Definition/General
Introduction:
Phyllodes tumor with apocrine carcinoma is an extremely rare malignant phyllodes tumor where the stromal component contains apocrine carcinoma characterized by large eosinophilic cells with abundant granular cytoplasm and apical snouts.
Origin:
Develops from intralobular breast stroma with differentiation toward apocrine carcinoma
May arise through specific differentiation pathways leading to apocrine-type secretory features.
Classification:
WHO Classification categorizes this as malignant phyllodes tumor with heterologous elements
Apocrine carcinoma component shows characteristic large cells with abundant eosinophilic cytoplasm.
Epidemiology:
Exceptionally rare with fewer than 10 cases reported worldwide
Peak age 50-70 years
Female predominance
Prognosis intermediate between ductal and special types.
Clinical Features
Presentation:
Large, slowly to moderately growing breast mass
Usually presents as well-circumscribed to irregular mass
May show gradual enlargement over months
Often clinically indeterminate.
Symptoms:
Progressive breast enlargement
Usually painless
May have nipple discharge if connected to ductal system
Breast asymmetry
Constitutional symptoms rare.
Risk Factors:
Previous phyllodes tumor history
Older age
Family history of breast cancer
Previous breast disease
Hormonal factors possible.
Screening:
Often detected on mammographic screening
Clinical examination may not detect specific features
Mammography shows mass lesion
Core needle biopsy essential for diagnosis.
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Gross Description
Appearance:
Large, well-circumscribed to irregular mass with firm consistency
Cut surface shows gray-white to tan areas
May have cystic changes
Solid predominant pattern.
Characteristics:
Size typically >3 cm (range 2-10 cm)
Firm consistency
Variable circumscription
Gray-white to brown coloration
Possible cystic areas.
Size Location:
Can occur in any breast region
Usually involves moderate breast tissue
Unilateral presentation
May have irregular borders.
Multifocality:
Typically unifocal mass
Apocrine areas may be multifocal within tumor
Growth pattern variable
Local extension possible.
Microscopic Description
Histological Features:
Biphasic tumor with epithelial and mesenchymal components
Apocrine carcinoma areas show large cells with abundant eosinophilic, granular cytoplasm and characteristic apical snouts.
Cellular Characteristics:
Large polygonal cells with abundant eosinophilic cytoplasm
Vesicular nuclei with prominent nucleoli
Apical snouts (decapitation secretion)
Moderate to high nuclear grade.
Architectural Patterns:
Solid nests and sheets
Glandular pattern with apocrine features
Papillary architecture possible
Stromal invasion with desmoplastic response.
Grading Criteria:
Grade 2-3 typically
Moderate to high nuclear grade
Moderate mitotic activity
Apocrine cytomorphology
Architectural complexity variable.
Immunohistochemistry
Positive Markers:
Gross cystic disease fluid protein-15 (GCDFP-15) positive
Androgen receptor strongly positive
Cytokeratins positive
EMA positive
Epithelial component: CK7+.
Negative Markers:
Estrogen receptor usually negative
Progesterone receptor usually negative
HER2 variable (may be positive)
TTF-1 negative.
Diagnostic Utility:
GCDFP-15 confirms apocrine differentiation
Androgen receptor strongly positive in apocrine tumors
ER/PR negativity with AR positivity characteristic.
Molecular Subtypes:
Apocrine molecular subtype
Androgen receptor-positive
HER2-enriched or luminal androgen receptor subtype possible.
Molecular/Genetic
Genetic Mutations:
PIK3CA mutations common in apocrine tumors
TP53 mutations variable
PTEN alterations
Androgen receptor pathway activation.
Molecular Markers:
Apocrine gene expression signature
High androgen receptor expression
Variable HER2 amplification
Luminal androgen receptor profile.
Prognostic Significance:
Androgen receptor status affects prognosis and treatment options
HER2 status determines targeted therapy eligibility
Generally intermediate prognosis.
Therapeutic Targets:
Androgen receptor antagonists (enzalutamide)
Anti-HER2 therapy if amplified
PI3K/mTOR inhibitors
CDK4/6 inhibitors possible.
Differential Diagnosis
Similar Entities:
Primary apocrine carcinoma of breast
Invasive ductal carcinoma with apocrine features
Apocrine adenosis
Apocrine metaplasia
Metastatic renal cell carcinoma.
Distinguishing Features:
Phyllodes with apocrine: Leaf-like areas, GCDFP-15+
Primary apocrine: No phyllodes component
Renal cell: RCC marker+, different clinical presentation.
Diagnostic Challenges:
Recognition of apocrine features
Distinction from other eosinophilic tumors
Assessment of invasion vs metaplasia
Immunohistochemical interpretation.
Rare Variants:
Apocrine carcinoma with squamous differentiation
Mixed apocrine and ductal carcinoma
Apocrine carcinoma with neuroendocrine features.
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]