Giant Vulvar Pseudoangiomatous Stromal Hyperplasia after Bilateral Breast and Axillary Lesions: A Delayed Multifocal Presentation

Abstract

Pseudoangiomatous stromal hyperplasia (PASH) is a benign myofibroblastic proliferation frequently encountered in the breast but rarely affects anogenital mammary-like glands, where it typically presents as small nodules. We report a rare case of a 38-year-old woman who developed a 95 × 60 × 60-mm vulvar mass 4 months after undergoing bilateral mastectomy and axillary excisions for histologically confirmed PASH. Pelvic MRI revealed a well-circumscribed, hypointense lesion in the posterolateral vaginal wall. Wide local excision was performed. Histopathology demonstrated a dense collagenous stroma with bland spindle cells forming interanastomosing slit-like, endothelial-free pseudovascular spaces, confirming the diagnosis of PASH. No fibroadenomatous component was observed. Immunohistochemical staining was positive for SMA and negative for CD31 and Factor VIII in the pseudovascular spaces, aiding in the exclusion of vascular neoplasms such as angiosarcoma. The patient remains recurrence-free at 1 year. This case highlights the potential for delayed multifocal PASH involving hormonally responsive anogenital sites, emphasizes its inclusion in the differential diagnosis of large vulvar masses, and underscores the need for surveillance of ectopic mammary-like tissues in patients with a history of PASH.