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.

Master Intraductal Papillary Ca Pathology with RxDx

Access 100+ pathology videos and expert guidance with the RxDx app

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]