Breast Apocrine Metaplasia
Apocrine Metaplasia is a particular kind of changes in the cells and is associated with a variety of cystic breast disorders. So … the good news is … that apocrine metaplasia is a completely benign condition.
Furthermore, this condition, in itself, does not increase the risk for breast cancer. Medics sometimes describe apocrine metaplasia as a ‘benign epithelial alteration’ of breast tissue, which means that epithelial cells are undergoing an unexpected change.
These breast changes may show on a mammogram and biopsy as a mass or benign lesion, or possibly even develop into a palpable mass.
However, because there are associations with similar cell changes to breast tissue in apocrine breast carcinoma, it is quite important to investigate the situation thoroughly to confirm the benign differential diagnosis of apocrine metaplasia.
There are no clear mammographic distinctions for apocrine metaplasia. So, most likely follow up is with an ultrasound to confirm or a small biopsy.
What exactly is breast apocrine metaplasia?
Apocrine metaplasia is a ‘non-proliferative‘ breast lesion. Indeed, these changes are usually associated with breast fibrocystic change.
So, to recap, the term “proliferative” means that the cells are growing and growing and in a somewhat unpredictable way. Medics usually associate proliferative cell growth with carcinoma. But apocrine metaplasia is ‘non-proliferative’.
So, this means there will be new cell growth and change, but only in a limited and predictable way. In fact, “metaplasia”, (from the Greek word ‘meta’, meaning ‘change in form’) implies a reversible replacement of one type of cell with another type of cell.
Usually this is the result of some kind of irritation. So, after the discovery and treatment of the cause of the irritation the cells should return to normal.
In most cases the source of ‘stress’ which is causing the apocrine metaplasia is the development of a breast cyst. Indeed, the cause of breast cysts is any number of normal biological processes and obstructions in the breast.
Medics believe that apocrine-like cells form in the lining of developing microcysts due to the increase in intraluminal pressure because of secretions.
Why the name “Apocrine” Metaplasia?
Interestingly, the name can be a bit misleading. Apocrine metaplasia does not in fact have anything to do with ‘apocrine glands’. These glands affect sexual function, odor and sweat secretion. By extension, apocrine metaplasia is also unrelated to apocrine breast carcinoma, which can develop within the apocrine glands of the breast.
Instead, Apocrine metaplasia gets it’s name from the shape of the new cells, which have a visual resemblance (apocrine features) to apocrine glandular cells.
Specifically, the cells tend to show an accumulation of ‘secretory granules’ (small proteins) in the apical cytoplasm (the top layer of the ‘filler fluids’ of the overall tissue formation.)
Apocrine metaplasia arises in the TDLUs
So, specialists believe that apocrine metaplasia arises from the lobular cells located in the terminal ductal-lobular units (TDLU) of the breast. This is the final junction where milk from the lobules enters the breast ducts. Usually, these metaplasic cells will show up in the epithelial lining ( the wall ) of breast cysts that are either developing or already exist.
How do Doctors detect Apocrine Metaplasia of the breast?
Apocrine metaplasia is a cellular transformation that begins very early on in the development of a cyst. For this reason, it presents with a certain amount of ambiguity and may cause anxiety for the patient.
Usually a breast cyst will primarily contain fluids (unlike breast cancer), and perhaps a scattering of mineral deposits and calcifications.
A fully developed breast cyst will tend to have rather obvious and clinically apparent symptoms. Ultrasounds are also very useful in distinguishing benign breast cysts from a more ‘solid’ breast cancer.
But, in the very early stages of cyst development these mature features will not be apparent.
It is difficult to rule out breast cancer from X-rays of apocrine metaplasia
So, what usually happens is a women goes in for a routine screening mammogram and a strange pseudo-mass or lesion shows on the X-ray.
From the X-ray, the radiologist will note the development of unexpected features and cellular change. However, the radiologist will be unable to distinguish the benign nature of apocrine metaplasia from the more worrisome features of breast carcinoma.
The main issue regarding apocrine metaplasia is that, due to the immature nature of a breast cyst which is developing, follow-up evaluations are called for as a differential diagnosis from breast cancer, and this can cause anxiety.
A small biopsy is usually necessary for Apocrine Metaplasia of the breast
A mammogram of apocrine metaplasia will typically reveal an equal density mass, in a lobular shape and possibly with microlobulated margins.
There may also be groups or clusters of heterogeneous calcifications. Depending on the age of the lesion, ultrasound may not be able to detect any other relevant characteristics.
The consensus opinion among screening physicians is therefore that a needle biopsy is necessary.
In the ultrasound image above, the darker area is a “hypoechoic nodule with margins that are not smooth enough to call benign”. So, in this case, a biopsy was necessary and the result was a benign apocrine metaplasia.
The HER-2 protein is normally not present in apocrine metaplasia
A topic of current breast cancer research resolves around other ways of distinguishing apocrine metaplasia from breast carcinoma, without the inconvenience and expense of a core biopsy.
Among the ideas that scientists are playing with is the notion that the HER-2 protein, (human epidermal growth factor receptor 2) is associated with cell membranes and adhesion.
However, breast cancers commonly over express HER-2 protein but HER-2 is not present in apocrine metaplasia.
Older post-menopausal women are most likely to have Apocrine Metaplasia
Microscopic apocrine metaplasia is not uncommon in women in their 30’s. However, generally speaking, the condition is associated with older, post-menopausal women. It is most common in women in their 50’s.
But by the time women reach their 80’s and 90’s, about 50% will have apocrine metaplasia.
Conclusions regarding apocrine metaplasia and breast cancer
Speialists class Apocrine metaplasia in the’benign lesions’ category and it is usually associated with breast fibrocystic disease.
Furthermore, apocrine metaplasia can also be associated with other benign breast irritations like:-
but, it is also a condition that may develop alongside ‘solid lesions’ such as breast cancer. This is why it has to be taken seriously and medics investigate fully.
As to the question of an increase in the risk of breast cancer, only in ‘atypical’ or ‘complex’ apocrine metaplasia. This is whereby the apocrine metaplasia (non-proliferative) is accompanied by proliferative cellular growth (hyperplasia). Indeed, doctors do consider this case scenario as increase in the risk factor.
(And this is due to the hyperplasia, not the metaplasia) Otherwise, any increase in risk is only be the same; very low risk elevation common for all women who show a genetic predisposition for fibrocystic breast disease.
Q and A time
What is apocrine metaplasia?
It is a bit like a sweaty, dandruffy guy amongst a big group of normal, handsome men.
What are the cells like?
The cells are feeling a little awkward, like a certain relative you know but these are not cancer cells or malignant cells.
What if there is duct ectasia or adenosis or columnar cell change or atypia?
Pathologists can outline lots of descriptive words onto their reports, like saying the girl has short, red hair and freckles and dimples and long eyelashes. All these words still mean it is not cancer and it does not increase breast cancer risk.
What is papillary apocrine metaplasia? and what are apocrine metaplastic cells?
Papillary is a word meaning that under the microscope, the cells are forming together into finger-like shapes. Whether papillary or not, it doesn’t change things. The word metaplastic means that the cells are abnormal looking in some way, but it is not a carcinoma in situ.
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