Definition/General
Introduction:
Primary breast sarcomas are a heterogeneous group of malignant mesenchymal tumors that arise from the connective tissue of the breast
They are extremely rare, accounting for less than 0.1% of all breast malignancies
They are distinct from phyllodes tumors and angiosarcomas.
Origin:
These tumors arise from the non-epithelial, stromal tissues of the breast, such as fibrous tissue, fat, and blood vessels
Unlike carcinomas, they do not originate from the ducts or lobules.
Classification:
Breast sarcomas are classified based on their line of differentiation, similar to soft tissue sarcomas elsewhere in the body
Common subtypes include fibrosarcoma, liposarcoma, and leiomyosarcoma
Angiosarcoma is a specific type of breast sarcoma but is often considered a separate entity.
Epidemiology:
Breast sarcomas can occur at any age, but they are most common in middle-aged and older women
A history of prior radiation therapy to the chest wall is a known risk factor.
Clinical Features
Presentation:
Typically presents as a large, rapidly growing, palpable breast mass
The mass is usually painless and firm
Skin changes such as ulceration can occur with large tumors.
Symptoms:
A painless, enlarging breast lump is the most common symptom
The rapid growth can cause a sensation of pressure or discomfort.
Risk Factors:
Prior radiation therapy is the most well-established risk factor
Lymphedema (Stewart-Treves syndrome) is a risk factor for lymphangiosarcoma
Genetic syndromes like Li-Fraumeni syndrome can also predispose to sarcomas.
Screening:
They are usually diagnosed after a palpable mass is investigated
On mammography, they appear as large, non-calcified masses with indistinct or circumscribed margins.
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Gross Description
Appearance:
A large, fleshy, gray-white mass
The borders can be well-circumscribed or infiltrative
Areas of necrosis and hemorrhage are common.
Characteristics:
The size is typically large at diagnosis
The consistency is often firm, but can be soft or myxoid depending on the subtype.
Size Location:
Can occur anywhere in the breast
Size is highly variable.
Multifocality:
Multifocality is rare.
Microscopic Description
Histological Features:
The histology is that of a sarcoma, with a monotonous proliferation of spindle or pleomorphic cells
The features depend on the subtype (e.g., herringbone pattern in fibrosarcoma, lipoblasts in liposarcoma)
An epithelial component is absent.
Cellular Characteristics:
The tumor cells are mesenchymal in appearance, ranging from uniform spindle cells to highly pleomorphic cells with bizarre nuclei
Mitotic activity is often high.
Architectural Patterns:
The growth pattern is typically diffuse and infiltrative
The tumor cells are arranged in fascicles or sheets.
Grading Criteria:
Grading is based on the French Federation of Cancer Centers Sarcoma Group (FNCLCC) system, which assesses tumor differentiation, mitotic count, and necrosis.
Immunohistochemistry
Positive Markers:
The IHC profile depends on the line of differentiation
For example, desmin and smooth muscle actin in leiomyosarcoma, S100 in liposarcoma
Vimentin is generally positive.
Negative Markers:
Crucially, breast sarcomas are negative for cytokeratins, which rules out metaplastic carcinoma
They are also negative for hormone receptors (ER, PR) and HER2.
Diagnostic Utility:
IHC is essential for diagnosis and subtyping
The main role is to differentiate sarcoma from sarcomatoid (metaplastic) carcinoma.
Molecular Subtypes:
Not applicable in the same way as for breast carcinomas.
Molecular/Genetic
Genetic Mutations:
The genetic alterations are specific to the sarcoma subtype and are similar to those of soft tissue sarcomas elsewhere (e.g., MDM2 amplification in well-differentiated liposarcoma).
Molecular Markers:
Specific translocations can be seen in certain subtypes (e.g., synovial sarcoma).
Prognostic Significance:
The prognosis is generally poor and depends on tumor size, grade, and margin status
Hematogenous metastasis (especially to the lungs) is more common than lymphatic spread
Axillary lymph node metastasis is rare.
Therapeutic Targets:
Treatment is primarily wide surgical excision
The role of adjuvant chemotherapy and radiation is determined by the tumor grade and size, similar to soft tissue sarcomas.
Differential Diagnosis
Similar Entities:
Metaplastic carcinoma
Malignant phyllodes tumor
Cellular fibroadenoma.
Distinguishing Features:
Metaplastic carcinoma has a malignant epithelial component that is positive for cytokeratins
Malignant phyllodes tumor is a biphasic tumor with a benign epithelial component
Cellular fibroadenoma is benign and lacks the atypia and high mitotic rate of sarcoma.
Diagnostic Challenges:
The main challenge is distinguishing breast sarcoma from metaplastic carcinoma, which has significant therapeutic implications
A wide IHC panel is often necessary.
Rare Variants:
Many different subtypes of sarcoma can occur in the breast, all of which are rare.
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]