BREAST CYTOPATHOLOGY

54 2. Non-neoplastic and Proliferative Lesions
or, more commonly, coexist with other breast lesions
(gynecomastia, hamartoma, etc.).
• Some cases are proven to be hormonally related.
• This hyperplasia is more common in premenopausal women
and postmenopausal women receiving hormone replacement
therapy. Some cases show size fluctuations during
menses.
• Myofibroblasts in pseudoangiomatous stromal hyperplasia
immunoexpress hormone receptors (particularly
progesterone).
• This hyperplasia grows slowly. Rarely has rapid growth
been reported in immunocompromised patients.
• Local excision is curative in most cases.
• Its exact nature is unclear; it could be related to an underlying
neoplastic process, as some cases recur locally after
excision.
Cytomorphologic Characteristics
• Aspirates are often extremely scant and mostly nondiagnostic
(because of stromal hyalinization).
• When diagnostic, the smears are scantly cellular and
display cohesive benign-appearing ductal fragments,
often in flat sheets, less often as branching structures,
“fibroadenomalike”
• Rare, bland-appearing spindled cells
• Numerous single bipolar naked nuclei
• Bipolar uniform spindled cells
• Hypocellular loose stromal tissue fragments or fibrillary
matrix
• No cellular pleomorphism, no mitoses
Pitfalls and Differential Diagnosis
• Fibroadenoma
• Phyllodes tumor
• Myofibroblastoma
• Metaplastic carcinoma