A case of nodular pseudoangiomatous stromal hyperplasia (PASH)

Pseudoangiomatous stromal hyperplasia (PASH) of the breast is a common microscopic lesion that is found at breast biopsy, and presents with proliferation of the stromal cells and slit-like pseudovascular spaces with endothelial-like spindle cells. In contrast, nodular PASH is relatively rare. We report here a case of nodular PASH with multiple palpable masses. A 49-year-old woman who had experienced gradual enlargement of her breasts for 13 years noticed an elastic but firm palpable mass in her breast. We were able to detect 7 masses in her right breast and 2 in the left. Ultrasonography and mammography demonstrated nonspecific findings, and FNA and CNB did not establish a diagnosis. An excisional biopsy was performed, and the pathological findings revealed nodular PASH. Eighteen months after the excisional biopsy, the size of the nodules and the whole breast had decreased remarkably. While the possibility of a change in the hormonal background or the influence of drugs was considered, we were not able to reach a single specific conclusion regarding the pathogenesis.