Breast

Other benign tumors

Fibromatosis

Authors: Carissa LaBoy, M.D., Kalliopi P. Siziopikou, M.D., Ph.D.

Editorial Board Member: Kristen E. Muller, D.O.

Deputy Editor-in-Chief: Gary Tozbikian, M.D.

Topic Completed: 15 June 2021

Minor changes: 5 October 2021

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

PubMed Search: Breast fibromatosis[TIAB]

Page views in 2020: 7,666

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Table of Contents

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

< 0.2% of tumors of the breast
F > M, third through fifth decades
Reference: Breast Care (Basel) 2021;16:77

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

Can consequently occur after surgery, trauma or rarely, after breast implants (Breast Care (Basel) 2021;16:77, Cancers (Basel) 2020;12:1851)
Estrogen thought to influence growth (Breast Care (Basel) 2021;16:77, Indian J Surg Oncol 2020;11:71)
Can be associated with Gardner syndrome or familial adenomatous polyposis

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

Ultrasound of right breast

Mammogram of breast mass

Ultrasound of left breast

Prognostic factors

Does not metastasize (Pathologica 2019;111:344)
Locally aggressive, local recurrence rates reported in 29% to as high as 40 - 50% of cases after excision (Ann Surg Oncol 2008;15:274, J Clin Oncol 2018;36:202)
Margin status not reliable risk factor for recurrence (J Clin Oncol 2018;36:202, Cancers (Basel) 2020;12:1851)

Case reports

25 year old woman with indentation and pain in left inframammary fold (Radiol Case Rep 2018;13:1174)
31 year old woman with dimpling in the left breast (Int J Surg Case Rep 2017;41:392)
36 year old woman with rapidly growing lump in right breast (Oncol Lett 2017;14:1433)
42 year old woman with breast implants and palpable lump in left breast (Radiol Case Rep 2017;12:431)
60 year old man with 2 year history of right breast mass (Chirurgia (Bucur) 2019;114:664)

Treatment

Surgical local excision
Other options include active surveillance for asymptomatic patients and systemic therapy, such as adjuvant radiation for patients with multiple recurrences (Breast Care (Basel) 2021;16:77, Cancers (Basel) 2020;12:1851)

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

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

Cells entrapping normal ducts

Cells in collagenous stroma

Bland spindle cells

Positive margin on excision

Beta catenin positivity

Beta catenin nuclear positivity

CD34 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

Positive stains

Beta catenin (80% of cases) (Pathologica 2019;111:344)
- Not specific, can also be positive in spindle cell carcinomas, metaplastic breast carcinomas and benign phyllodes tumors (Breast Care (Basel) 2021;16:77)
SMA
Calponin

Negative stains

Pancytokeratin
p63
CD34
ER
PR
HER2
Reference: Breast Care (Basel) 2021;16:77

Molecular / cytogenetics description

Sequencing can identify activating CTNNB1 mutation or inactivating APC mutation in 79% of cases (Hum Pathol 2002;33:39, Curr Opin Oncol 2017;29:268)
Trisomies in chromosome 8 or 20 occur, significance is unknown (J Clin Oncol 2018;36:202)

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?

Cytoplasmic
Cytoplasmic and membranous
Membranous
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?

Chemotherapy is the preferred treatment due to high mitotic activity
Metastasis is a common feature of this tumor
Necrosis and pleomorphism make this a high grade tumor
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