-Micropapillary breast carcinoma (or invasive micropapillary
carcinoma IMPC) is a type of otherwise 'typical' invasive ductal carcinoma
which exhibits a unique and characteristic growth pattern.
-Skin invovlement (skin retraction) is another occassional feature of
invasive micropapillary carcinoma of the breast, and is observed in about
20-23% of all cases.
Histological
aspects of invasive micropapillary carcinoma of the breast
Histologically, invasive micropapillary breast carcinoma is
characterized by:
-Clusters of cohesive tumor cells within quite prominent
'clear spaces', which resemble dilated angiolymphatic vessels.
-The nuclei of tumor cells around the periphery can often
bulge with a kind of 'knobby' appearance.
- It is also quite common to see lymphatic involvement with
invasive micropapillary breast cancers.
The aggressiveness of invasive micropapillary carcinoma
may be related to the inverse polarity of the tumor cell clusters and
lymphotropism
-Invasive micropapillary breast carcinoma tumors will often
show lymphocytic infiltration.
-They tend to accumlate in the breast stroma, often forming
a lymphoid follicle. The presence of lymphocytes within the tumor will tend to
suggest a more aggressive cancer; more likely to metastize to the lymph nodes.
-Invasive micropapillary breast cancer is also characterized
histologically by an 'inverse polarity' of the tumor cell clusters. To clarify,
within the breast the 'functional unit' of the breast duct wall is a 'polar'
double-layered tube consisting of luminal epithelial cells surrounded by
myoepithelial cells and a basement membrane. In other words, there is an order;
an asymmetrical organization from 'outer to inner', and without this polarity,
the breast ducts would not able to properly excrete and transport breast milk.
But with micropapillary breast carcinoma (and some other breast cancers) this
polarity is reversed. The clusters of malignant cells which formed have the myoepithelial
cells outside of the epithelial-derived cells, with the basal layer exposed.
Hormone receptor status is high for micropapillary breast
cancer, somewhat against the norm
-Breast cancers which have higher positive rates for various
hormone receptors are usually considered 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 may be anticipated in approximately 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.
Factors most likely to affect 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. -The factors which seem most likely to
affect a poor prognosis are skin involvement, and nodal status.
-However, once lymph node metastasis is confirmed, the
outlook for invasive micropapillary breast cancer does not differ significantly
from other breast cancers which have metastized to the lymph nodes.
-Skin invasion is a signficant predictor of a poor prognosis
with invasive micropapillary breast cancer, leading 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, and lymphatic vessel
density.
Treatment for invasive micropapillary carcinoma of the
breast
-Invasive micropapillary breast carcinoma is a highly
aggressive from of breast cancer which requires the earliest possible diagnosis
and aggressive intervention and management.
-The high rate of local recurrence and high probability of
lymph node metastasis will usually prompt the surgeon to suggest either a
modified or full radical mastectomy, though breast conserving surgery is
attempted in a minority of situations.
- Axillary dissection will usually accompany a modified or
radical mastectomy.
-Adjuvant treatment with chemotherapy is often utilized as
well, but usually only if there is evidence of axillary node metastasis, or
when there is not yet lymph node metastasis but the tumor is larger than 1 cm.
