Case: A 37 year old woman notices a palpable density in one breast on self-exam.
The region is not tender, and there is no inflammation or discharge.
She is anxious that this might be cancer.
A core biopsy is obtained. Can you describe what you see?
Within a large dilated duct sits a structure folded into papillary fronds lined by a
basophilic epithelium surrounding a pink central fibrovascular stroma.
The area in the box is magnified below.
Compare the papillary surface epithelium to the surface of the duct wall.
Both seem to be composed of similar cells, forming a simple layer resting upon a
basement membrane. The latter is not easy to see directly but can be visually
enhanced with special stains. Both tissues have matured in the manner
characteristic for ductal tissue, with a polarized surface facing the duct lumen.
Each image below shows a single layer of epithelial cells, resting on a basement
membrane. The epithelial cells are “polarized” since they have distinct basal and
apical surfaces.
The cyst wall (from another case) shows epithelial cells with abundant cytoplasm
and specialized secretory structures at the apical surface. To a lesser degree, the
epithelial cells of both the duct wall and papilloma also differ between the basal
surface and the apical surface. Deep to the epithelial layer are myoepithelial cells
associated with the fibrovascular layer. However, and important to the definition of
“Benign”, the epithelial cells never penetrate across the basement membrane.
The structure is named an Intraductal Papilloma.
What does the name tell you?
This is a benign proliferation in a duct. If the lesion had been malignant, the name
would have included the word carcinoma, that is intraductal carcinoma. The most
important observation is that there is no evidence of invasion, a feature of
malignancy. In other words, the epithelium does not penetrate the basement
membrane and spread into adjacent areas. Many terms have been used historically
to describe altered growth. Neoplasia refers to a spontaneous proliferation that
increases cell number. Dysplasia refers to a process that interferes with normal
differentiation. Ongoing genomic studies now associate both with mutations in the
involved tissue. Currently, the term dysplasia also implies a lesion that has
increased potential to undergo further change in a progression toward malignancy.
All these terms are changing in usage as our understanding migrates from
phenotypic appearance under the microscope to genotypic understanding that may
be unique to each lesion. The proliferative lesion shown in this case does not show
atypical cellular maturation, and is currently considered of little additional risk for
malignancy. It is more worrisome if there is atypical piling up of the epithelial cells
on each other (not seen here). When seen, such atypia raises the likelihood of future
cancer in the breast. In summary, this lesion, an intraductal papilloma, is benign and
does not need further treatment. However, the patient should remain alert for
changes in the future.