Micropapillary Breast Cancer

Micropapillary breast cancer (or invasive micropapillary carcinoma IMPC) is a type of otherwise ‘typical‘ invasive ductal carcinoma which exhibits a unique and characteristic growth pattern.

This type of breast cancer is quite rare. Only 6% of breast cancer cases are micropapillary.

The tumor, in this type of breast cance develops fairly prominent clear spaces, into which the tumor cells form into cohesive clusters.

Presentation of Micropapillary Breast Cancer

Unfortunately, Invasive micropapillary breast cancer tends to be very aggressive with a very high rate of lymph node metastasis. Indeed, the rate of lymph node involvement is estimated at between 75% and 100%.

Skin involvement (skin retraction) is another occasional feature of invasive micropapillary carcinoma. Skin problems occur in around 20-23% of all cases.

The average age range for development of invasive micropapillary breast carcinoma is typically around the early 60s.

Usually, invasive micropapillary carcinoma presents as a palpable mass in over 90% of cases.

Interestingly, and, for no apparent reason, micropapillary breast cancer tends to affect the left breast more often than the right, about 65% of the time.

I just want to let you know that this website is a little bit old, from somewhere around the year 2000-ish. So we have created a brand new page on up-to-date information about Micropapillary Carcinoma.

Micropapillary Breast Cancer: Pure and Mixed

Specialists very rarely see a ‘pure‘ invasive micropapillary breast tumor. Usually, micropapillary breast carcinoma is mixed-in with invasive ductal carcinoma.

Breast cancer specialists call mixes of breast cancer ‘not otherwise specified’ or NOS.

The relative amount of the ‘micropapillary component‘ ranges from 20% to 80% of the total tumor mass. In the majority of cases, the micropapillary component is less than 25%. However, the relative amount of micropapillary features does not have a significant bearing on the behavior of the tumor.

Micropapillary breast cancer is of an ‘angioinvasive‘ phenotype. What does this mean? Well, the cancer has a tendency to develop and spread into blood-supply elements.

So, all breast cancers which have this predisposition tend to have higher rates of metastasis.

Histological aspects of invasive micropapillary carcinoma of the breast

On histology, clusters of cohesive tumor cells within quite prominent ‘clear spaces‘, resembling dilated angiolymphatic vessels characterise invasive micropapillary breast carcinoma.

The nuclei of the tumor cells around the periphery can often bulge with a kind of ‘knobby‘ appearance.

Sometimes, specialists refer to micropapillary breast tumors as ‘hedgehog‘ tumors because of this feature.

It is also quite common to see lymphatic involvement with invasive micropapillary breast cancers.

Why is Invasive Micropapillary Breast Cancer Aggressive?

These types of breast tumours often show lymphocytic infiltration. They tend to accumulate in the breast stroma, often forming a lymphoid follicle.

The presence of lymphocytes within the tumor will tend to suggest a more aggressive cancer. This means that the cancer is more likely to metastasize (or spread) to the lymph nodes.

On histology, an ‘inverse polarity‘ of the tumor cell clusters, often characterizes micropapillary breast cancer.

To clarify:-

Within the breast, the ‘functional unit‘ of the breast duct wall is a ‘polar‘ double-layered tube.
This tube consists of myoepithelial cells and a basement membrane that surrounds luminal epithelial cells
So, there is an order – an asymmetrical organization from ‘outer to inner‘. Without this polarity, the breast ducts would not be able to properly excrete and transport breast milk.

So with micropapillary breast cancer (and some other breast cancers), this polarity is reversed. The clusters of malignant cells which form have the myoepithelial cells outside of the epithelial cells, with the basal layer exposed.

Hormone Receptor Status and Micropapillary Breast Cancer

Breast cancers which have higher positive rates for various hormone receptors tend to have a more positive outlook.

For one thing, they tend to be more responsive to chemotherapy.

With invasive micropapillary breast cancers, about 70% tend to be ER-positive and around 60% are positive for progesterone receptors. HER2 overexpression is present in about 40% of cases.

For most breast cancers this degree of positive hormone receptivity would be a hopeful indicator. In invasive micropapillary breast carcinoma, however, hormone receptor status appears to have no particular significance to the outlook.

Research also shows the expression of MUC1 in invasive micropapillary breast carcinoma, particularly in the stroma-facing surface of the cells clusters.

MUC1 is a glycoprotein which is typically expressed in the apical surface of normal epithelial cells. It is likely that MUC1 helps maintain the formation of the lumen. Furthermore, medics believe that the unexpected presence or secretion of this protein might be responsible for the ‘accentuated‘ outlines of the micropapillary cellular units.

In conventional breast carcinomas, MUC1 expression tends to be either apical, intracytoplasmic, or intercellular.

Mammographic features of invasive micropapillary breast carcinoma

At the present time, no specific mammographic, sonographic, or MR imaging characteristics have been identified for micropapillary breast carcinoma.

However, all imaging characteristics of micropapillary breast cancer are highly suggestive of malignancy.

Mammographic studies of invasive micropapillary carcinoma of the breast tend to show a high density, irregular or round solid mass. (Irregular shapes are somewhat more common).

Micropapillary breast carcinoma tumors tend to have spiculated margins, (between 50%-70% of the time). In addition, these types of tumors are variably associated with microcalcifications; these occur more or less 50% of the time.

Microcalcifications, when present, tend to be either pleomorphic, punctate, or both, and their distribution tends to be either segmental or clustered.

MRI may be a useful tool in diagnosing micropapillary breast cancer

MRI (magnetic resonance imaging) may or may not be useful in evaluating invasive micropapillary breast cancer tumors.

invasive-micropapillary-breast-carcinoma-mri

In addition, MRI can be a useful ‘preoperative‘ tool for defining the extent of the tumor and excluding the possibility of multifocality.

MRI imaging can also frequently show additional findings, such as, skin thickening, lymphadenopathy and chest wall invasion, which would not be apparent through other diagnostic modalities.

Ultrasound images of invasive micropapillary breast tumors will tend to show a solid hypoechoic mass, with either irregular or microlobulated margins.

Over 90% will tend to show a homogeneous echo texture, and around 60% may show posterior acoustic shadowing. The sonogram of invasive micropapillary breast carcinoma (see below) features a round, hypoechoic, solid mass (about 1 cm in diameter) with irregular margins and prominent posterior acoustic shadowing.

invasive-micropapillary-breast-carcinoma-ultrasound

Factors most likely to effect the prognosis of invasive micropapillary breast cancer

The mortality rate for micropapillary breast cancer is, unfortunately, quite high, at over 40%. The average interval between full presentation of the disease and death is about 3 years.

That’s really not good.

The factors which seem most likely to affect a poor prognosis are skin involvement, and nodal status.

However, if lymph node metastasis is present, the outlook for invasive micropapillary breast cancer does not differ significantly from other breast cancers which have metastasized to the lymph nodes.

Skin invasion is a significant predictor of poor prognosis with invasive micropapillary breast cancer. Indeed, skin involvement leads to mortality in about 50% of all cases in which it occurs.

Aspects of the tumor which are most likely to influence the risk of metastasis are:-

the histologic grade (based on the number of atypical cells and the rate of mitosis)
lymphocyte infiltration
lymphatic vessel density
Grade: Low or high grade also has an influence.

Treatment for invasive micropapillary carcinoma of the breast

Invasive micropapillary breast carcinoma is a highly aggressive form of breast cancer. Thus, micropapillary breast cancer requires the earliest possible diagnosis and aggressive intervention and management.

The high rate of local recurrence and a high probability of lymph node metastasis will usually prompt the surgeon to suggest either a modified or full radical mastectomy.

However, in a minority of cases, surgeons may attempt breast-conserving surgery. Axillary dissection will usually accompany a modified or radical mastectomy.

Your specialist may also recommend adjuvant treatment with chemotherapy. This will often be the case if there is evidence of axillary node metastasis or the tumor is larger than 1 cm.

What about micropapillary DCIS? Is this page about that?

Good question. No. This page is about the invasive cancer. The DCIS or ductal carcinoma in situ is a different thing.

References

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More References

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