Immunohistochemistry in Breast Pathology - Part 1
Resolving common diagnostic dilemmas
- Benign/malignant e.g. Radial scar v Invasive cancer; Nipple adenoma - See also Sclerosing Lesions
- Epithelial proliferations e.g. UEH v ADH v DCIS - See also Carcinoma in situ and ADH & ALH
- In situ v microinvasion
Benign v Malignant
Myoepithelial markers are employed very frequently to help differentiate invasive from non-invasive lesions,
particularly Radial Scar v Grade 1 invasive cancer; intraduct papilloma v Papillary intraduct carcinoma and ADH v DCIS.
In benign sclerosing lesions the myoepithelial layer is retained around glandular structures
and therefore these can be expected to show positive staining with a marker such as CK 5/6 or CK14. In low grade invasive carcinomas the
myoepithelial layer is absent and CK 5/6 staining is negative.
The following images illustrate the use of IHC in these conditions:
Low power view of radial scar
Detail of central fibroelastotic scar with entrapped glands
Low power view of core biopsy showing sclerosing adenosis and adjacent invasive carcinoma.
'Mouse over' - Green circle = sclerosing adenosis; yellow ellipse = area of invasive carcinoma
Detail of above image
'Mouse over' - Area (A) = sclerosing adenosis; Area (B) = invasive carcinoma
Positive CK 5/6 staining of sclerosing adenosis area (A) and negative staining in invasive area (B)
Low grade invasive carcinomas v benign tubular pattern proliferations
In the following example the H&E appearances are strongly indicative of the diagnosis of Tubular Carcinoma. Immunostaining for myoepithelial markers
shows an intact myoepithelial layer on the right hand side of the picture marking an intact duct with negative staining of the tubular (carcinoma) area.
As a practice point it is very reassuring to have a focus of positive staining in a section where the answer to
the problem is being given by negative staining thus proving that the stain has worked and is not simply
a technical failure (false negative).
Grade 1 invasive carcinoma - this is a tubular carcinoma to illustrate the difference from a radial scar
For a further example of use of immunohistochemistry in this diagnostic area click here:
Nipple adenoma is a benign glandular proliferation presenting as a nodule beneath the nipple. On core biopsy its overall benign architecture
can be difficult to appreciate and immunohistochemistry is very helpful in confirming the
presence of an intact myoepithelial layer throughout the lesion.
In the example of an excised lesion below CK 5/6 shows rather weak and patchy staining however P63 is totally convincing.
Low power view of nipple adenoma
'Mouse over' for medium power image - a dual cell population can be appreciated at this power
CK 5/6 staining confirms the presence of an intact myoepithelial layer - it is weak in areas
'Mouse over' for P63 stain
For further immuno images from this lesion click here:
For a further example of this entity click here:
Papillary lesions, ADH & DCIS
Differentiating intraduct papillomas from papillary carcinoma can be difficult. In addition to architectural and cytological characteristics of these two lesions
(see also section on papillary lesions) benign papillary lesions are characterised by the retention of a myepithelial population often throughout the lesion. The following
sequence of images illustrate this point.
In the papilloma images the immunostain 'P63' has been used - this stains nuclei
of myoepithelial cells. In the papillary carcinoma ck 5/6 has been used which stains the cytoplasm of myoepithelial cells.