Pseudoangiomatous stromal hyperplasia of the breast in a 10-year-old girl.

Pseudoangiomatous stromal hyperplasia (PASH) of the breast is a benign lesion, characterized by a dense proliferation of stromal mesenchymal cells of myofibroblastic origin forming empty, slitlike channels. The development of PASH is subject to hormonal influence and is most commonly seen in premenopausal women. In adolescent patients, PASH is rarely reported. Here we report a case of PASH presenting in a 10-year-old girl. After the presentation and inconclusive radiographic findings, incisional biopsy revealed a soft nodule with histopathologic features characteristic of PASH. Immunoperoxidase studies showed positive immunoreactivity for CD34 and bcl-2 and negative immunoreactivity for CD31 and desmin, supporting the diagnosis of PASH. Because of the benign nature of the lesion, excisional biopsy was deferred to minimize damage to the patient's developing breast. To our knowledge, this case represents the youngest female patient with unequivocal PASH in reported literature.