Pseudoangiomatous Stromal Hyperplasia of the Breast: Multimodality Review With Pathologic Correlation.

Pseudoangiomatous stromal hyperplasia (PASH) is a rare benign breast condition. PASH is thought to be hormonally responsive, and it is usually identified in premenopausal and perimenopausal women. PASH may also be seen in postmenopausal woman on hormone replacement therapy (HRT). Approximately 53% of patients with PASH present with abnormalities on screening mammography, and 44% of patients with PASH present with palpable abnormalities. On imaging studies, PASH appears similar to fibroadenomas. On mammography, PASH is usually seen as a noncalcified, circumscribed mass. On ultrasound, PASH often appears as an oval, circumscribed, hypoechoic mass. On magnetic resonance imaging, PASH usually has progressive (Type 1) enhancement, and high-signal slit-like spaces may be seen on T2-weighted and short tau inversion recovery (STIR) images. The slit-like spaces correspond to empty clefts within acellular hyalinized stroma on histopathology. PASH may be mistaken for a low-grade angiosarcoma on pathologic examination. While angiosarcoma has true vascular spaces, PASH has a network of pseudoangiomatous slit-like clefts. Women with biopsy-proven PASH usually undergo follow-up imaging. Surgical excision may be considered for larger lesions and in women at an increased risk for developing breast cancer. In the future, additional studies are needed to provide definitive data regarding appropriate management and long-term outcomes for women with PASH. PASH has become increasingly recognized, but the literature regarding the imaging features of PASH is scarce. This paper reviews the imaging and pathologic features of PASH and some processes that may simulate PASH are discussed. Features of PASH on mammography, ultrasound, MRI, and nuclear medicine studies are discussed with pathologic correlation.