Massive nodular pseudoangiomatous stromal hyperplasia (PASH) of the breast arising simultaneously in the axilla and vulva

The authors describe a 52-year-old woman with a history of bilateral mastectomies for macromastia caused by massive nodular pseudoangiomatous stromal hyperplasia (PASH), who presented with 2 large growths in her left axilla and groin. These masses had been increasing in size for nearly a year. When excised, the axillary mass had dimensions of 14.0 × 14.0 × 5.5 cm ³ and weighed 664 g. The groin mass was slightly smaller at 14.5 × 11.0 × 5.0 cm³ and 518 g. Microscopic examination of both masses revealed breast tissue expanded by a hyalinized stroma with prominent slit-like pseudovascular spaces, consistent with PASH. Small incidental foci of PASH are common findings in breast excisions; however, large nodular foci are rare. Furthermore, nodular foci in accessory breast tissue are exceedingly rarer and can raise clinical concerns for malignancy. Histopathologically, PASH can be mistaken for low-grade angiosarcoma. To the authors' knowledge, the present case appears to be the first description of multiple simultaneous foci of massive nodular PASH arising in accessory breast tissue.