Adenosquamous Carcinoma of the Breast
Adenosquamous carcinoma is a low grade breast cancer which exhibits both glandular and squamous differentiation. It is characterized by infiltrating and frequently ‘compressed‘ lumens (spaces).
It is considered a low grade subtype of metaplastic breast carcinoma, (metaplastic carcinomas are known to be characterized by the presence of non-epithelial cellular elements) and may also be referred to as a syringomatous squamous tumor.
Adenosquamous breast carcinoma is also very similar to an adenomyoma breast lesion. But a good number of breast cancer experts consider adenosquamous carcinoma of the breast to be a distinct entity. Approximately 0.3% of all cases of breast cancer will demonstrate an adenosquamous differentiation.
Adenosquamous breast carcinomas are also ‘genetically complex‘, in that some of the ‘spindle cells‘ that are quite often also found in these tumors, actually derive from epithelial components. It that sense, adenosquamous breast carcinomas may be part of an emerging group of metaplastic breast carcinomas that contain spindle cell metaplastic elements as well.
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Adenosquamous breast carcinomas are often divided into ‘low grade’ and ‘high grade’
Adenosquamous breast carcinoma is often subdivided into categories of ‘low grade‘ or ‘high grade‘. The ‘low grade‘ variant do not have any obvious nuclear anaplasia, and also tend to have a better overall prognosis.
Low grade adenosquamous breast carcinomas do not tend to metastasize, but still have been known to metastasize on occasion. ‘High grade‘ adenosquamous breast carcinoma, on the other hand, is considered to be quite aggressive, and these tumors often already have lymph node metastasis at the time of first clinical presentation.
Some breast cancer experts now assert that low grade adenosquamous carcinoma is really the same lesions as infiltrating syringomatous adenoma (of the nipple) but occuring in a different location.
Breast adenosquamous carcinomas nonetheless are rare tumors, which are basically characterized by a well-developed gland formation mixed in with solid nests of squamous cells, and all immersed in a highly cellular spindle cell stroma.
Typical low-grade metaplastic breast adenocarcinoma has a combination of components
In the image below is of infiltrative cancer tissue featuring bland cellular stroma, and the accompanying small epithelial and ductal structures. A combination of components like this would be typical of a low grade metaplastic adenocarcinoma of the breast.
Clinical and Mammographic features of Adenosquamous Carcinoma of the Breast are suggestive of malignancy
At clinical evaluation, adenosquamous carcinomas of the breast tend to be immobile, and often have an ‘ill-defined‘ margin. Skin retraction and nipple discharge is typically not apparent. On mammography, an adenosquamous breast carcinoma will often appear as an ill-defined mass with clustered microcalcifications.
An ultrasound of an adenosquamous breast lesion will usually show a mostly hypoechoic solid portion with a central low density. Both mammogram and ultrasound images will not tell you the exact type of tumor, only whether it looks like it needs a biopsy or not.
Histological features common to adenosquamous breast cancer tumors
Low grade adenosquamous breast carcinomas can often mimic benign or other low-grade malignant lesions histologically. These carcinomas typically arise in the deep breast tissue and structurally resemble the micro cystic adnexal carcinoma of the skin.
In cytological appearance, breast adenosquamous carcinomas tend to have infiltrating round to irregular tubules, which are often comma-shaped and compressed. The lumens may contain an amorphous, eosinophilic material. Myoepithelial cells typically present around the tubules in a prominent fashion, resulting in a ‘double-layer‘. The ‘squamous differentiation‘, can be variable. Between 5% to 80% of the lesions may have these squamous cell tubules.
Breast Adenosquamous carcinomas also typically have abundant collagenous stroma. On the whole, the cytology is bland. Usually there is no evidence of necrosis, and mitoses are rare.
Additional analysis of an adenosquamous breast carcinoma lesion will tend to reveal a moderate amount of epithelial cells, which are composed mostly of atypical squamous cells and with a lesser amount of atypical glandular cell groups.
The squamous component will quite often include abundant acellular keratin material, dispersed dyskeratotic cells and keratinized atypical squamous cells. The squamous cells will often line ducts that are structurally analogous to the acrosyringium of an eccrine sweat gland.
One might also find atypical epithelial ‘pearls‘ with enlarged hyperchromatic nuclei, with large, prominent nucleoli. There might also be some ductal cell clusters with enlarged and hyperchromatic nuclei with a small amount of prominent nucleoli. Microcalcifications are quite commonly found.
Adenosquamous breast carcinomas are mostly ER and PR negative
In virtually all instances of breast adenosquamous carcinoma, the tumor is negative for ER and PR receptors.
GCDFP-15 is also typically negative. But because of the myoepithelial layer present around the tubules, the lesion will test positive for smooth muscle actin and muscle specific actin.
The p63 gene (belonging to the larger p53 gene family) is quite often expressed in the basal cells of a range of myoepithelial tissues including breast tissue, and is found in approximately 95% or more of all metaplastic breast carcinomas. Usually, adenosquamous breast carcinomas will be immuno-reactive to p63 antibody assays.
Treatment and prognosis for adenosquamous breast carcinomas
Even though adenosquamous breast cancer has a low potential for metastasis, it does tend to have a high rate of local recurrence. For this reason, adenosquamous breast carcinoma lesions tend to be treated very aggressively at the local level.
Complete local excision or mastecomy is usually recommended, and it is very important to achieve clear margins. Axillary dissection may not be necessary, given the relative unlikelihood of axillary node metastasis. Usually complete excision of small lesions will provide a cure, but tumors great than 3.0 cm might require more aggressive or additional therapies.
Keep in mind, this webpage was created long ago. Although it has had some updates, they weren’t about treatment. So the treatment and survival information is out-of-date, and most certainly better now.
Everything you need to now about adenosquamous breast cancer is listed in the above information. Since this type of cancer is a rare form of metaplastic breast carcinoma, be sure to visit this page.
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