All about Spindle cell Lipoma of the breast

A spindle cell lipoma is a rare variant of a benign breast lipoma.

So, the characteristics of a spindle cell lipoma of the breast include a mixture of:-

mature fat cells
collagen-forming spindle cells
varying degrees of myxoid change (myxoid means containing mucus)

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 a newer page with more up-to-date information on benign breast conditions, including Spindle Cell Lipoma of the Breast.

Spindle cell lipomas tend to develop in individuals over the age of 40, with an average age of around the mid-’50s.

The rate at which these lipomas develop in the breast of both men and women is approximately equal. However, overall spindle cell lipomas are much more common in men.

A bit more about the Spindle Cell Breast Lipoma

The composition of all spindle cell breast lipomas is some combination of the following cells:-

bland spindle cells
mature adipocytes
collagen bundles.

Specialists also sometimes call this type of lipoma ‘benign stromal spindle cell tumor with a predominant adipocytic component’.

Most spindle cell breast lipomas are benign, but not all of them. However, 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 of all these types of lipomas is the presence of spindle cells without epithelial cells.

Benign tumors tend to have a very bland appearance. There is a varied mixture of spindle and oval cells with bland nuclei, inconspicuous nucleoli, and a very low rate of cell mitosis. A benign spindle cell lipoma 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 features include:-

discohesive cells with mitotic activity
cell necrosis in the background
nuclear atypica
abnormal mitosis
a myxoid stromal background is also a bit more worrisome for malignancy.

‘Myxoid’ substances show an overproduction of mucopolysaccharide substances and are characterized by a loose pale-to-light staining profile. Myxoid substances appear 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 include:-

Mammogram and ultrasound evaluation

These lipomas usually appear on a mammogram as a well-circumscribed mass. On ultrasound, they will usually be seen as a homogeneously hyperechoic mass or nodule, primarily solid and with a low echogenicity shell.

Sonogram features can share some characteristics with hamartoma and other benign breast tumors, so fine needle biopsy is usually necessary for further investigation, at the very least.

Typical histological features

So, a typical lipoma with spindle cells will contain somewhat uniform spindle cells together with thick collagen bundles and mature adipocytes. Sometimes they can appear ‘entrapped’ within normal breast ducts, lobules, blood vessels, and nerves. So, this can be confusing to medics as it gives the false appearance of an aggressively infiltrating tumor.

These tumors will typically be immunoreactive to CD34 and vimentin. However, they will be non-reactive for:-

cytokeratin
S100
desmin
smooth muscle actin
Factor VIII

So this can help solidify the diagnosis.

Spindle cell breast lipomas can grow quite large

Most spindle cell breast lipomas are between 3 cm and 5 cm in diameter, but they can grow to be very large (up to 14 cm). They are composed of a relatively equal ratio of fat and spindle cells, but actually either component may predominate.

Treatment and follow-up

Given the fact that these tumors 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 a diagnosis will be possible 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 present, even to 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. However, treatment for those with a malignant or potentially malignant profile will most likely be complete surgical removal.

References

Smith, DN., Denison, CM., Lester, SC. Spindle Cell Lipomas of the Breast, A case report. Acta Radiologica 1996, Vol. 37, No. 6, Pages 893-895
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Nucci MR, Granter SR, Fletcher CDM. Cellular angiofibroma: a benign neolasm distinct from angiomyofibroblastoma and spindle cell lipoma. Am J Surg Pathol 1997, 21, 636-44