Definition/General
Introduction:
An intraductal papilloma is a benign papillary tumor that arises from the epithelium of the breast ducts
They can be solitary or multiple.
Origin:
They arise from the ductal epithelium.
Classification:
They are classified as benign proliferative breast lesions
They can be central (solitary, in large ducts) or peripheral (multiple, in TDLUs).
Epidemiology:
Solitary papillomas are most common in perimenopausal women
Multiple papillomas tend to occur in younger women.
Clinical Features
Presentation:
Solitary central papillomas typically present with serous or bloody nipple discharge
Peripheral papillomas are usually asymptomatic and are often an incidental finding.
Symptoms:
Nipple discharge is the classic symptom of a central papilloma
A palpable subareolar mass may be present.
Risk Factors:
There are no well-established risk factors.
Screening:
Ductography can be used to visualize the filling defect in the duct
On ultrasound, they appear as an intraductal mass.
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Gross Description
Appearance:
A friable, polypoid mass within a dilated duct
The size is usually small, less than 1 cm.
Characteristics:
The papilloma is attached to the duct wall by a stalk.
Size Location:
Central papillomas are located in the large subareolar ducts
Peripheral papillomas are in the TDLUs.
Multifocality:
Peripheral papillomas are often multiple (papillomatosis).
Microscopic Description
Histological Features:
The papilloma is composed of fibrovascular cores lined by a double layer of epithelial and myoepithelial cells
The architecture is complex and branching.
Cellular Characteristics:
The epithelial and myoepithelial cells are bland, with no atypia
Apocrine metaplasia is common.
Architectural Patterns:
A branching papillary architecture is the key feature.
Grading Criteria:
This is a benign lesion
When atypia is present, it is called an atypical papilloma.
Immunohistochemistry
Positive Markers:
The myoepithelial cell layer is highlighted by myoepithelial markers such as p63 and calponin.
Negative Markers:
Not typically required for diagnosis.
Diagnostic Utility:
IHC for myoepithelial markers is crucial to differentiate a benign papilloma from papillary DCIS or invasive papillary carcinoma, which lack a myoepithelial layer in the papillae or invasive component, respectively.
Molecular Subtypes:
Molecular subtyping is not relevant for this benign condition.
Molecular/Genetic
Genetic Mutations:
Papillomas can have mutations in genes like PIK3CA and AKT1.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
Solitary papillomas are associated with a small increased risk (about 2 fold) of breast cancer
Multiple papillomas are associated with a higher risk.
Therapeutic Targets:
Surgical excision is the standard treatment to confirm the diagnosis and exclude atypia or carcinoma.
Differential Diagnosis
Similar Entities:
Papillary DCIS
Encapsulated papillary carcinoma
Solid papillary carcinoma
Invasive papillary carcinoma.
Distinguishing Features:
Malignant papillary lesions are distinguished by the absence of a myoepithelial layer within the papillae (in papillary DCIS) or at the periphery of the lesion (in encapsulated and solid papillary carcinoma), and by the presence of invasion (in invasive papillary carcinoma).
Diagnostic Challenges:
The main challenge is distinguishing a benign papilloma from a papillary carcinoma on a core needle biopsy, as the myoepithelial layer can be attenuated and difficult to assess
Excision is often necessary.
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]