Fibromatosis of the breast
Breast fibromatosis is a very rare mesenchymal neoplasm (cell growth) that may occur in women, typically between the ages of 25 and 45.
It is one of a group of benign ‘spindle-cell’ proliferative lesions which are often difficult to distinguish from malignant breast cancer, especially spindle cell carcinoma.
Breast fibromatosis does not metastasize, but it may be locally aggressive and is prone to recur. So, while it is not invasive breast carcinoma, it is still a serious growth. Treatment for This condition is usually with surgical excision.
They can be very painful, and if left untreated they can grow large and cause unwanted cosmetic changes.
A ‘desmoid tumor’ is an alternative name for breast fibromatosis as is an ‘extra-abdominal desmoid tumor’. However, true fibromatosis of the breast accounts for only about 0.2% of all primary breast tumors.
Here is a Histology Image
This page is getting kind of old but it is still very useful… However, I have created a newer version of this page with more up-to-date information.
Mesenchymal cells are stem cells
Mesenchymal cells are genetically immature or undifferentiated cells (stem cells). So, this group of ‘spindle-like’ cell lesions such as fibromatosis,
Specialists also call this family of benign breast lesions ‘stromal‘ lesions, because they form out of supportive tissues and not glands or epithelial cells.
This lesion is generally non-inflammatory
Medics may also describe this condition as an ‘infiltrating fibroblastic proliferation’. So, unlike most other lesions of this type, they have an aggressive aspect to them.
Typically, these lesions will not have an inflammatory element, such as plasma cells, and will often stain highly for smooth muscle actin. This indicates that many of the fibroblastic cells are of ‘smooth-muscle (myo) origin.
The Diagnostic Imaging and Pathology of breast fibromatosis
This lesion can present a real challenge to the diagnostic team. It is virtually indistinguishable from malignant carcinoma on mammography, ultrasound, clinical exam, and gross cytological evaluation.
If the lesion is clinically palpable, it often presents as a movable hard or firm mass or lump. Skin retraction and fixation to the muscle are frequently also present.
Microscopically, these lesions will tend to show an unencapsulated infiltrative growth of evenly distributed spindle cells mixed with collagenous material. However, mitosis is not common but is known to occur.
Here is a mammogram image. The fibromatosis is on the right, behind the thick skin around the nipple.
On mammogram X-ray, this lesion will typically show an ill-defined mass of increased density in the breast parenchyma.
Breast ultrasound will tend to reveal the same irregular and ill-defined mass, hypoechoic and flat. These radiological features are basically indistinguishable from breast cancer.
There is a rare condition Fibromatosis-like carcinoma of the breast.
Here is an ultrasound image. So, the dark area looks like a scar, but this patient never had any surgery, so the biopsy turns out to be fibromatosis.
Unique difficulties in properly identifying breast fibromatosis
In the first place, the cellular (spindle-like) and mammographic appearance, along with and the rate of growth, can readily be mistaken as spindle cell carcinoma.
But secondly, these lesions can commonly be misdiagnosed for invasive breast cancers. Thus unnecessay surgery and radiation therapy may follow.
At the site of cancer surgery and radiotherapy there is often a ‘post-inflammatory reparative process’. Thus, fibrous tissue gradually develops over the wound and fat necrosis cells are gradually replaced by fibrous cells.
So, a physician could quite logically discount a developing fibrous-stromal neoplasm as ‘scar tissue’, delaying subsequent excision by many months and becoming larger in scale.
Treatment options
The first issue surrounding breast fibromatosis is to not ‘overdiagnose’ the disease as malignant breast cancer. As mentioned this can sadly result in overtreatment with full mastectomy and lymph node dissections.
Assuming a definitive diagnosis of breast fibromatosis, the main concern is the high rate of recurrence with this disease.
Whilst these lesions do not metastasize, the rate of local recurrence following excision may be as high as 27%. Because of this, surgeons will tend to leave ‘wide’, clear margins to help prevent a recurrence.
So, whilst short of complete removal of the breast (radical mastectomy), treating of fibromatosis still requires major surgery. Recent investigations as the possibility of chemical treatments of breast fibromatosis have tended to conclude that this approach would have minimal effectiveness.
Origins of fibromatosis of the breast
No one knows exactly what causes a breast neoplasm. There are no known ‘risk factors’ associated with the development of breast stromal lesions.
Hormonal imbalances are often suggested as a contributing factor in various breast-mass developments. Breast fibromatosis tends not to test positive for HER2 receptivity. However, these lesions tend to occur to a younger mean-age group of women than breast carcinoma.
Of this group, younger women of childbearing age tend to have fibromatosis which is more ‘cellular’, more mitotically active and with a larger amount of mild cellular atypia. So, it is tempting to suggest a hormonal connection.
Some researchers feel that this condition arises ‘de novo’ from within the breast parenchyma (functional stromal elements). However, other researchers feel it instead arises de novo from the aponeurosis (layers of tendons) which overlay the pectoralis major muscle and moves into the breast parenchyma.
Let’s do a few Questions and Answers…
What is the treatment?
A wide local excision with clear margins remains the treatment of choice. Recurrence rates can be fairly high, especially in those with positive margins. Recurrence is less likely to happen with wide excision and resection margins. In addition, recurrences are often treated with radical excision, as for the primary tumor.
What are the Symptoms?
Skin tethering, tender breast, firm, and solid-feeling lump.
What is breast fibromatosis like on MRI?
It appears as an irregular breast mass and MRI is often useful to show chest wall involvement in selected cases prior to surgical planning.
What are the Causes?
It remains unclear. But in some types, such as desmoid tumors, it is thought that the condition may be in relation to a trauma, hormonal factors, or have a genetic association. It has been reported to occur after breast implants.
What are the Subtypes?
- Juvenile fibromatosis
- Fibromatosis colli
- Infantile digital fibromatosis
- Infantile myofibromatosis
- Ipofibromatosis
- Fibromatosis hyalinica multiplex
- Plantar fibromatosis
- Penile fibromatosis (Peyronie’s disease)
- Palmar fibromatosis (Dupuytren’s contracture)
What is the Survival rate?
Because fibromatosis is not cancer, it has 100% survival.
Further Reading
- Found a Breast Lump? What next?
- Common Mammogram Findings
- Breast Myofibroblastoma
- Nodular Fasciitis of the Breast
- Inflammatory Fibroblastic Tumor
- Index of ALL our Articles on Benign Breast Conditions
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References
- Nakano S, Ohtsuka M, Hasegawa T. (et al). (2002) Fibromatosis of the breast: a case report. Breast Cancer 2002;9:179-183. https://www.ncbi.nlm.nih.gov/pubmed/12016400
- Povoski S, Jimenez R. (2006) Fibromatosis (desmoid tumor) of the breast mimicking a case of ipsilateral metachronous breast cancer. World Journal of Surgical Oncology 2006, 4:57 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1563468/
