Phyllodes tumor is a rare fibroepithelial neoplasm arising from breast stroma, accounting for 0.3-1% of all breast tumors. Named from the Greek 'phyllon' (leaf) — leaf-like projections are characteristic on histopathology. Phyllodes tumors are classified into three groups: benign (60-75%), borderline (15-20%), and malignant (10-25%). Clinically presents as a rapidly growing, large (usually >3-4 cm), well-circumscribed breast mass. Differentiation from fibroadenoma may be difficult by clinical and imaging features — may be misdiagnosed as 'giant fibroadenoma.' On ultrasound, well-circumscribed, oval/lobulated, heterogeneously hypoechoic mass with cystic clefts (cleft-like spaces) is the most characteristic finding of phyllodes tumor. On MRI, prominent enhancement and high signal cystic components on T2 support the diagnosis. Treatment is wide local excision (>1 cm clear margins) with recurrence risk — malignant phyllodes tumors can metastasize hematogenously to the lungs.
Age Range
35-55
Peak Age
45
Gender
Female predominant
Prevalence
Uncommon
Phyllodes tumor is a neoplastic proliferation of fibroblast/myofibroblast cells of breast stroma (periductal stroma). Unlike fibroadenoma, the stromal component is markedly dominant and shows increased cellularity. The characteristic 'leaf-like' (phylloid) architecture results from stromal component forming leaf-shaped projections surrounding epithelial ducts — these projections are reflected in imaging as cystic clefts (cleft-like spaces). Cystic cleft formation results from stromal proliferation compressing ducts and lobules creating slit-like spaces — these spaces may be filled with serous fluid or hemorrhagic material. Rapid growth stems from high mitotic activity of stromal cells — proliferation rate is significantly higher than fibroadenoma even in benign phyllodes tumors. In malignant variants, increased stromal atypia, necrosis, increased mitoses (>10/10 HPF), and infiltrative margins develop. Hematogenous metastasis (axillary lymph node involvement is rare — lymphatic spread is not expected) occurs particularly to lungs and results from sarcoma-like behavior of the stromal component.
Anechoic/hypoechoic cystic clefts within a well-circumscribed heterogeneous solid mass — corresponding to leaf-like stromal projections of the tumor. Most important imaging finding for differentiation from fibroadenoma. Also seen as T2-hyperintense clefts on MRI.
Anechoic or hypoechoic cystic clefts (cleft-like spaces) within a well-circumscribed, heterogeneously hypoechoic solid mass. These clefts correspond to the leaf-like projections of the tumor. Clefts are thin, elongated, and irregularly shaped, sometimes resembling septations.
Report Sentence
Multiple cystic clefts (cleft-like spaces) are observed within a well-circumscribed, lobulated, heterogeneously hypoechoic solid mass, suggesting phyllodes tumor; core biopsy is recommended.
Increased vascularity within and around the tumor on color Doppler. Vascular structures may show irregular distribution. In large tumors, feeding vessels may be detected. Vascularity is more prominent in malignant variants than benign variants.
Report Sentence
Increased vascularity with peripheral feeding vessels is observed within the mass on color Doppler, consistent with phyllodes tumor.
Large, well-circumscribed mass with lobulated contours and high density. Calcification typically absent or minimal. Halo (lucent rim) may be seen. Peripheral vascular structures may be prominent. Size usually >3 cm. May be difficult to differentiate from fibroadenoma mammographically.
Report Sentence
A large, well-circumscribed mass with lobulated contours and high density is observed on mammography; phyllodes tumor or giant fibroadenoma should be considered in the differential diagnosis.
High signal cystic components and leaf-like projections within the mass on T2-weighted series. Solid component shows intermediate signal. Cystic areas may be cleft-shaped or lobulated. Marked heterogeneity on T2 is the most distinguishing MRI feature of phyllodes tumor.
Report Sentence
Multiple T2-hyperintense cystic components and leaf-like projections within a heterogeneous solid mass are observed on T2-weighted MRI, consistent with phyllodes tumor.
Rapid and prominent enhancement of solid components on contrast-enhanced MRI. Kinetic curve may show Type II (plateau) or Type III (washout) — washout kinetics is more common especially in malignant variants. Enhancement is heterogeneous with cystic clefts showing no enhancement.
Report Sentence
Prominent heterogeneous enhancement of solid components is observed on contrast-enhanced MRI with Type II (plateau) kinetic curve; cystic clefts show no enhancement.
Large solid mass with well-circumscribed, oval or lobulated contours, showing hypoechoic or heterogeneous echotexture. May show posterior acoustic enhancement (due to cystic components) or variable posterior acoustic features. Size usually >3 cm, average 5-7 cm.
Report Sentence
A well-circumscribed, lobulated, heterogeneous solid mass measuring approximately 6 cm with posterior acoustic enhancement is observed on ultrasound.
Criteria
Low stromal cellularity, <5 mitoses/10 HPF, pushing margins, minimal stromal atypia. Comprises 60-75% of all phyllodes tumors. Local recurrence risk 10-17%.
Distinct Features
Subtype most difficult to differentiate from fibroadenoma on imaging. More homogeneous US appearance. Less heterogeneity on MRI and may show Type I kinetics. Treatment: wide local excision (>1 cm margin).
Criteria
Moderate stromal cellularity, 5-9 mitoses/10 HPF, pushing or focally infiltrative margins, moderate stromal atypia. Comprises 15-20% of all phyllodes tumors. Local recurrence risk 15-25%.
Distinct Features
Features between benign and malignant. Difficult to differentiate from benign variant on imaging. Treatment: wide local excision or mastectomy (depending on size and location).
Criteria
High stromal cellularity, ≥10 mitoses/10 HPF, infiltrative margins, marked stromal atypia, stromal overgrowth (pure stromal areas without epithelial component). Comprises 10-25% of all phyllodes tumors. Local recurrence 20-40%, distant metastasis 15-25% (lung).
Distinct Features
More heterogeneous on imaging, larger size, more prominent cystic clefts and necrosis areas. Type III kinetics (washout). Irregular margins may be seen. Chest CT required for lung metastasis screening. Treatment: wide local excision or mastectomy + adjuvant radiotherapy.
Distinguishing Feature
Fibroadenoma is generally smaller (<3 cm), homogeneously hypoechoic, and does not contain cystic clefts. Fibroadenoma occurs at younger age (15-35). Rapid growth is not expected in fibroadenoma. Fibroadenoma may show coarse calcification on mammography, phyllodes generally does not.
Distinguishing Feature
IDC forms spiculated or irregularly marginated mass — phyllodes tumor is well-circumscribed and lobulated. IDC may show calcification and architectural distortion. IDC is epithelial, phyllodes is stromal in origin. IDC causes axillary LAP, phyllodes rarely.
Distinguishing Feature
Primary breast sarcoma is rare and is generally a pure stromal tumor — no epithelial component. Stromal overgrowth in malignant phyllodes tumor may mimic sarcoma. Histopathologically, presence of residual epithelial component in phyllodes is differentiating.
Distinguishing Feature
Hamartoma appears as 'breast within a breast' with well-circumscribed mass containing fat and glandular tissue — phyllodes tumor is homogeneous solid or mixed solid-cystic and does not contain fat. Growth in hamartoma is slow.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
6-monthPhyllodes tumor requires surgical excision in all subtypes — preoperative diagnosis should be made with core biopsy. Gold standard treatment is wide local excision with clear margins (≥1 cm) — risk of local recurrence is high with inadequate margins (20-40%). Mastectomy may be needed in malignant phyllodes tumors. Axillary lymph node dissection is not required — hematogenous spread is dominant. In malignant phyllodes, lung metastasis should be screened with chest CT. Adjuvant radiotherapy may reduce recurrence in malignant and borderline tumors. Chemotherapy efficacy is limited. Postoperative follow-up: breast US/mammography at 6-month intervals (minimum 5 years). 5-year survival in malignant phyllodes is 60-80%.
Treatment for phyllodes tumor is wide excision (at least 1 cm surgical margin). Enucleation is inadequate with high local recurrence rate. Malignant phyllodes can metastasize hematogenously (lung most common). Differentiation from fibroadenoma may be difficult on core biopsy, excisional biopsy may be required.