Definition/General

Introduction:
-Phyllodes tumor with synovial sarcoma represents an extremely rare malignant phyllodes tumor where the stromal component shows synovial sarcoma differentiation
-This is a high-grade malignant variant with aggressive behavior and poor prognosis.
Origin:
-Arises from intralobular stroma of the breast with secondary development of synovial sarcoma within the stromal component
-May arise de novo or from malignant transformation of benign/borderline phyllodes tumor.
Classification:
-WHO Classification categorizes this as malignant phyllodes tumor with heterologous sarcomatous elements
-Represents one of the rarest forms of malignant phyllodes tumor with synovial sarcoma as stromal component.
Epidemiology:
-Extremely rare with fewer than 50 cases reported in literature
-Peak age 40-60 years
-More aggressive than conventional malignant phyllodes tumor
-High propensity for local recurrence and distant metastasis.

Clinical Features

Presentation:
-Rapidly growing breast mass
-Large size at presentation (often >10 cm)
-May show surface ulceration
-Skin involvement possible in advanced cases.
Symptoms:
-Painful, rapidly enlarging breast mass
-Breast asymmetry
-Skin changes over the tumor
-Nipple discharge rare
-Weight loss in advanced cases.
Risk Factors:
-Previous history of phyllodes tumor
-Genetic predisposition to sarcomas
-Radiation exposure
-Li-Fraumeni syndrome
-Previous breast trauma.
Screening:
-No specific screening guidelines
-Clinical breast examination
-Mammography and ultrasound
-MRI for extent evaluation
-CT chest for metastasis evaluation.

Master Phyllodes Tumor with Synovial Sarcoma Pathology with RxDx

Access 100+ pathology videos and expert guidance with the RxDx app

Gross Description

Appearance:
-Large, bulky mass with bosselated surface
-Cut surface shows heterogeneous appearance with solid and cystic areas
-Areas of necrosis and hemorrhage common.
Characteristics:
-Size typically >5 cm (range 3-25 cm)
-Firm to hard consistency
-Irregular borders
-Leaf-like clefts may be present
-Geographic necrosis.
Size Location:
-Can involve entire breast
-Central or upper quadrant location common
-Unilateral involvement
-May extend to chest wall.
Multifocality:
-Usually unifocal massive lesion
-Satellite nodules possible
-Skin involvement in large tumors
-Chest wall invasion in advanced cases.

Microscopic Description

Histological Features:
-Biphasic tumor with epithelial and mesenchymal components
-Stromal hypercellularity with fascicular pattern
-Spindle cells with high mitotic activity
-Leaf-like architecture focally preserved.
Cellular Characteristics:
-Synovial sarcoma areas show monomorphic spindle cells
-High nuclear grade
-Brisk mitotic activity (>10 per 10 HPF)
-Focal epithelioid areas possible.
Architectural Patterns:
-Monophasic synovial sarcoma pattern most common
-Fascicular arrangement of spindle cells
-Herringbone pattern
-Hemangiopericytoma-like vasculature.
Grading Criteria:
-High-grade malignant phyllodes tumor criteria
-Stromal overgrowth present
-High mitotic rate
-Marked nuclear atypia
-Geographic necrosis.

Immunohistochemistry

Positive Markers:
-Synovial sarcoma areas: TLE1+, SS18+, EMA focal+, CD99+, BCL2+
-Epithelial component: CK7+, CK19+, EMA+.
Negative Markers:
-Synovial sarcoma areas: Desmin-, S-100-, CD34-, SMA-
-ER/PR negative
-HER2 negative.
Diagnostic Utility:
-TLE1 positive in >90% of synovial sarcomas
-SS18 break-apart FISH confirms diagnosis
-Helps distinguish from other sarcomas.
Molecular Subtypes:
-SS18-SSX fusion variants
-Type 1 (SS18-SSX1) more common in monophasic
-Type 2 (SS18-SSX2) in biphasic
-Prognostic implications.

Molecular/Genetic

Genetic Mutations:
-SS18-SSX1 fusion (60-70%)
-SS18-SSX2 fusion (30-40%)
-Rare SS18-SSX4 fusion
-p53 mutations possible.
Molecular Markers:
-SS18 gene rearrangement (pathognomonic)
-TLE1 overexpression
-High Ki-67 index (>30%)
-FISH confirmation essential.
Prognostic Significance:
-SS18-SSX fusion type may affect prognosis
-High mitotic rate predicts poor outcome
-Tumor size >10 cm adverse factor.
Therapeutic Targets:
-Limited targeted options
-mTOR pathway inhibitors under study
-Immune checkpoint inhibitors in trials
-Pazopanib shows activity.

Differential Diagnosis

Similar Entities:
-Malignant phyllodes tumor with fibrosarcoma
-Primary breast synovial sarcoma
-Metaplastic carcinoma with sarcomatoid features
-Stromal sarcoma.
Distinguishing Features:
-Phyllodes with synovial sarcoma: Leaf-like areas, SS18-SSX fusion
-Primary synovial sarcoma: No epithelial component
-Metaplastic carcinoma: Cytokeratin positive.
Diagnostic Challenges:
-Recognition of synovial sarcoma features
-Distinction from other sarcomas
-FISH confirmation required
-Assessment of margins difficult.
Rare Variants:
-Biphasic synovial sarcoma variant
-Calcifying variant
-Poorly differentiated areas
-Combined with other sarcomas.

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]

Prognostic Factors

Prognostic factors: [list factors]

Final Diagnosis

Final diagnosis: [complete diagnosis]