BREAST CYTOPATHOLOGY

Phyllodes Tumor 63
• Low-grade ductal carcinoma (particularly tubular carcinoma)
• Mucinous carcinoma
Phyllodes Tumor
A phyllodes tumor is a rare fibroepithelial breast tumor often
distinguished from fibroadenoma by the presence of a more
prominent and cellular mesenchymal component. It is a
major differential diagnosis of a breast lesion with a significant
spindle cell or mesenchymal component. Although most
phyllodes tumors are benign, low-grade (borderline) and
malignant subtypes are occasionally encountered. Their preoperative
distinction from fibroadenomas (which is not always
possible) is considered clinically significant, as phyllodes
tumors are resected with a wider negative margin in order to
avoid tumor recurrence.
Clinical Features
• Occurrence is rare, accounting for 0.3%–1% of primary
breast tumors.
• Peak incidence is seen much later in life than fibroadenoma
(45–50 years).
• Most patients present with a unilateral slowly enlarging
breast mass, with an average size of 5 cm.
• Approximately 15%–20% of phyllodes tumors recur after
excision.
Cytomorphologic Characteristics
(Figures 3.9 to 3.13)
• Hypercellular smears, biphasic but more often epithelialpredominant
(in benign tumors), with large stromal fragments
(“phyllodes fragments”), often in an anatomizing/
branching pattern