Breast

Other benign tumors

Fibromatosis



Topic Completed: 15 June 2021

Minor changes: 5 October 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Breast fibromatosis[TIAB]

Carissa LaBoy, M.D.
Kalliopi P. Siziopikou, M.D., Ph.D.
Page views in 2020: 7,666
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Cite this page: LaBoy C, Siziopikou KP. Fibromatosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/breastfibromatosis.html. Accessed October 21st, 2021.
Definition / general
  • Low grade infiltrative spindle cell neoplasm composed of fibroblasts and myofibroblasts
Essential features
  • Rare low grade neoplasm with infiltrative pattern
  • Bland spindle cells arranged in long intersecting fascicles within a collagenous stroma
  • Characterized by alterations in WNT / beta catenin pathway
  • Does not metastasize but can locally recur after surgical excision
Terminology
  • Desmoid tumor, aggressive fibromatosis, desmoid type fibromatosis, extra-abdominal desmoid
ICD coding
  • ICD-O: 8821/1 - desmoid type fibromatosis
  • ICD-11: 2F75 & XH13Z3 - neoplasms of uncertain behavior of breast and aggressive fibromatosis
Epidemiology
Sites
  • May be primary to the breast or be secondary extension into the breast from the chest wall
Pathophysiology
  • Up to 95% harbor CTNNB1 activating mutation (sporadic); APC gene inactivating mutation responsible for remainder of cases (hereditary) (Cancers (Basel) 2020;12:1851)
  • Through the WNT / beta catenin pathway, these mutations motivate cells to proliferate while destabilizing beta catenin that then accumulates within the nucleus (J Clin Oncol 2018;36:202)
Etiology
Clinical features
  • Slow growing, often self detected firm mass
Diagnosis
  • May arise as palpable mass that appears as abnormality on mammography
  • Rarely presents with breast pain, nipple discharge and skin retraction (Breast Care (Basel) 2021;16:77)
Radiology description
  • Imaging may show well circumscribed mass or poorly defined / spiculated mass that can be mistaken for malignant process (Breast Care (Basel) 2021;16:77)
Radiology images

Contributed by Carissa LaBoy, M.D.
Mammogram of right breast

Mammogram of right breast

Ultrasound of right breast

Ultrasound of right breast

Mammogram of breast mass

Mammogram of breast mass

Ultrasound of left breast

Ultrasound of left breast

Prognostic factors
Case reports
Treatment
Gross description
  • Well to poorly circumscribed mass of variable size (from < 1 cm to > 10 cm), with white-gray whorled or trabeculated cut surface
Gross images

Images hosted on other servers:

White trabeculated cut surface

Missing Image

Chest wall mass

Frozen section description
  • Bland spindle cells seen on intraoperative frozen section would prompt benign diagnosis
Microscopic (histologic) description
  • Long intersecting fascicles composed of bland spindle cells with indistinct borders, hyperchromatic nuclei with occasional nucleoli and eosinophilic cytoplasm
  • Cells infiltrate normal ducts and lobules, adipose tissue and skeletal muscle, thus mimicking invasive process
  • Mitosis is rare
  • Background stroma has thickened collagen resembling keloid
  • Older lesions may calcify
  • Lymphoid aggregates may be seen at the periphery of the lesion
  • Reference: Pathologica 2019;111:344
Microscopic (histologic) images

Contributed by Carissa LaBoy, M.D.
Infiltrative breast mass

Infiltrative breast mass

Cells entrapping normal ducts

Cells entrapping normal ducts

Cells in collagenous stroma

Cells in collagenous stroma

Bland spindle cells

Bland spindle cells

Positive margin on excision

Positive margin on excision


Beta catenin positivity

Beta catenin positivity

Beta catenin nuclear positivity

Beta catenin nuclear positivity

CD34 negative spindle cells

CD34 negative spindle cells

Pancytokeratin negative spindle cells

Pancytokeratin negative spindle cells

Virtual slides

Images hosted on other servers:

Fibromatosis in the breast

Cytology description
  • Fine needle aspiration is difficult and often yields fibrous nondiagnostic material
  • When successful, fine needle aspiration shows bland spindle cells with hyperchromatic nuclei and wispy cytoplasm within abundant stroma (Cancer 2007;111:166)
Cytology images

Images hosted on other servers:

Fine needle aspiration of fibromatosis

Fine needle aspiration of fibromatosis

Positive stains
Molecular / cytogenetics description
Videos

Review of fibromatosis

Sample pathology report
  • Left breast, needle localized lumpectomy:
    • Fibromatosis, measuring 2.8 cm in greatest dimension
    • Margins negative with tumor > 0.5 cm from all margins
Differential diagnosis
  • Scar:
    • Focally infiltrative lesion composed of bland spindle cells with associated histiocytes, foreign body giant cell reaction and lymphocytes
    • History of prior procedure
  • Nodular fasciitis:
    • Focally infiltrative lesion composed of spindle cells forming short fascicles or storiform pattern with increased mitotic activity
    • Does not display nuclear beta catenin staining
  • Dermatofibrosarcoma protuberans:
    • Focally infiltrative lesion with spindle cells in storiform growth pattern and low mitotic activity
  • Low grade fibromatosis-like metaplastic carcinoma:
    • Infiltrative lesion composed of spindle to epithelioid cells arranged in small clusters with low mitotic activity
    • Cytokeratin and p63 positive
  • Low grade myofibroblastic sarcoma:
    • Focally infiltrative lesion composed of spindle cells arranged in fascicles
    • Mild to moderate nuclear pleomorphism and brisk mitosis
  • Myofibroblastoma:
    • Spindle cells arranged in short, disorganized fascicles with intersecting thick collagen bands resembling keloid; do not typically entrap normal ducts or lobules
  • Benign phyllodes tumor:
    • Well circumscribed mass with hyperplastic epithelium within a hypercellular stroma composed of spindle cells with mild atypia and low mitotic activity
Board review style question #1

What is the pattern of beta catenin immunohistochemical staining for fibromatosis pictured above?

  1. Cytoplasmic
  2. Cytoplasmic and membranous
  3. Membranous
  4. Nuclear
Board review style answer #1
D. Nuclear. The pathophysiology of fibromatosis involves an activating CTNNB1 mutation in sporadic cases and an APC gene inactivating mutation in hereditary cases. Both types of mutations activate the WNT / beta catenin pathway, motivating cells to proliferate while degrading beta catenin, which then accumulates within the nucleus. This in turn yields a nuclear pattern of staining by immunohistochemistry.

Comment Here

Reference: Fibromatosis
Board review style question #2
Which of the following is correct regarding the histologic features and clinical behavior of breast fibromatosis?

  1. Chemotherapy is the preferred treatment due to high mitotic activity
  2. Metastasis is a common feature of this tumor
  3. Necrosis and pleomorphism make this a high grade tumor
  4. Tumor has a high frequency of local recurrence
Board review style answer #2
D. Tumor has a high frequency of local recurrence. Breast fibromatosis is a low grade tumor consisting of bland spindle cells with rare or no mitotic activity and no metastatic potential. However, due to its infiltrative nature, this tumor has a tendency to locally recur after surgical excision.

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Reference: Fibromatosis
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