Acinic cell breast carcinoma

Acinic cell breast carcinoma has only been recognized since the 1990s. This type of cancer is often found in the parotid (salivary) gland, however, in this case, it is a similar tumor but in the breast.

Another way to view this disease is as a generic invasive ductal carcinoma which shows features of acinic cell differentiation, similar to those encountered in homologous tumors of salivary glands.

So, acinic cell breast tumors have been known to affect women between the ages of 35 and 80 years old. The average age of development is usually around 56 years of age.

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Clinical and mammographic presentation of acinic cell breast tumors

Acinic cell breast tumors will usually range in size from 2 to 5 cm at the time of presentation. Furthermore, most of the time, this type of tumor will present as a palpable breast nodule (in other words, a breast lump that you can feel).

On a mammogram, this type of lesion will usually appear as an ill-defined mass.

What are the Histological Characteristics?

Histologically, acinic cell breast carcinoma will tend to show a micro glandular pattern merging with solid areas. However, the histological pattern remains somewhat variable.

Most acinic cell breast tumors will have infiltrative margins, occasionally surrounded by a thin fibrous pseudocapsule. Often acinic cell carcinomas of the breast will be predominantly made up of a monotonous proliferation of cells with a fine granular cytoplasm. In some cases, however, the neoplastic cells may have a clear cytoplasm.

Cellular appearance may be similar to micro glandular adenosis

The arrangement of neoplastic cells (or cancer cells) in acinic cell breast cancer tends to be in small, glandular structures which are somewhat similar to micro glandular adenosis and solid nests.

The distribution of glands in this type of carcinoma tend to be haphazard and in a dense fatty and fibrous stroma. The glands are often round and irregular in shape with a lining of a single layer of columnar cells.

Neoplastic cells in breast acinic cell carcinomas tend to be cuboidal to columnar in shape. The cancerous cells also have well-defined boundaries.

Neoplastic malignant cells also tend to contain moderate to abundant amounts of eosinophilic to amphophilic granular cytoplasm. Nuclei of the cancer cells in breast acinic cell carcinomas tend to be irregular and round or oval. They will quite often show a thick nuclear membrane, and will also have prominent nucleoli.

The amount of cell mitoses is variable. Most of the time it seems to be low in breast acinic cell carcinomas, but in select cases, the amount of mitotic activity may be moderate to high.

Immunohistochemical aspects of breast acinic cell carcinomas

Dense eosinophilic PAS-diastase-positive materials are quite often evident within the glandular lumina of acinic cell breast carcinomas. Most neoplastic cells in acinic cell breast carcinomas will stain intensely with:-

anti-amylase
anti-lysozyme
anti-a1-antichymotrypsin
anti-epithelial membrane antigen
anti-S100 protein antisera (most often acinic cancer will stain)

A moderate number of acinic cell breast tumors will also test positive for the GCDFP15 antibody, which is a marker of apocrine differentiation in breast cancer tumors.

Estrogen, progesterone and androgen receptors consistently test negative in acinic cell carcinomas of the breast.

Certain immunohistological ‘markers’ confirm an acinic cell carcinoma

Zymogen-type granules are typically present within the cytoplasm of the abnormal cells in acinic cell (serous) carcinomas of the salivary gland.

Doctors examining a type of breast tumor may also look for:-

amylase
lysozyme
a1-antichymotrypsin

The above are all normal constituents of salivary gland acinar cells. So, when all or most of these markers are found in a primary breast cancer tumor, it confirms an acinic cell differentiation or acinic cell breast carcinoma.

Treatment and Prognosis for Acinic Cell Carcinoma of the Breast

There are really too few cases of breast acinic cell carcinoma to make firm generalizations about prognosis. The significance of breast carcinoma with acinic cell differentiation remains unclear.

However, within the limited number of cases to date, it appears that this type of cancer has a favorable prognosis. Specialists consider acinic cell carcinoma to be a slow-growing form of breast cancer.

The treatment for acinic cell carcinoma is usually by wide local excision or mastectomy. In addition, doctors may prescribe systemic breast cancer therapies.

The prognosis for acinic cell cancer of the salivary gland is very positive. There is a 5 year survival rate of almost 90% and a 20-year survival rate of just under 60%.

It is not always appropriate to assume that breast cancers will behave in a similar fashion to similar cancer types in other areas of the body.

The few statistics that are available on this type of breast cancer, suggest that the above approximate survival rates are a reasonable estimate of the outlook for acinic cell carcinoma of the breast.

Some patients do experience local and systemic recurrences, but a vast majority of patients are alive and disease-free five years after the initial breast cancer diagnosis.