Spindle cell lipoma of the breast
A spindle cell lipoma is a rare variant of a benign breast lipoma, which is characterized by a mixture of mature fat cells, collagen-forming spindle cells, and varying degrees of myxoid change. These lesions were first described in 1975, and are most common in the subcutaneous tissue of the upper back and shoulders of males, but have been known to occur in the female or male breast as well.
This page is getting somewhat old, but don’t get me wrong, it is still very useful and I would still use it. However, I have created a newer version with more up-to-date information om Spindle Cell Lipoma of the Breast.
They tend to develop in individuals over the age of 40, with an average age of about mid-50s. The rate at which spindle cell lipomas develop in the breast of both men and women is approximately equal, but overall spindle cell lipomas are much more common in men. All spindle cell breast lipomas are composed of some combination of bland spindle cells, mature adipocytes, and collagen bundles.
Breast spindle cell lipoma is sometimes also termed a ‘benign stromal spindle cell tumor with a predominant adipocytic component‘. Most spindle cell breast lipomas are benign, but not all of them, and within the benign group, their appearance may at times mimic malignant breast cancer, so they require a thorough, conservative approach to diagnosis and management.
Potentially malignant features of spindle cell breast lipoma
One common feature to all breast spindle cell lipomas is the presence of spindle cells without epithelial cells. Benign spindle cell lipomas tend to have a very bland appearance, with varied mixtures of spindle and oval cells with bland nuclei, inconspicuous nucleoli, and a very low rate of cell mitosis. Benign spindle cell lipomas will also not show signs of necrosis.
A malignant spindle cell breast lipoma (which really means it is something else and not a spindle cell lipoma) may show a range of atypical features. These might include discohesive cells will mitotic activity, cell necrosis in the background, nuclear atypica, and abnormal mitosis. A myxoid stromal background is also a bit more worrisome for malignancy.
‘Myxoid‘ subtances show an overproduction of mucopolysaccharide substances, and are characterized by a loose pale-to-light staining profile, appearing as a thin, amorphous, and semitransparent substance. Specifically, myxoid background substances contain glycosaminoglycans, both sulphated (chondroitin sulphate, keratan sulphate) and non sulphated (hyaluronic acid).
Some features are similar to malignant breast myoepithelioma
Potentially malignant breast tumors which have similar features to breast spindle cell lipoma would include spindle cell breast carcinoma, malignant myoepithelioma of the breast, and leiomyosarcoma of the breast.
Mammogram and ultrasound evaluation of breast spindle cell lipoma
Breast spindle cell lipomas usually appear on a mammogram as a well-circumscribed mass. On ultrasound, a spindle cell breast lipoma will usually be seen as a homogeneously hyperechoic mass or nodule, primarly solid, and with a low echogenicity shell.
Sonogram features of breast spindle cell lipomas can share some characteristics with hamartoma and other benign breast tumors, so fine needle biopsy is usually recommended for further investigation, at the very least.
Typical histological features of breast spindle cell lipoma
As mentioned, a typical benign spindle cell breast lipoma will contain somewhat uniform spindle cells intermingles with thick collagen bundles and mature adipocytes. Sometimes they can appear ‘entrapped‘ within normal breast ducts, lobules, blood vessels, and nerves, which can give the false appearance of an aggressively infiltrating tumor.
Breast spindle cell lipomas will typically be immunoreactive to CD34 and vimentin but non-reactive for cytokeratin, S100, desmin, smooth muscle actin and Factor VIII, which can help solidify the diagnosis.
Spindle cell breast lipomas can grow quite large
Most spindle cell breast lipomas are between 3 and 5 cm in diameter, but they can grow to be very large (up to 14 cm). Most spindle cell lipomas are composed of a relatively equal ratio of fat and spindle cells, but actually either component may predominate.
Treatment and follow-up for spindle cell lipoma of the breast
Given the fact that spindle cell lipoma can resemble quite a large number of both benign tumors (such as myofibroblastoma of the breast and breast leiomyoma) and malignant breast tumors, (such as leiomyosarcoma) it is very unlikely that they will be diagnosed on the basis of clinical exam and mammography alone.
A fine needle biopsy is usually undertaken to get a sense of whether or not there are any of the atypical or myxoid features described above. If these features are found, even in a very small degree, a wide excisional biopsy will almost certainly be undertaken.
Benign spindle cell breast lipomas will probably be managed with routine follow-up evaluations, and those of a malignant or potentially malignant profile will most likely be completely excised surgically.
For further reading, I suggest you visit this page with some information on lipoma of the breast, go to this page with spindle cell carcinoma of the breast, as well as this page, for breast adenocarcinoma with spindle cell metaplasia.
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