A Complex Cyst of the Breast - Moose and Doc (2023)

A ‘complex‘ or ‘complicated‘ breast cyst, refers to cysts that contain something besides clear fluid. A simple breast cyst, on the other hand, only contains clear fluid. Indeed, this is usually something harmless like an old blood clot or debris.

These cysts are on the upper end of the continuum of abnormalities that can sometimes happen to breast cysts. Simple breast cysts are fluid filled, and with a uniformly thin and smooth wall to their oval shape. A complex breast cyst, however, contains a good percentage of solid elements suspended within the fluid, and may also feature segmentation (septation) and some regions of the cyst wall that are ‘thicker‘ than others.

A Complex Cyst of the Breast - Moose and Doc (1) A Complex Cyst of the Breast - Moose and Doc (2)

Simple cysts are supposed to have thin walls and contain only clear fluid.

Complex breast cysts account for approximately 5% of breast cysts that are present on screening mammograms. So, usually a complex cyst of the breast indicates close follow-up and sometimes a biopsy.

There is a very very small chance that a complex breast cyst could be associated with malignant breast cancer, so they merit a higher degree of scrutiny.

A Complex Cyst of the Breast - Moose and Doc (3)

A Complex Cyst of the Breast - Moose and Doc (4) A Complex Cyst of the Breast - Moose and Doc (5)

One look at this, and I know it’s not cancer.

Ultrasound features of a Complex Cyst of the Breast

There are no standard definitions or signature features of a complex cyst. Indeed, these types of cysts are a heterogeneous (or varied) group of lesions with different presentations.

On ultrasound, radiographers will typically evaluate a complex breast cyst in terms of the following features:-

  • Internal echoes
  • The presence or absence of posterior enhancement (evidence of an intracystic mass)
  • Thin septations
  • A thickened and/or irregular wall (lobulations).

So, the results of the ultrasound can influence the strategy for follow-up evaluation or treatment.

The radiologist will be looking for…

Findings of septations (thin walls that divide the cysts into segments) are really of little concern. What the radiologist is looking for is hard evidence of an intracystic mass, which would be indicative of neoplastic cell growth, and that would probably lead to histological evaluation. Even so, the chances of the neoplasm being breast cancer are very low.

A Complex Cyst of the Breast - Moose and Doc (6) A Complex Cyst of the Breast - Moose and Doc (7)

If a breast cyst contains a septation, it’s not a cancer. Cancers grow into round shapes, not slender dividing-walls between fluid.

The decision to biopsy a complex cyst remains subjective

Findings of internal echoes without a distinctly visible solid mass or, alternatively, an ‘anechoic’ lesion with no posterior-wall enhancement would be a bit of a judgement call.

It likely means that various particles are floating in the cystic fluid and, and the complex cyst is extremely likely to be completely benign. ( It could be floating cholesterol crystals, blood, pus, or milk of calcium crystals.) The decision to biopsy, or aspirate, or simply follow up with observation, would be somewhat subjective in this instance.

Higher risk of malignant association when there are irregular lobule shapes in the margin

The presentation of complex cysts and actual malignancy development, when it rarely occurs, can be a little bit irrational. The presence of an intracystic mass (probable neoplasm) does not statistically correlate with a higher risk of malignancy.

But a thick cystic wall, lobulation (irregular lobule shapes in the wall), and hyperechogenecity (many internal echoes), particularly when occurring in combination, may carry a higher risk of an underlying malignancy.

A Complex Cyst of the Breast - Moose and Doc (8)

Above is a picture of a complex cyst on a mammogram. To the radiologist, it could be anything, solid or a liquid cyst, so it would need an ultrasound.

Rate or risk of malignancy associated with complex breast cysts

The vast majority of complex breast cysts turn out to be benign. As for those that eventually show as developing due to malignant breast cancer, there is quite a range of opinion as to the ‘malignancy rate’.

This is probably due to the fact that there is no consistent definition of a complex cyst. Some studies place the rate as high as 63%, others as low as 0.3 %. So, the best answer is, ‘what does the histological evaluation say”.

The ultrasound confirmation of a complex cyst of the breast can not be generalized as having any particular or consistent rate of association with breast cancer.

Of interest, a personal or family history of breast cancer, and menopausal status appear to have no bearing on the development of a malignant neoplasm.

Biochemically distinct types of breast cysts?

One of the trends in cancer research is to look for different biochemical profiles, or ‘markers’ which tend to be associated with particular types of breast cancers or benign lesions.

Different cells may release different proteins and other chemicals, and that can give clues as to various cell growths and patterns that may be developing.

With breast cysts, there does appear to be a tendency towards two basic ‘lining patterns’. Firstly, those lined with apocrine epithelium and secondly, those lined with flat epithelium. (Apocrine epithelial cells are basically secretion cells, while ‘flat epithelium’ refers to a flat or columnar ‘stacking pattern’ or layering of normal epithelial cells.)

The different cyst-lining cell patterns can also be measured biochemically using [Na+]/[K+], ( the ‘sodium to potassium ratio’ ) of the cystic fluid. There is some suggestion that cysts with ‘low electrolyte’ readings ( higher potassium and less sodium) may indicate a higher risk for breast cancer involvement, but this is purely speculative at this time.

If the ‘wall’ of a complex cystic breast mass is getting thicker, there may be additional issues.

In summary, this ‘biochemical-analysis’ approach for evaluating breast cysts suggests that where the epithelial wall is ‘getting thicker‘ by adding certain types of cells, the risk of malignant association may be higher.

The lobulated cyst

The word lobulated, refers to the surface of something that is fairly rounded. A peach is an example of a surface that isn’t perfectly spherical. A peach has a cleft causing an indentation in the surface. That cleft in the surface makes the peach a little “lobulated” on that part of the surface. Cysts can be like that peach, and might show an outward bulge, or an inward indentation on part of its surface.

I don’t personally use the word lobulated for cysts. This is because it causes people to search for the meaning of the word and become anxious for no good reason.

A lobulated cyst, refers only to the surface of it and is just a cyst. On the other hand, a lobulated solid nodule has a different significance altogether.

A solid nodule that bulges in a way that is not a perfect sphere, can indicate that some internal parts of the nodule are growing faster than other parts, which is a mild clue the solid nodule might be cancer.

But since a cyst has nothing growing inside it, the lobulated cyst surface is caused from outside of the cyst. Probably, the cyst is simply lying against a fibrous band or blood vessel that doesn’t stretch as easily as everything else around the cyst. So, I hope you relax about the lobulated cyst.

Shall we Q and A together?

What is complicated about a complex cyst of the breast?

Nobody knows how cysts can get blood or grunge in them, or fibrin balls that look like internal nodules. So, this is why they are classed as ‘complicated’.

Should it be removed?

What is the treatment of a complicated breast cyst? In general do not remove it. A radiologist may aspirate a complex cyst if it is big enough to hurt.

What are the symptoms of a complex cyst and why?

A complex cyst of the breast can hurt because it has expanded into surrounding tissue. So, the surrounding tissue says, ‘who invited you, quit crowding me, you’re so pushy’. Next, the nerve endings for pain sensation start sending signals of pain to your brain.

What percentage of complex cysts are cancerous?

Not exactly Zero, but very closein fact, according to medical studies around 0.4%.

Where do complex cysts grow and form?

Anywhere in the fibro-glandular cone of breast tissue, but not in the pure fat. Short-answer, almost anywhere.

What color is breast cyst fluid?

Normally clear yellow, or resembling tea color or beer color. The color might have a slight tinge of red. A complex cyst may have some extra colors, such as a little cloudy grey or green in the fluid. If you looked at the fluid in a glass vial, you might see speckled debris floating.

When to aspirate or remove the cyst?

If the radiologist recommends it, go ahead and aspirate. Or, if the cyst hurts you, YOU can ask for it to be drained or removed. Aspiration is easier.

Why do cysts grow? Can cysts burst or rupture?

Cysts do not usually burst or rupture unless someone punches really hard at them. They grow to the size where surrounding pressure stops them and then they stop growing.

Further Reading

  • What is a Breast Cyst
  • Clusters of Breast Microcysts
  • Index of ALL our Benign Breast Conditions
  • Fibrocystic Breast Disease
  • Epidermoid Breast Cyst

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