Breast Apocrine Metaplasia

Apocrine Metaplasia refers to a particular type of cell change. This is a type of ‘umbrella term’ that relates to 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 of breast cancer. Medics sometimes describe apocrine metaplasia as a ‘benign epithelial alteration’ of breast tissue. This means that the 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.

The word apocrine means related to sweat glands, but this is only a resemblance. Apocrine metaplasia is not actually sweat gland related.

So, not really Skin-related? Internal breast cells that start to resemble skin cells?

Metaplasia simply means change, like cheese getting hard if it is out of the fridge.

However, there are similar cell changes in breast tissue to that which occur in apocrine breast carcinoma. Therefore, it is important for medics to investigate the situation thoroughly to confirm a benign differential diagnosis of apocrine metaplasia.

There are no clear mammographic distinctions for apocrine metaplasia. So, the most likely follow-up is with an ultrasound, or a small biopsy, to confirm.

But if my biopsy already shows apocrine metaplasia, I can relax, right?

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, odour and sweat secretion.

In addition, apocrine metaplasia is also unrelated to apocrine breast carcinoma, which does develop within the apocrine glands of the breast.

Instead, the name apocrine metaplasia derives from the shape of the new cells. These cells 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.)

Good to know, that it does not turn into cancer.

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 metaplastic 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 contain mainly 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. Thus, 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 on X-ray

So, what usually happens is a woman 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 cancer.

Due to the immature nature of a developing breast cyst, follow-up evaluations are necessary to rule out breast cancer. Often these tests and callbacks can cause anxiety for the patient.

If I saw the picture below on ultrasound, I would not know exactly what it was. So, I would biopsy it.

And when the biopsy result shows it is benign, then everyone can relax.

A small biopsy is usually necessary

A mammogram will typically reveal an equal density mass, in a lobular shape, 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 benign apocrine metaplasia.

The HER-2 protein is normally not present

One aim of the current breast cancer research is to find a way to distinguish between breast cancer and apocrine metaplasia without using a core biopsy.

A core biopsy is an invasive procedure and may cause the patient unnecessary anxiety and discomfort. Furthermore, it is an unnecessary expense.

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 overexpress 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 occurs more often in older, post-menopausal women. Indeed, 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

Specialists class this condition as apocrine metaplasia in the ‘benign lesions’ category and it is usually associated with breast fibrocystic disease.

in the ‘benign lesions’ category and it is usually associated with breast fibrocystic disease.

Furthermore, medics may use this term in association with other benign breast irritations like:-

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 increasing the risk factor for breast cancer.

(And this is due to the hyperplasia, not the metaplasia) Otherwise, any increase in risk is only 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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