Definition/General
Introduction:
Fat necrosis is a benign inflammatory process in the breast that results from injury to the adipose tissue
It can mimic malignancy clinically and mammographically.
Origin:
It is caused by trauma to the breast, including surgery, radiation, or accidental injury
In many cases, the patient does not recall a specific traumatic event.
Classification:
It is a benign, non-proliferative breast lesion.
Epidemiology:
It is a common finding, especially in women with large breasts who are more prone to trauma.
Clinical Features
Presentation:
Can present as a painless, firm, irregular, palpable mass
Skin retraction or dimpling can occur, further mimicking carcinoma.
Symptoms:
A painless breast lump is the most common symptom
It can also be tender.
Risk Factors:
History of breast trauma, surgery, or radiation.
Screening:
Mammography can show a spiculated mass, architectural distortion, or calcifications (classically coarse or eggshell-like), which can be suspicious for malignancy.
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Gross Description
Appearance:
An ill-defined, firm, nodular lesion
The cut surface can be yellow-gray and may contain chalky white deposits (saponification) or cystic spaces filled with oily fluid (oil cysts).
Characteristics:
The lesion can be hemorrhagic in the early stages.
Size Location:
Size is variable.
Multifocality:
Can be multifocal if the trauma was extensive.
Microscopic Description
Histological Features:
The microscopic features vary with the age of the lesion
Early lesions show hemorrhage and an inflammatory infiltrate of neutrophils and macrophages
Later lesions are characterized by anucleated adipocytes, foamy macrophages (lipophages), multinucleated giant cells, and lymphocytes
Fibrosis and calcification are seen in late stages.
Cellular Characteristics:
The key cells are the foamy macrophages (lipophages) that have phagocytosed lipid.
Architectural Patterns:
The process is centered on necrotic fat lobules.
Grading Criteria:
This is a benign lesion.
Immunohistochemistry
Positive Markers:
Not typically required for diagnosis.
Negative Markers:
Not typically required for diagnosis.
Diagnostic Utility:
IHC is not used for diagnosis.
Molecular Subtypes:
Molecular subtyping is not relevant for this benign condition.
Molecular/Genetic
Genetic Mutations:
This is a benign condition and is not associated with specific genetic mutations.
Molecular Markers:
No specific molecular markers are routinely used for diagnosis.
Prognostic Significance:
Fat necrosis is a benign condition and is not associated with an increased risk of breast cancer.
Therapeutic Targets:
No treatment is required
Biopsy is often performed to exclude malignancy.
Differential Diagnosis
Similar Entities:
Invasive carcinoma
Granulomatous mastitis.
Distinguishing Features:
Invasive carcinoma is composed of malignant epithelial cells
Granulomatous mastitis is centered on lobules and has well-formed granulomas.
Diagnostic Challenges:
The main challenge is the clinical and mammographic mimicry of carcinoma
The presence of foamy macrophages and anucleated adipocytes on biopsy is diagnostic.
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]