Adnexal carcinoma is a kind of cancer that either arises from or resembles the sweat or sebacious glands. Microcystic adnexal carcinoma is a rare malignant tumor which is essentially of sweat gland origin. It is a slowly progressing tumor, which is mostly associated with the skin, and not the breast duct tissues. However, as there are some of the adnexal glands in the breast, microcystic adnexal carcinoma has been known to occur in the breast. However, it is not really considered a kind of 'breast cancer' per se, but rather a skin cancer which has either grown in the skin of the breast, or metastized to the region. However, a woman undergoing a clinical evaluation of an unusual lesion or 'lump' on her breast and concerned about potential breast cancer may discover that the lesion is in fact a microcystic adnexal carcinoma.
Adnexal carcinoma of the breast (which is really a skin cancer growing on the breast) is often misdiagnosed in both the clinical and histological settings. Clinically it usually presents as a firm subcutaneous nodule, which is often pale yellow and with overlying telangiectasias (dilated superficial blood vessels, appearing as 'red spots'). Most commonly, adnexal carinoma occurs in the face, head, and neck, but rarely it does occur on the breast. An adnexal carcinoma of the breast might also present as a cyst, and frequently can be present for many years before being screened as a potential breast cancer. Adnexal carcinomas are usually without symptoms, and that is why they tend to be ignored. Occassionaly, they may create symptoms of numbness and burning, even paresthesia, but not very often. They are generally considered a benign caricinoma, but there is a small possibility of malignancy and lymph node metastasis.
There are various subtypes of adenxal carcinomas which may occur on the breast. A trichoepithelioma is a benign epithelial tumor which developes from the hair follicles. Some people consider a trichoepithelioma to be a poorly differentiated hamartoma of the hair germ. These lesions are most common on the face, naturally, but could develop on the breast. A syringoma is another harmless sweat duct tumor, which is usually found on the eyelids. However, they can occur on the breast. Syringomas are usually either yellow or skin-colored firm rounded bumps, and very small, only 1-3 mm in diameter. Hidradenocarcinoma is another kind of adnexal carcinoma which is derived from the epithelial cells of sweat glands. The term is sometimes also used in a general sense to describe all skin tumors which have a resemblance to the epithelial elements of sweat glands.
Infiltrating syringomatous adenoma (ISA) of the breast is another term that is often used interchangeably with microcystic adnexal carcinoma. Sometimes the lesion is also referred to as a well-differentiated adenosquamous carcinoma, or simply as a sclerosing sweat duct. Microcystic adnexal breast carcinomas, or infiltrating syringmatous adenomas of the breast can often be confused with a
well-differentiated tubular carcinoma of the breast. Both kinds of tumors have a pattern of infiltration which tends to invade the surrounding nerves and smooth muscle tissue. However, the presence of aquamous metaplasia in the adnexal breast carcinoma will differentiate it from a tubular breast carcinoma.
Adnexal carcinomas are quite frequently associated with a cancer metastasis to the ovaries. It is estimated that about 35% of ovarian metastasis of carcinoma are from from breast cancers. In some studies, the figure is a bit higher, suggesting that about 50% of ovarian cancers are due to breast cancer metastasis. However, not all neoplastic growth in the ovaries are malignant carcinoma. About 75% of lesions which develop in the ovaries in women who have breast cancer turn out to be benign adnexal masses. So, overall, the rate of metastasis of carcinoma which actually develops in the ovaries from breast cancer is very small, and is a reflection of an advanced progression of the breast cancer.
The average interval between the diagnosis of breast cancer and a metastasis to ovarian carcinoma is just under one year, and the average survival time once ovarian metastasis has occurred is estimated at about 16 months. However, it must be remembered that metastasis of breast cancer to the ovaries is still very unlikely, and it is far more likely that a neoplastic grows in the ovaries will turn out to be a benign adnexal tumor.
If a microcystic adnexal carcinoma develops in the breast, it will likely appear mammographically as an ill-defined spiculated mass, perhaps with some smudgy areas of infiltration. However, there are no specific radiological features of an adnexal breast carcinonoma/infiltrating syringomatous adenoma which would distinguish it from conventional breast carcinoma. The actual location of the tumor, however, might be a clue. Microcystic adnexal carcinomas occur in the skin of the breast and as such will tend to be towards the peripheries.
Microscopically, a microcystic adnexal breast carcinoma will likely feature a stratified proliferation of microcysts, cords, and ducts of cells showing squamous or adnexal differentiation. The tumor will often extend beyond the clinical margins with local spreading in the dermal, subcutaneous, and perineural tissues (into the underlying muscle). Histologically, a microcystic adnexal breast carcinoma may exhibit both pilar and sweat duct differentiation, with a stroma of dense collagen. If a glandular component is particularly prominent, the tumor might be classified as a sclerosing sweat duct carcinoma or possibly a malignant syringoma. Of note, cellular atypia, mitoses, and also necrosis, are amost completely absent from breast adnexal carcinomas.
Frequently, the 'deeper' component of a microcystic adnexal breast carcinoma will have a schirrous appearance which shows small nests and strands of cells within a dense, hyalinized stroma. Epithelial elements are often somewhat diminished in number, to small clusters of just 2 or 3 cells. Cytologically, the tumor cells are usually of a uniform size. And, characterisitcally, an adnexal breast tumor will usually exhibit keratin-filled cysts, and nests and cords of 'basaloid' cells, which may invade deep into the dermis to the subcutaneous fat.
The histological evaluation is an important part of the differential diagnosis, which might consider alternative diagnoses of adenosquamous carcinoma, squamous cell carcinoma, morpheaform basal cell carcinoma, and possibly metastatic breast carcinoma. Immunohistochemically, the tumour cells also tend to stain positive for EMA and various cytokeratins (especially CK7). Microcystic adnexal carcinomas have been shown to commonly express p63, usually in more than 75% of the cells. S-100 positive cells are also frequently present, but the stroma will tend to be CD34 negative.The luminal cells of a microcystic adnexal breast carcinoma will typically express CEA. A low level of Ki 67 in an adnexal breast carcinoma would typically indicate a low proliferative index.
Microcystic adnexal breast carinomas are essentially a form of skin carcinoma, which can occur in the breast. It is considered to be a benign form of carinoma, but is treated with a wide surigical excision because of its 'locally agressive' behaviour. In other words, it has a high rate of local recurrence, sometimes as high as 45%. It is a very slow growing tumor, but re-excision is still often required. Overall, the 10 year rate of recurrence for a microcystic carcinoma of the breast may be estimated at around 18%. Malignancy is rare in microcystic adnexal breast carcinomas. Once the tumor has been excised, routine follow up is mandatory, and a sentinel lymph node biopsy might be recommended. Generally speaking, the single most important prognostic factor for predicting breast cancer survival is the status of the lymph nodes. Routine staining of a tumor-site biopsy sample has only a 1% chance of finding a tiny focus of metastatic breast cancer smaller than 3 cell diameters, so, a sentinel node biopsy might be a prudent management approach. It is always a good idea to have any curious skin lesion or bump on the breast examined for potential breast cancer. Adnexal carcinoma is slow growing and benign and frequently ignored. The potential for malignancy is small, but better to have it checked and removed just to be sure.
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