Fibrosis refers to a thickening or increase in the density of breast tissue. Fibrous breast tissues include ligaments, supportive tissues (stroma), and scar tissues. Sometimes these fibrous tissues become more prominent that the fatty tissues in an area of the breast, possibly resulting in a firm or rubbery bump. Breast fibrosis is usually caused by menstrual changes, but may also develop following breast surgery or radiation therapy. Fibrosis of the breast is not associated with breast cancer and does not increase breast cancer risk.
Breast fibrosis is caused by hormonal fluctuations, particularily in levels of estrogen, and can be more acute just before the menstruation cycle begins. Some women experience occassional nipple discharge, usually dark green or brown in color. Fibrosis, along with the development of cysts, are common breast changes that may occur in women through the natural hormonal fluctuations associated with menstruation.
With breast fibrosis, the breasts may develop lumps or thickening of breast tissue. Quite often the condition is accompanined by tenderness and pain in the breast. Usually these changes occur in both breasts simultaneously, and the size of the lumps may fluctuate, which are both good clues that there is no concern of breast cancer. (breast tumors tend to occur in one breast only) . Breast fibrosis is also termed more formally as 'hyaline fibrosis of stroma', which simply means a variable increase in dense connective breast tissue. It is a very common finding, occuring in up to 7% of suspicious breast lesions examined by biopsy.
There may be some concern that breast fibrosis might 'conceal' an underlying breast carcinoma, but the evidence is strongly to the contrary. Statistically, undiagnosed breast cancers occur in less than 3% of breast fibrosis lesions sent for biopsy. As a result, most women with breast fibrosis are recommended for short-term follow up only, unless there are clearly exceptional imaging features which cannot be convincingly distinguished from a malignant tumor. In that case, a second biopsy might be recommended.
On a mammogram breast fibrosis does not have a specific appearance. The majority of breast fibrosis lesions appear as asymmetric densities. Less commonly they appear as a circumscribed mass or a concealed mass. Breast fibrosis may also appear as a lobulated or microlobulated mass, or just an architectural distortion.
With ultrasound, breast fibrosis tends to be variable and somewhat indeterminate, with about 25% showing suspicious features that might prompt a biopsy. About 75% of breast fibrosis lesions are visible to ultrasound, and the majority do appear as a moderately well-defined hypochoic mass, but they may also appear as either an ill-defined mass or simply as marked shadowing without any visible mass.
Microscopically, breast fibrosis tends to form into either a 'mass-like' fibrosis, nodular-fibrosis, or simply a 'haphazard' fibrosis. The 'mass-like' cellular configuration tends to feature dense fibrous tissue in which ductal and lobular elements are 'entrapped', dialted, or completely absent. The 'nodular' pattern of breast fibrosis will tend to demonstrate a discrete lobulocentric focus of fibrous tissue, while a 'haphazard' organization would typically show irregular patches of fibrous tissue admixed with fat tissue.
Breast fibrosis does not increase risk for breast cancer in any way, and does not need to be treated. However, it is a good idea to have any breast lumps checked out by your doctor, particularly if it is the first time that breast lumps have been noticed. Some medications can help control symptoms when fibrosis is associated with hormonal changes.