Definition/General
Introduction:
Inflammatory breast carcinoma (IBC) is a rare and very aggressive form of breast cancer that accounts for 1-5% of all breast cancers
It is defined by clinical signs of inflammation in the breast, such as redness, swelling, and warmth, with or without an underlying palpable mass.
Origin:
IBC is a clinical diagnosis, not a specific histological subtype
The underlying histology is most often a high-grade invasive ductal carcinoma
The inflammatory signs are caused by tumor emboli obstructing dermal lymphatic vessels.
Classification:
It is classified as a clinical entity (T4d in the TNM staging system)
The diagnosis requires the characteristic clinical presentation and pathological confirmation of dermal lymphatic invasion by tumor cells.
Epidemiology:
It tends to affect younger women compared to other breast cancers
It is more common in African American women
It has a rapid onset and progression.
Clinical Features
Presentation:
Rapid onset of breast erythema, edema, and warmth
The breast is often tender and enlarged
A distinct lump may or may not be present
The skin may have a peau d'orange (orange peel) appearance.
Symptoms:
Breast swelling, pain, tenderness, and itching
The symptoms can be mistaken for mastitis, but they do not respond to antibiotics.
Risk Factors:
Younger age and African American race are known risk factors
Other general breast cancer risk factors may also apply.
Screening:
IBC is typically not detected by screening mammography as it often does not form a distinct mass
The diagnosis is usually made based on the acute clinical presentation.
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Gross Description
Appearance:
There may not be a discrete tumor mass
The breast tissue is often diffusely indurated and edematous
The skin is thickened and erythematous.
Characteristics:
If a mass is present, it is usually ill-defined
The overall breast is enlarged and heavy.
Size Location:
The process typically involves the entire breast.
Multifocality:
IBC is considered a diffuse disease process.
Microscopic Description
Histological Features:
The key pathological finding is the presence of tumor emboli within dermal lymphatic vessels
The underlying invasive carcinoma is usually a high-grade ductal carcinoma, no special type
The tumor cells are pleomorphic with high mitotic activity.
Cellular Characteristics:
The tumor cells are large, with high-grade nuclear features, including irregular nuclear contours, coarse chromatin, and prominent nucleoli.
Architectural Patterns:
The underlying carcinoma can have various patterns, but it is most commonly a poorly differentiated ductal carcinoma.
Grading Criteria:
The underlying carcinoma is almost always high-grade (Grade 3).
Immunohistochemistry
Positive Markers:
The IHC profile depends on the underlying carcinoma
Many cases are ER-positive or HER2-positive
A significant proportion are triple-negative.
Negative Markers:
The IHC profile is variable.
Diagnostic Utility:
IHC is used to characterize the underlying carcinoma (ER, PR, HER2 status) to guide therapy
D2-40 can be used to highlight the lymphatic vessels containing tumor emboli.
Molecular Subtypes:
IBC can be of any molecular subtype, but it is more frequently HER2-positive or triple-negative compared to non-inflammatory breast cancers.
Molecular/Genetic
Genetic Mutations:
TP53 mutations are common
The genomic profile is complex and heterogeneous
Overexpression of genes involved in angiogenesis and inflammation is a feature.
Molecular Markers:
E-cadherin is often overexpressed, which may contribute to the formation of tumor emboli
RhoC GTPase overexpression is also implicated in the aggressive phenotype.
Prognostic Significance:
IBC has a very poor prognosis with a high risk of early recurrence and distant metastasis
The 5-year survival rate is significantly lower than for other types of breast cancer.
Therapeutic Targets:
Treatment is multimodal, including neoadjuvant chemotherapy, surgery, and radiation
HER2-targeted therapy is used for HER2-positive cases
Hormonal therapy is used for ER-positive cases.
Differential Diagnosis
Similar Entities:
Mastitis (infectious)
Radiation dermatitis
Other causes of skin inflammation
Lymphoma or leukemia cutis.
Distinguishing Features:
Mastitis typically responds to antibiotics and may be associated with lactation
Radiation dermatitis has a clear history of radiation exposure
A skin biopsy showing dermal lymphatic invasion by carcinoma is diagnostic of IBC.
Diagnostic Challenges:
The clinical presentation can mimic infection, leading to a delay in diagnosis
A high index of suspicion is required
A skin punch biopsy is necessary to confirm the diagnosis.
Rare Variants:
The underlying histology can be lobular carcinoma or other rare subtypes, but ductal is the most common.
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]