabdominal fibromatosis: gray glossy cut surface

Microscopic (histologic) description
  • Typically poorly defined borders
  • Conventional pattern (Am J Clin Pathol 2016;145:332):
    • Most common pattern; present at least focally in almost all tumors
    • Long sweeping fascicles with elongated, slender, spindled cells of uniform appearance and pale cytoplasm set in a collagenous stroma
    • No nuclear hyperchromasia, minimal cytologic atypia and variable mitotic rate (typically low but may be focally increased)
    • Thin walled and prominent blood vessels with perivascular edema
    • Vascular microhemorrhages may be seen
  • Hypocellular / hyalinized pattern:
    • Second most common pattern
    • More hypocellular, prominent stromal hyalinization, compressed and thin walled vessels
  • Staghorn vessel pattern:
    • ~20% of cases
    • Prominent, dilated, branching blood vessels
  • Myxoid pattern:
    • ~15% of cases
    • Myxoid stroma with less discrete fascicles; lacks the typical thin walled blood vessels
  • Keloidal pattern:
    • ~15% of cases
    • Variably sized bands of keloidal collagen fibers throughout the tumor; fascicles are disrupted and typical vascular pattern is lacking
  • Nodular fasciitis-like pattern:
    • ~10% of cases
    • Spindle to stellate cells in a loose tissue culture arrangement with variable amounts of stromal hemorrhage
  • Hypercellular pattern:
    • ~5% of cases
    • Resembles conventional pattern but with increased cellular density and frequently overlapping nuclei
    • Without cytologic atypia or nuclear hyperchromasia
Microscopic (histologic) images

Contributed by Farres Obeidin, M.D., Raul S. Gonzalez, M.D. and AFIP images

Spindling mimics dense breast fibrous tissue

Infiltrative margins

Fascicular to herringbone architecture


Bowel masses may mimic GIST

Fascicular architecture

Infiltration into muscle

Storiform or whirling architecture

Wavy, bland, spindled nuclei

Extension into GI submucosa

Bland with usually minimal mitoses

Occasional staghorn vessels

Keloid-like areas

Spindle cell proliferation with thin vessels

Mast cells

Rarely may be hypercellular

Inconspicuous nucleoli with no cytologic atypia

Extraabdominal: myxoid tumor

cellular, scattered
mitoses, none

Colonic fibromatosis

Colonic fibromatosis

extrinsic to bowel
muscularis propria

collagen seen
on trichrome


Nuclear beta catenin

Ki67 low

Cytology description
  • Bland spindle cells with long, fusiform nuclei and metachromatic matrix material
  • Tumor cells are individual or as fragments within matrix (Cancer 2007;111:166)
  • Fine needle aspiration is fairly reliable for diagnosis but core needle biopsy is better (Acta Orthop 2006;77:926)
  • May have long fascicular arrangement of spindle cells (Diagn Cytopathol 2012;40:45)
Positive stains
Electron microscopy description
  • Fibroblastic and myofibroblastic features, including intrareticular collagen fibers, thin filament bundles, cytoplasmic dense bodies
Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on other servers:

Trisomy 20 and 8

Sample pathology report
  • Abdominal wall, mass, resection:
    • Desmoid type fibromatosis (see comment)
    • Margins of resection are negative, with tumor closest at 1 cm from the inked margin.
    • Comment: Microscopic sections show a proliferation of bland spindle cells with thin blood vessels and focal areas of hemorrhage infiltrating into surrounding skeletal muscle and adipose tissue. A beta catenin immunostain shows nuclear positivity in the majority of cells, supporting the diagnosis of desmoid type fibromatosis.
Differential diagnosis
Board review style question #1

A mass was excised from the abdominal wall of a 28 year old woman. The histology is shown above. Stains were performed and the lesion shows nuclear positivity for beta catenin. Which of the following is true about this lesion?

  1. It harbors an ALK1 gene rearrangement
  2. It has high potential for recurrence if incompletely excised
  3. It has metastatic potential
  4. The lesional cells arose from the interstitial cells of Cajal
Board review style answer #1
B. It has high potential for recurrence if incompletely excised. This is a desmoid type fibromatosis. They don't have metastatic potential but have a high change for recurrence, particularly in the abdomen. GIST cells arise from the interstitial cells of Cajal in the muscularis propria of the bowel and inflammatory myofibroblastic tumors may have ALK1 gene rearrangements.

Comment Here

Reference: Fibromatosis-desmoid
Board review style question #2
Which of the following genetic syndromes is associated with an increased chance of developing desmoid type fibromatosis?

  1. Gardner syndrome
  2. Li-Fraumeni syndrome
  3. Maffucci syndrome
  4. Neurofibromatosis
Board review style answer #2
A. Gardner syndrome is an expansion of familial adenomatous polyposis (FAP) that includes additional features such as desmoid type fibromatosis, Gardner fibromas and rhabdomyosarcomas.

Comment Here

Reference: Fibromatosis-desmoid
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