Nodular fasciitis in the breast
Nodular breast fasciitis is a benign, small, fibrous cellular growth, which often grows as a mesenchymal (stem cell) reaction to an injury. Other commonly used named for the condition are subcutaneous pseudosarcomatous fibromatosis, and pseudosarcomatous fibromatosis.
They tend to grown on the subcutis, which is a layer of connective tissue beneath the dermis. As such, they are more of a ‘skin‘ issue and not really related to breast cancer at all. In rare instances they may develop on the breast or be discovered in a screening mammogram, but this can likely be traced to trauma or injury. The development of nodular breast fasciitis can ‘resemble‘ malignant cell processes, so really it is an issue of a proper, benign differential diagnosis.
Breast nodular fasciitis may grow quickly
Nodular fasciitis can grow anywhere, particularly on the neck, trunk, and the upper extrememties. They are small lesions but they grow very rapidly, usually over just a few weeks. They can occur at any age , but are most common in young adults with a peak age of 40 years. When palpable, they are often described as ‘elastic-hard‘ and ‘movable‘.
Diagnostic imaging and histological characteristics of nodular breast fasciitis
Histologically, a nodular fasciitis lesion will tend to show characteristic ‘spindle-like‘ cells, and many of these proliferating spindle cells with have features of myofibroblasts. The ‘spindle‘ appearance of these cells bears a close resemblence to spindle cell carcinoma, and that it why they are sometimes misdiagnosed. In addition to the spindle cells, nodular fasciitis will often feature wide bands of collagen and vascular (blood vessel) proliferation. Lymphocytes are also frequently encountered. (Lymphocytes are a kind of white blood cell that functions as antibodies against injury and infection).
Nodular fasciitis also can show a certain degree of cell mitosis and ‘cellularity‘ (large amounts of cells and many different types of cells), which can also raise suspicions of malignancy, even though they are benign. However, if the lesion shows cells which are very large and with atypical hyperchromatic nuclei, that would suggest a more malignant situation and possible association with breast cancer.
Nodular fasciitis of the breast can be misleading on an X-ray
Radiologically, nodular fasciitis can be a bit confusing initially as they can show ‘infiltrative‘ margins. (smooth, well-defined margins are most commonly associated with benign growths, irregular margins are more suspicious of malignancy) Nodular fasciitis tumors can show spiculted margins, but they tend not to have calcification. Sonogram can also be a bit vague, and nodular fasciitis will tend to show a relatively homogeneous hypoechoic, solid mass with a border often obscured by normal tissues.
Sometimes MRI is also used for imaging studies, which can give a very indication of the irregular shape of the lesion, but still cannot rule of malignancy. Biopsy is almost always required. Essentially harmless, these lesions are often just let be, unless they grow very quickly or begin to show other unexpected changes on follow-up breast evaluations and breast cancer screenings.
Some Q and A that will disappoint.
- What about recurrence after excision? Sometimes, not always, it can return in the scar from removing it.
- Is there genetics involved? Yes, but usually not.
- What are the symptoms? A thickening, a lump, a raised streak below the skin, etc.
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