Definition/General
Introduction:
Cysts are fluid-filled sacs within the breast
They are a common component of fibrocystic changes and are one of the most common causes of a breast lump
They can be simple or complex.
Origin:
Cysts arise from the terminal duct-lobular unit (TDLU) due to the obstruction and dilation of the acini.
Classification:
Cysts are classified as simple, complicated, or complex based on their ultrasound features
Pathologically, they are a form of non-proliferative benign breast disease.
Epidemiology:
They are extremely common, especially in women aged 35 to 50
They are rare after menopause unless a woman is on hormone replacement therapy.
Clinical Features
Presentation:
Presents as a smooth, mobile, often tender, palpable mass
The size and tenderness can fluctuate with the menstrual cycle.
Symptoms:
A palpable lump is the most common symptom
Breast pain or tenderness is also common.
Risk Factors:
Hormonal fluctuations of the menstrual cycle are the main risk factor.
Screening:
Ultrasound is the best imaging modality to characterize a cyst, showing a well-defined, anechoic lesion with posterior acoustic enhancement.
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Gross Description
Appearance:
A well-circumscribed, thin-walled sac filled with clear, serous, or turbid fluid
The cysts can have a blue-dome appearance when unopened.
Characteristics:
The size can range from microscopic (microcysts) to several centimeters (macrocysts).
Size Location:
Can occur anywhere in the breast.
Multifocality:
Often multiple and bilateral.
Microscopic Description
Histological Features:
The cyst is lined by a layer of cuboidal to flattened epithelial cells
A myoepithelial layer is present
The lining often shows apocrine metaplasia.
Cellular Characteristics:
The epithelial cells are bland, without atypia.
Architectural Patterns:
A simple cystic structure is the key feature.
Grading Criteria:
This is a benign lesion.
Immunohistochemistry
Positive Markers:
Not typically required for diagnosis.
Negative Markers:
Not typically required for diagnosis.
Diagnostic Utility:
IHC is not used for the diagnosis of simple cysts.
Molecular Subtypes:
Molecular subtyping is not relevant for this benign condition.
Molecular/Genetic
Genetic Mutations:
This is a benign condition and is not associated with specific genetic mutations.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
Simple cysts are not associated with an increased risk of breast cancer.
Therapeutic Targets:
Asymptomatic simple cysts do not require treatment
Large or painful cysts can be aspirated for symptomatic relief.
Differential Diagnosis
Similar Entities:
Cystic papilloma
Cystic papillary carcinoma
Galactocele.
Distinguishing Features:
Papillary lesions will have an intracystic mass
A galactocele is a milk-filled cyst that occurs during lactation.
Diagnostic Challenges:
The main challenge is to evaluate the lining of the cyst for any proliferative or atypical changes.
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]