Fibromatosis of the breast
Breast fibromatosis is a very rare mesenchymal neoplasm (cell growth) which 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 which has to be treated aggressively, i.e, with surgical excision.
They can be very painful, and left untreated, they can grow large and cause unwanted cosmetic changes. Breast fibromatosis is sometimes also called a ‘desmoid tumor‘, or an ‘extra-abdominal desmoid tumor‘. Fibromatosis of the breast accounts for only about 0.2% of all primary breast tumors, however.
Here is a histology image of breast fibromatosis.
This page is getting kind of old, kind of not though, it’s still very useful… However, I have created a newer version of this page with more up-to-date information on Breast Fibromatosis.
Mesenchymal cells are stem cells
Mesenchymal cells are genetically immature or undifferentiated cells (stem cells), and this group of ‘spindle-like‘ cell lesions such as fibromatosis, myofibroblastoma, nodular fasciitis, and others, tend to be formed either from fibroblasts (immature connective tissue cells) or myofibroblasts (immature smooth muscle cells), or something in between. (This family of breast benign breast lesions are sometimes called ‘stromal‘ lesions, because they form out of ‘supportive‘ tissues, and not glands or epithelial cells.)
Breast fibromatosis is generally non-inflammatory
Breast fibromatosis might be described as an ‘infiltrating fibroblastic proliferation‘, so unlike most other lesions of this type, they have an aggressive aspect to them. Typically, fibromatosis lesions will not have an ‘inflammatory‘ element, such as plasma cells, and will often stain highly for smooth muscle actin, indicating that many of the fibroblastic cells are of ‘smooth-muscle (myo) origin.
Diagnostic imaging and pathology of breast fibromatosis
Breast fibromatosis 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 they are clinically palpable, they are often felt as a movable hard or firm mass or lump. Skin retraction and fixation to the muscle are frequently also present. Microscopically, a fibromatosis lesion will tend to show an unencapsulated infiltrative growth of evenly distributed spindle cells mixed with collagenous material. Mitosis is not common but known to occur.
Here is a mammogram image, and the fibromatosis is on the right, behind the thick skin around the nipple.
On mammogram X-ray, fibromatosis 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, and the dark area looks like a scar, but this patient never had any surgery, so the biopsy turned 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, fibromatosis can commonly be misdiagnosed following surgeries and radiation therapy for invasive breast cancers. The site of cancer surgeries radio-therapy will tend to show a ‘post-inflammatory reparative process‘, as 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 for fibromatosis of the breast
The first issue surrounding breast fibromatosis is to not ‘overestimate‘ the disease as malignant breast cancer, resulting in over treatment by full mastectomy and lymph node dissections. Assuming a definitive diagnosis of breast fibromatosis, the main concern is the high rate or recurrence with this disease. While fibromatosis does 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 recurrence. So, while short of complete removal of the breast (radical mastectomy), treating of fibromatosis still requires a 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, but since they tend to occur to a younger mean-age group than breast carcinoma, and of this group, younger women of childbearing age tend to have fibromatosis which are more ‘cellular‘, more mitotically active, with a larger amount of mild cellular atypia, it is tempting to suggest a hormonal connection. Some researchers feel that breast fibromatosis arises ‘de novo‘ from within the breast parenchyma (functional stromal elements), while others feel it instead arises de novo from the aponeurosis (layers of tendons) which overly the pectoralis major muscle, and moves into the breast parenchyma.
Lets do a few questions/answers…
- What is breast fibromatosis 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 if a wide excision is performs and resection margins are made. And recurrences are often treated with radical excision, as the primary tumor.
- What are the breast fibromatosis symptoms? Skin tethering, tender, firm, and solid-feeling.
- What is breast fibromatosis like on MRI? It is seen an irregular breast mass and MRI is often useful to show chest wall involvement in selected cases prior to surgical planning.
- What are fibromatosis causes? It remains unclear. But in some types of fibromatosis, such as desmoid tumors, it is thought that the condition may be in relation to trauma, hormonal factors, or have a genetic association. It has been reported to occur after breast implants.
- What are fibromatosis subtypes? Juvenile fibromatosis, fibromatosis colli, infantile digital fibromatosis, infantile myofibromatosis, ipofibromatosis, fibromatosis hyalinica multiplex, plantar fibromatosis, penile fibromatosis (Peyronie’s disease), and palmar fibromatosis (Dupuytren’s contracture).
- Survival rate? Because fibromatosis is not cancer, it has 100% survival.
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