Definition/General
Introduction:
A simple fibroadenoma is a fibroadenoma that does not contain any of the complex features (cysts >3mm, sclerosing adenosis, epithelial calcifications, or papillary apocrine change)
It is the most common type of fibroadenoma.
Origin:
It arises from the terminal duct-lobular unit (TDLU).
Classification:
It is a subtype of fibroadenoma.
Epidemiology:
They are most common in young women, with a peak incidence in the 20s and 30s.
Clinical Features
Presentation:
Presents as a painless, firm, mobile, well-circumscribed, rubbery mass.
Symptoms:
A painless, mobile lump is the most common symptom.
Risk Factors:
Hormonally responsive.
Screening:
On mammography, they appear as a well-circumscribed, oval mass
On ultrasound, they are a well-defined, hypoechoic mass.
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Gross Description
Appearance:
A well-circumscribed, encapsulated, firm, gray-white mass that bulges from the cut surface.
Characteristics:
The cut surface is whorled and may have slit-like spaces.
Size Location:
Size is variable, but they are typically 1-3 cm.
Multifocality:
Can be multiple and bilateral.
Microscopic Description
Histological Features:
A biphasic tumor with a proliferation of benign glands and stroma
The glands are lined by a double layer of epithelial and myoepithelial cells
The stroma is typically bland and fibroblastic
There are no complex features.
Cellular Characteristics:
The epithelial and stromal cells are benign, with no atypia or mitotic activity.
Architectural Patterns:
Can be intracanalicular, pericanalicular, or mixed.
Grading Criteria:
This is a benign lesion.
Immunohistochemistry
Positive Markers:
The IHC profile is similar to that of a conventional fibroadenoma.
Negative Markers:
Not applicable.
Diagnostic Utility:
IHC is not usually necessary for diagnosis.
Molecular Subtypes:
Not applicable.
Molecular/Genetic
Genetic Mutations:
Recurrent mutations in the MED12 gene are common.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
Simple fibroadenomas are not associated with an increased risk of breast cancer.
Therapeutic Targets:
Treatment is usually conservative (observation)
Excision may be performed for large or symptomatic lesions.
Differential Diagnosis
Similar Entities:
Complex fibroadenoma
Phyllodes tumor.
Distinguishing Features:
Complex fibroadenomas have complex features
Phyllodes tumors have a more cellular stroma and a leaf-like architecture.
Diagnostic Challenges:
The main challenge is distinguishing a simple fibroadenoma from a benign phyllodes tumor on a core needle biopsy.
Rare Variants:
Not applicable.
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]