Definition/General

Introduction:
-Lobular carcinoma in situ (LCIS) arising within a fibroadenoma is the most common type of carcinoma to be found in a fibroadenoma
-The LCIS is confined to the epithelial component of the fibroadenoma.
Origin: The LCIS arises from the epithelial component of the fibroadenoma.
Classification: The LCIS is classified according to the standard criteria.
Epidemiology: It is most common in perimenopausal and postmenopausal women.

Clinical Features

Presentation: Presents as a palpable breast mass, often with a recent history of growth.
Symptoms: A breast lump is the most common symptom.
Risk Factors: The risk factors are those for breast cancer in general.
Screening: Mammography may show a well-circumscribed mass with suspicious features, such as indistinct margins or calcifications.

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Gross Description

Appearance: The gross appearance is usually that of a fibroadenoma.
Characteristics: Gross findings are not specific for this microscopic diagnosis.
Size Location: Gross findings are not specific for this microscopic diagnosis.
Multifocality: Gross findings are not specific for this microscopic diagnosis.

Microscopic Description

Histological Features:
-The lesion is a fibroadenoma with a focus of LCIS
-The LCIS is characterized by a proliferation of small, discohesive cells that fill and expand the ductules within the fibroadenoma.
Cellular Characteristics: The cytological features are those of LCIS.
Architectural Patterns: The background is that of a fibroadenoma.
Grading Criteria: LCIS is a low-grade lesion.

Immunohistochemistry

Positive Markers: The LCIS cells are ER and PR positive.
Negative Markers: The key finding is the loss of E-cadherin expression in the LCIS cells.
Diagnostic Utility: IHC for E-cadherin is essential to confirm the lobular nature of the in situ carcinoma.
Molecular Subtypes: Molecular subtyping is not relevant for this pre-invasive lesion.

Molecular/Genetic

Genetic Mutations: Loss of the CDH1 gene is the key genetic event.
Molecular Markers: No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
-LCIS arising in a fibroadenoma is a risk factor for subsequent invasive carcinoma in both breasts
-The management is similar to that of LCIS found in the native breast.
Therapeutic Targets:
-Treatment is usually conservative, with follow-up
-Risk-reducing medication may be considered.

Differential Diagnosis

Similar Entities:
-Fibroadenoma with ALH
-Fibroadenoma with DCIS.
Distinguishing Features:
-The distinction between ALH and LCIS is quantitative
-DCIS is E-cadherin positive.
Diagnostic Challenges: The main challenge is to identify the LCIS within the fibroadenoma.
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]