Definition/General
Introduction:
Epithelial hyperplasia of the breast, also known as usual ductal hyperplasia (UDH) or epitheliosis, is a benign proliferative lesion characterized by an increased number of epithelial cells within the ducts and lobules
It is a very common finding.
Origin:
It arises from the terminal duct-lobular unit (TDLU).
Classification:
It is classified as a proliferative breast lesion without atypia.
Epidemiology:
It is extremely common and is often an incidental finding in breast biopsies.
Clinical Features
Presentation:
It is an incidental microscopic finding.
Symptoms:
Asymptomatic.
Risk Factors:
There are no well-established risk factors.
Screening:
It can be associated with microcalcifications on mammography.
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Gross Description
Appearance:
There are no specific gross findings.
Characteristics:
Gross findings are not specific for this microscopic diagnosis.
Size Location:
Gross findings are not specific for this microscopic diagnosis.
Multifocality:
Often multifocal.
Microscopic Description
Histological Features:
The ducts and lobules are filled with a proliferation of a mixed population of epithelial and myoepithelial cells
The cells are arranged in a haphazard or streaming pattern, with irregular, slit-like secondary lumens.
Cellular Characteristics:
The cells are heterogeneous, with variable sizes and shapes
The nuclei are oval to spindle-shaped, with fine chromatin and inconspicuous nucleoli
There is nuclear overlapping.
Architectural Patterns:
Streaming, swirling, and bridging of cells are characteristic.
Grading Criteria:
This is a benign lesion.
Immunohistochemistry
Positive Markers:
UDH shows a mosaic or mixed pattern of staining for cytokeratins, including high molecular weight cytokeratins like CK5/6
ER staining is typically weak and heterogeneous.
Negative Markers:
Not typically required for diagnosis.
Diagnostic Utility:
IHC for CK5/6 is very useful to differentiate UDH from atypical ductal hyperplasia (ADH) and low-grade DCIS.
Molecular Subtypes:
Molecular subtyping is not relevant for this benign condition.
Molecular/Genetic
Genetic Mutations:
UDH is a polyclonal proliferation.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
UDH is associated with a small increased risk (about 1.5-2 fold) of developing invasive breast cancer.
Therapeutic Targets:
No treatment is required.
Differential Diagnosis
Similar Entities:
Atypical ductal hyperplasia (ADH)
Low-grade DCIS.
Distinguishing Features:
ADH and low-grade DCIS are composed of a monotonous population of cells, form rigid, geometric spaces, and are negative for CK5/6.
Diagnostic Challenges:
The main challenge is distinguishing florid UDH from ADH or low-grade DCIS.
Rare Variants:
There are no specific rare variants.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[specimen type], measuring [size] cm in greatest dimension
Diagnosis
[diagnosis name]
Classification
Classification: [classification system] [grade/type]
Histological Features
Shows [architectural pattern] with [nuclear features] and [mitotic activity]
Size and Extent
Size: [X] cm, extent: [local/regional/metastatic]
Margins
Margins are [involved/uninvolved] with closest margin [X] mm
Lymphovascular Invasion
Lymphovascular invasion: [present/absent]
Lymph Node Status
Lymph nodes: [X] positive out of [X] examined
Special Studies
IHC: [marker]: [result]
Molecular: [test]: [result]
[other study]: [result]
Final Diagnosis
Final diagnosis: [complete diagnosis]