Adenoid Cystic carcinoma (ACC) of the breast
Adenoid cystic breast carcinoma is a rare form of breast cancer, which is named according to its microscopic appearance. Cancer cells in adenoid cystic breast carcinoma are very similar in appearance to ‘adeno’ cells (which means cells that create glandular secretions) and cystic cells. The name can be a bit confusing, as breast adenoid cystic carcinoma (ACC) is neither an adenoma, a breast fibroadenoma nor a breast cyst, which are benign, and does not arise from these conditions.
Sometimes this type of breast cancer is referred to as adenocystic breast carcinoma, and it is considered a somewhat non-aggressive type breast carcinoma with a very good chance of full recovery. With adenoid cystic breast carcinoma, lymph node involvement or metastases to distant areas is very uncommon.
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Breast adenocystic carcinoma is very rare and accounts for only about 0.2% of all breast cancers. It tends to occur in postmenopausal women from the late thirties right up into the 90s, with an average age for development between the late 50s and mid 60s. Adeno cystic breast cancer mostly effects women, but has been known to develop in men as well.
Common presenting symptoms of adenoid cystic breast carcinoma
For most women, adenoid cystic breast cancer usually presents as a mass, which is very commonly painful as well. Even though breast adenoid cystic carcinoma frequently occurs in the subareolar region, nipple discharge is actually an uncommon symptom. The breast mass tends to develop over weeks to months, and typically there is no family history of breast cancer.
Because axillary lymph node metastasis is so rare, it is important to arrive at a diagnosis early in the presentation. Early discovery through breast cancer screening is always important for a better breast cancer prognosis, but in the case of adenoid cystic breast carcinoma catching it before an unlikely metastasis provides extra assurance that the disease is fully cured. Sampling of the axillary nodes by either fine-needle aspiration or core biopsy is rarely indicated with adenoid cystic breast cancer.
Mammographic findings typical of adenoid cystic carcinoma of the breast
Adenoid cystic breast carcinoma tends to develop a palpable mass, but is also frequently discovered via mammography. However, initial screening mammograms of potential adenoid cystic breast cancer tumors can be inconclusive and screening mammography often misses the tumor.
On average, about 25%-30% of adenoid cystic breast carcinomas are discovered radiologically. Adenoid cystic breast cancer tumors will tend to appear as developing asymmetric densities or irregular masses.
On ultrasound, adenocystic breast cancers will typically appear as as irregular, heterogeneous, or hypoechoic masses with minimal vascularity on color Doppler imaging.
MRI can actually be a useful diagnostic modality with adenoid cystic carcinomas of the breast. Due to the better soft-tissue contrast and dedicated multiplanar breast sequences, the full extent of the tumor is often more clearly revealed. Calcifications may develop in adenoid cystic breast cancer tumors, but they are detected by mammography only infrequently.
Histological features characteristic of adenoid cystic breast cancer
With adenocystic breast carcinoma, traditional cytologic features of malignancy are generally not present. Tumor cells tend to be small, uniform, and monotonous, having very little cytoplasm, smooth chromatin, and just a few, if any, nuclei. The diagnosis of adenocystic breast carcinoma is usually suggested by the presence of extracellular metachromatic spheres.
Breast adenocystic carcinomas often present in multilayered clusters
Adenocystic breast cancer tumors are usually comprised of syncytial, multilayered, and branching clusters of cells with a nuclear/cytoplasmic ratio. Microscopically, adenocystic carcinoma appears highly cellular and should contain extra cellular spheres of metachromatic material surrounded by uniform cells with scant cytoplasm. Spherules of adencystic breast carcinoma are typically surrounded by several cell layers.
Adenoid cystic breast carcinoma is typically composed of basaloid cells outlining spaces containing basal-like material and of eosinophilic cells lining true glandular lumina. So, an adenoid cystic breast carcinoma lesion will typically be characterized by an invasive proliferation of circumscribed nests, and islands, and also cord-like clusters of tumor cells. These cord-like custers can form into either cribriform, tubular, or solid arrangements.
It is the ‘tumor islands‘ are which are composed of two different cell types. There is usually a basaloid cell population which predominates, and then a smaller population of cells which feature bright eosinophilic cytoplasm. In the image of an adenoid cystic breast cancer tumor above, one can observe circumscribed nests, islands, and clusters of tumor cells forming cribriform, tubular, and a few solid arrangements.
Myoepithelial origin of adenoid cystic breast carcinoma is possible, but not confirmed
The cribriform spaces or lumens of adenocystic breast carcinomas are usually filled with basement membrane material, mucoid secretions, or possibly an eosinophilic band deposited on the lumenal surface of the cells. Many adenocystic breast tumor cells contain densely packed fibrils, which might suggest a myoepithelial origin for this type of breast cancer. So while it is quite likely that the basaloid cells have a myoepithelial derivation, there is a still a lack of ultrastructural evidence to support this assertion. The smaller, eosinophilic cell populations usually show prominent desmosomes and luminal microvillous projections, and this appearance is highly suggestive of adenosquamous cells.
Often ER and PR negative
In terms of the immunohistochemical profile of adenoid cystic breast carcinoma, one usually sees a variably positive reaction for actin and S-100, while the eosinophilic components will show a positive reaction for cytokeratin. Estrogen and progesterone receptor positivity is usually negative with adenoic cystic breast cancers. That is, ER and PR receptors are usually present, but only in relatively small quantities and only in around 40% of tumors.
Grading of adenocystic breast carcinoma not based on cellular atypia
Grading of adenoid cystic breast carcinomas tends to be based on the relative amount of solid vs. cystic areas of the tumor, rather than cell atypical cellular features used to grade most other breast cancers. Grade I adenoid cystic breast tumors basically do not have a solid component, while grade II tumors have solid areas less than 30% of the total tumor mass. Adenocystic breast carcinomas in which the solid component comprises more than 30% of the total tumor are classified as grade III.
Treatment and prognosis for breast adenoid cystic carcinoma
A majority of patients with adenoid cystic breast cancer are treated with simple or modified radical mastectomy, while a minority are treated by lumpectomy. However, local excision of the tumor has shown to have an unacceptably high rates of cancer recurrence in some studies. Most patient receive radiation therapy after surgical removal of adenocystic breast cancer tumors. As the rate of metastasis for adenoid cystic breast carcinoma is known to be extremly low, (estimated at only around 2%) axillary lymph node dissection is generally not helpful in clinical management and may be avoided. When distant metastases do occur with adenocystic breast cancers, they tend to do so without any prior lymph node involvement. The lung, in fact, is by far the most common site for rare metastasis of adenoid cystic breast cancers. Not all cases of adenocystic breast carcinoma are estrogen or progesterone positive, but some do demonstrate a high level of hormone sensitivity, and can effectively treated with chemotherapy.
The prognosis for adenoid cystic breast cancer is excellent
Long term follow up is necessary with adenoid cystic breast cancer, but overall the outlook is excellent and one can have high expectations for a full recovery. Of course, the lower the tumor grade, the prognosis becomes even more encouraging. The five year disease free survival rate of adenoid cystic breast cancer is basically 100%, and the five year overall survival rate may be estimated at about 85% (most likely due to causes unrelated to breast cancer).
Below are a few common Q&A…
- What are some signs and symptoms associated with adenoid cystic breast cancer? Adenoid cystic breast carcinoma may be quite small or it can be large enough to be felt as a breast lump, which sometimes causes swelling and breast pain. The size of an adenoid cystic breast carcinoma can vary from 0.5 cm to 20 mm.
- What are some tests used to diagnose adenoid cystic breast cancer? Mammogram, breast ultrasound, breast biopsy, and/or sentinel lymph node biopsy. ACC can be effectively treated, with very little risk of recurrence, and have excellent outlook for complete recovery.
- Does adenoid cystic breast cancer spread to the lymph nodes? Most cases of adenoid cystic of the breast dos not spread to the lymph nodes and rarely metastasize to other parts of the body. Not all cases of ACC are fueled by estrogen or progesterone, but some may be hormone-sensitive.
- How is adenoid cystic breast cancer treated? Lumpectomy, mastectomy, radiation therapy, and/or hormone therapy.
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