Definition/General
Introduction:
Intraductal papillary carcinoma is a term that has been used for several types of papillary lesions, but it most accurately refers to papillary ductal carcinoma in situ (DCIS)
This is a type of DCIS where the malignant cells grow in a papillary pattern within the ducts.
Origin:
It arises from the ductal epithelium.
Classification:
It is a subtype of DCIS
It is distinguished from a benign papilloma by the absence of a myoepithelial layer in the papillae.
Epidemiology:
It is an uncommon form of DCIS
It typically affects postmenopausal women.
Clinical Features
Presentation:
Can present with nipple discharge or as a palpable mass
It can also be detected as mammographic calcifications.
Symptoms:
Nipple discharge is a common symptom.
Risk Factors:
The risk factors are similar to those for other types of DCIS.
Screening:
Mammography may show a mass or calcifications.
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Gross Description
Appearance:
A soft, friable mass within a dilated duct.
Characteristics:
The size is variable.
Size Location:
Usually located in the central part of the breast.
Multifocality:
Can be multifocal.
Microscopic Description
Histological Features:
The lesion is characterized by papillae with fibrovascular cores that are lined by a monotonous population of atypical epithelial cells
The key feature is the absence of a myoepithelial layer lining the papillae.
Cellular Characteristics:
The cells are typically low to intermediate grade, with mild to moderate nuclear atypia.
Architectural Patterns:
A complex, branching papillary architecture is characteristic.
Grading Criteria:
Graded as low, intermediate, or high grade based on nuclear features, similar to other types of DCIS.
Immunohistochemistry
Positive Markers:
The epithelial cells are positive for cytokeratins and are usually ER-positive.
Negative Markers:
The key finding is the absence of myoepithelial markers (e.g., p63, calponin) in the papillae.
Diagnostic Utility:
IHC for myoepithelial markers is essential to distinguish papillary DCIS from a benign intraductal papilloma.
Molecular Subtypes:
Most are of the luminal subtype.
Molecular/Genetic
Genetic Mutations:
The genetic alterations are similar to those of other low-grade DCIS subtypes.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
The prognosis is excellent, as it is an in situ carcinoma
However, it is a risk factor for subsequent invasive carcinoma.
Therapeutic Targets:
Treatment is similar to other forms of DCIS, involving surgery and possibly radiation and endocrine therapy.
Differential Diagnosis
Similar Entities:
Benign intraductal papilloma
Encapsulated papillary carcinoma
Invasive papillary carcinoma.
Distinguishing Features:
Benign papillomas have a myoepithelial layer in the papillae
Encapsulated papillary carcinoma is a distinct entity that is considered an indolent form of invasive cancer
Invasive papillary carcinoma shows stromal invasion.
Diagnostic Challenges:
The main challenge is the distinction from a benign papilloma, which relies on the demonstration of the absence of a myoepithelial layer.
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]