Mucinous cystadenocarcinoma of the breast
Mammary mucinous cystadenocarcinoma (MCA) is a rare type of invasive breast cancer that derives its name due to having a virtually identical morphologically to mucinous cystadenocarcinoma of the pancreas, appendix, or ovary. It is basically a malignant presentation of a normally benign cystadenoma (or ‘cystoma’), which is a type of cystic adenoma. Mucinous cystadenocarcinoma of the breast is distinct from the more common ‘mucinous‘ or ‘colloid‘ breast carcinoma, and is also distinct from cystic hypersecretory carcinoma of the breast.
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These tumors also must be differentiated from metastasis of cancer cells from other sites. Mammary mucinous cystadenocarcinoma is composed primarily of tall columnar cells with abundant intracytoplasmic mucin. Unlike ordinary mucinous carcinoma, primary mucinous cystadenocarcinoma of the breast usually demonstrates both intracellular and extracellular mucin, whereas in mucinous breast carcinoma the malignant cells are suspended in extracellular mucin.
Mucins are various glycoproteins in connective tissue, saliva, mucus, etc., that lubricate and protect the body. Mucinous breast carcinomas usually appear as ‘islands‘ of malignant cells suspended within ‘lakes‘ of mucous.
Average age for development of Mucinous cystadenocarcinoma of the breast is about 50
It is believed that mucinous cystadenocarcinoma of the breast arises from mucinous metaplasia and macrocystic transformation of ordinary breast carcinoma (Invasive ductal carcinoma NOS). The average age for developing mucinous cystadenocarcinoma of the breast is in the late 50’s and does seem a bit more common in older women. Breast mucinous cystadenocarcinoma is highly invasive, but, still tends to be associated with a positive prognosis.
Mammographic features common to mucinous cystadenocarcinoma of the breast
Mammographic and ultrasonographic images of breast mucinous cystadenocarcinoma tend to be indistinguishable from more common mucinous carcinoma (colloid carcinoma) of the breast. Commonly, one sees a well defined, possibly multilobular tumor with often does not have spiculated margins or intralesional microcalcifications.
Histological features associated with breast mucinous cystadenocarcinoma
Microscopically, mucinous cystadenocarcinomas of the breast are characterized by abundant extracellular and intracellular mucin, and looks very much like a mucinous cystic neoplasm of the pancreas or ovary. One often finds a ‘transition‘ between ordinary infiltrating ductal carcinoma or DCIS and the mucinous cystadenocarcinoma, which suggests that breast mucinous cystadenocarcinoma derives from a metaplasia process of ordinary DCIS.
Typically, biopsy samples of breast mucinous cystadenocarcinoma have to be large, as it is easy to misinterpreted mucinous cystadenocarcinom as a benign lesion. Biopsy specimens often contain just a few tumor cells with bland-appearing nuclei. Cystic spaces of variable sizes are typically observed, lined with predominantly blandappearing columnar mucinous cells with stratification, tufting, and papillary formations. Varying degrees of cytologic atypia are usually evident, and atypical cells generally contain intracytoplasmic mucin.
Immunohistochemical markers for mucinous cystadenocarcinoma of the breast
A primary mucinous cystadenocarcinoma of the breast will usually express ER and PR (estrogen and progesterone receptor positive) along with CK7 and cdx2 (Progesterone is less-reliably positive). Also, one might see a strong membranous HER2-protein expression and HER2-gene amplification. Immunoreactivity for MIB-1 (Ki-67) is also present in a relatively high percentage of tumor cells. Mucinous cystadenocarcinomas of the breast are quite often negative for C-erb-B2 receptors.
Cumulative immunohistochemical findings for mucinous cystadenocarcinoma of the breast suggest that these breast tumors can develop independently of estrogenic stimulation. Unlike mucinous cystadenocarcinoma of the ovary and pancreas which are positive for both CK7 and CK20, breast mucinous cystadenocarcinoma tends to be positive for CK7 but negative for CK20. Occassionaly one finds a neuroendocrine differentiation in mucinous cystadenocarcinomas of the breast, and that can usually be demonstrated through the expression of chromogranin.
Prognosis and treatment for breast mucinous cystadenocarcinoma
Although breast mucinous cystadenocarcinomas tend to show high proliferative activity, the prognosis is generally favorable, even with tumors of a large size. Axillary lymph node metastasis occurs in the order of 20% of patients, but unlike generic invasive ductal carcinoma, lymph node metastasis is not really associated with a poor prognosis in breast mucinous cystadenocarcinomas.
Usually treated by mastecomy with lymph node dissection
Most patients are treated with full or partial mastecomy along with axillary node dissection. Depending on the size and location of the tumor, a lumpectomy is possible in a minority of cases. Due to the ER positivity usually associated mucinous cystadenocarcinoma of the breast, chemical therapy using tamoxifen is frequently administered. Some patients also receive post operative radiation therapy. Local recurrence is rare.
For further reading, I suggest you visit this page, which has information on Mucinous (or Colloid) carcinoma.
Below are a few common Q&A regarding Mucinous carcinoma…
- What is mucinous carcinoma made up of? This type of cancer is a tumor made up of abnormal cell that float in pools of mucin, a key ingredient in the slimy, slippery substance known as mucus.
- What are the signs and symptoms of mucinous carcinoma? Like other types of breast cancer, mucinous breast carcinoma may not cause any symptoms at first. Over time, a lump may grow large enough to be felt during breast self-examination or examination by a doctor.
- How big is mucinous carcinoma? The average mucinous carcinoma is about 3 cm, although they can be either smaller or larger than that.
- How is mucinous carcinoma diagnosed? It involves a combination of steps. These include physical examination of the breasts, a mammogram, ultrasound, MRI, and biopsy. Now or after surgery, the tissue should be tested for some other important features of a pure mucinous breast carcinoma. These include hormone receptor positive status, and HER2 negative status.
- What is the treatment for mucinous carcinoma? You and your doctor will work together analyse ways to develop your treatment plan for mucinous carcinoma of the breast. Treatment plans may include surgery to remove the cancer and in some cases any affected lymph nodes (lumpectomy, total or simple mastectomy), and adjuvant therapy (radiation therapy, hormonal therapy, or chemotherapy)
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