Leiomyosarcoma of the breast

Leiomyosarcomas of the breast are very rare neoplasms, and can be somewhat of a challenge to diagnose.

A sarcoma is essentially cancer developing from muscle cells, while ‘carcinoma‘ refers to a cancer of epithelial cells.

Breast sarcomas account for less than 1% of breast tumors, and Leiomyosarcomas are a less common subgroup of sarcomas of the breast, representing between 2.5–6% of these.

The history and overall behavior of breast leiomyosarcoma is largely still unknown due to their low incidence rate and lack of long term follow-up.

(In most documented cases, treatment of breast leiomyosarcomas results in a cure, with potential recurrences many years after).

A breast leiomyosarcoma is one of a subgroup of ‘spindle cell‘ breast tumors which generally arise either from the smooth muscle cells lining blood vessels or from stromal mesenchymal cells.

To complicate matters further, there is quite a range in presentation and benign vs. malignant behaviors among these tumors.

Breast leiomyosarcomas are quite difficult to diagnose. Histological features can give many good clues, but often the actual diagnosis cannot be made until the tumor is surgically excised.

There is some indication that breast leiomyosarcoma may have less aggressive behavior than other types of breast sarcomas.

I just want to let you know that I have created a newer version of this page with more up-to-date information on rare breast cancers including leiomyosarcoma of the breast. However, even though this page is a little bit old, doesn’t mean you can’t still use it. It still has great research material..

Clinical presentation of breast leiomyosarcoma

A breast leiomyosarcoma will usually present as a firm breast lump, which may or may not be painful.

They tend to be slow growing tumors, and the average age for developing a breast leiomyosarcoma is around 56 years.

Breast leiomyosarcomas are generally well-circumscribed, and normally not associated with any other breast abnormalities such as deformity, nipple discharge, nipple retraction, skin dimpling, or redness (But, they may be painful).

In the early stages of presentation and diagnosis, the attending physicians will likely debate other possible diagnoses, such as a benign leiomyoma.

If a variety of indicators suggest a malignant neoplasm, likely candidates will either be a sarcoma (such as leiomyosarcoma), a poorly differentiated and unspecific ductal carcinoma, or metaplastic breast carcinoma.

Mammographic and sonographic indicators can also suggest breast fibroadenoma or possibly a phyllodes tumor, so a definitive diagnosis may take a while to determine. And of course, finding the correct diagnosis is imperative in terms of treatment and management strategies.

Differences between breast leiomyosarcoma and breast leiomyoma

Breast leiomyomas (which are benign) and breast leiomyosarcomas will both contain similar microscopic features, in particular, the prominent ‘spindle cells‘.

Also, both of these lesions may show cystic features, and both may grow to into large size tumors.

Leiomyomas of the breast will typically not, however, show significant cellular atypia, or necrosis. And, leiomyomas will not demonstrate a significant level of mitotic activity.

The general ‘rule-of-thumb‘ now is that tumors with three or more mitoses per 10 HPF are leiomyosarcomas, and those with less than three (in addition to lack of necrosis and cellular atypia) are leiomyomas.

‘Borderline‘ tumors are sometimes simply referred to as ‘smooth muscle tumors with uncertain malignant potential‘, until further investigation and follow-up determines otherwise.

Histological aspects (and diagnosis) of breast leiomyosarcoma

Cytology of breast leiomyosarcomas will typically show large, ‘malignant-looking’ dissociated epithelial-like cells.

These cells are round or elongated and with pleomorphic vesicular nuclei, prominent nucleoli, and often with a pale, poorly defined or partly elongated cytoplasm.

‘Spindle-like‘ cells with oval and blunt-ended nuclei arranged in short fascicles or bundles are often present, along with osteoclast-like giant cells, and other stromal fragments.

Numerous mitotic figures are usually present, as well as necrosis (necrosis is not always evident, however). Usually no epithelial component is identifiable in breast leiomyosarcoma, but sometimes clusters of normal ductal cells do appear.

Negative for growth factor receptors

Leiomyosarcomas of the breast is often immunoreactive for vimentin, desmin, calponin, and smooth muscle actin antibodies, but negative for S100, HMB45, CKMIX, and p63 and various other epithelial markers, and negative for hormone and growth factor receptors.

Treatments typically utilized for leiomyosarcoma of the breast

Usually, where pre- and intra-operative examinations indicate the possibility of a leiomyosarcoma, an extended excision with wide margins is performed to remove all of the affected tissue.

A metastatic workup with CT scan of the chest, abdomen, and pelvis is usually performed.

However, since lymphatic spread and nodal metastasis are not features typically associated with leiomyosarcoma neoplasms, a sentinel lymph node biopsy or axillary lymph node dissection is usually deemed unnecessary.

Axillary nodal metastasis is thought to occur in under 10% of all breast sarcomas. But since leiomyosarcomas are slow-growing malignant tumors with somewhat of a propensity for local recurrence, total or modified mastectomy tends to be the treatment of choice.

Radiation therapy may or may not be used, possibly dependent on the attainment of negative margins during surgical excision.

Some patients have been treated with chemical therapy, such as with Adriamycin, and with good results. However, since breast leiomyosarcomas are typically not hormone-dependent, hormone manipulation is not really a viable treatment option.

Typically, surgical treatments result in a cure, but leiomyosarcoma can still return, even many years later.

Return of breast leiomyosarcoma years after radiation therapy for other types of breast cancer

There is no question that the survival of women with breast leiomyosarcoma and other breast cancers have been greatly enhanced through the use of a multi-modal treatment approach.

However, there are increasing reports of sarcomas developing many years, even decades, following radiation treatments.

It should be noted, however, that either the ‘return‘ or development of breast sarcoma years after treatment is in some respects a ‘positive‘ reflection of higher and longer survival rates through the use of multi-modal therapies in the first place.

Leiomyosarcoma is the most commonly occurring sarcoma following breast cancer, representing about 22%.

Other common post-cancer breast sarcomas include malignant fibrous histiocytoma (about 15%), angiosarcoma (about 14%), and liposarcoma (about 9%).

The risk of post-radiation sarcoma is extremely low

The latency period for the development of this secondary radiation-induced sarcoma ranges from three to twenty years.

Furthermore, it can sometimes develop in patients who are in complete remission of primary breast cancer.

The ‘standardized incident ratio’ for developing a sarcoma for patients who have received radiation treatment is about 10 times that of the general population, but only slightly higher (1.3:1) than the risk for patients with breast carcinoma not receiving radiation therapy.

Overall, the risk of developing breast sarcoma following radiation treatment for breast cancer can be estimated at only around 0.5% at 15 years, so it is really quite low.

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