Definition/General
Introduction:
Apocrine atypia is a term used for a spectrum of lesions characterized by a proliferation of apocrine cells with cytological atypia
It is a challenging and controversial area of breast pathology
It is considered a risk factor for breast cancer.
Origin:
It arises from the terminal duct-lobular unit (TDLU).
Classification:
There is no universally accepted classification
It is generally considered a lesion with atypia that falls short of apocrine DCIS
It can be part of a flat or papillary proliferation.
Epidemiology:
It is an uncommon finding in breast biopsies.
Clinical Features
Presentation:
Apocrine atypia is an incidental microscopic finding.
Symptoms:
Asymptomatic.
Risk Factors:
There are no well-established risk factors.
Screening:
It can be associated with microcalcifications on mammography.
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Gross Description
Appearance:
There are no specific gross findings.
Characteristics:
Gross findings are not specific for this microscopic diagnosis.
Size Location:
Gross findings are not specific for this microscopic diagnosis.
Multifocality:
Can be multifocal.
Microscopic Description
Histological Features:
The lesion is characterized by a proliferation of apocrine cells with nuclear atypia
The atypia is defined by nuclear enlargement (2-3 times the size of a red blood cell), hyperchromasia, and prominent nucleoli
The architectural pattern can be flat, papillary, or cribriform.
Cellular Characteristics:
The cells have abundant, granular, eosinophilic cytoplasm
The key feature is the cytological atypia, which is more pronounced than in apocrine hyperplasia but less than in apocrine DCIS.
Architectural Patterns:
The proliferation can be single-layered (flat) or multilayered (hyperplastic).
Grading Criteria:
This is a lesion with atypia, considered a step below DCIS.
Immunohistochemistry
Positive Markers:
The cells are positive for GCDFP-15 and AR
They are typically negative for ER and PR.
Negative Markers:
Usually negative for ER and PR.
Diagnostic Utility:
IHC can confirm apocrine differentiation.
Molecular Subtypes:
Molecular subtyping is not relevant for this pre-invasive lesion.
Molecular/Genetic
Genetic Mutations:
Apocrine atypical lesions show a high frequency of chromosomal alterations, similar to those seen in apocrine DCIS and invasive apocrine carcinoma.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
Apocrine atypia is considered a risk factor for developing invasive breast cancer
The magnitude of the risk is not well-defined but is thought to be similar to that of ADH.
Therapeutic Targets:
Management is controversial
Excision is often recommended to exclude a more significant lesion.
Differential Diagnosis
Similar Entities:
Apocrine hyperplasia
Apocrine DCIS.
Distinguishing Features:
Apocrine hyperplasia lacks significant cytological atypia
Apocrine DCIS shows a greater degree of cytological atypia and/or architectural complexity (e.g., extensive cribriform pattern, comedonecrosis).
Diagnostic Challenges:
The distinction between apocrine atypia and apocrine DCIS is subjective and can be difficult
There is significant interobserver variability.
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]