Pseudoangiomatous stromal hyperplasia tumors are rare. In this retrospective study, we evaluated the clinical, radiologic, and pathologic features of pseudoangiomatous stromal hyperplasia tumors and compared histologic findings of pseudoangiomatous stromal hyperplasia tumors with clinical outcome. We identified 26 patients (mean age, 47 years) with pseudoangiomatous stromal hyperplasia tumors who had been diagnosed at our institution. Sixteen patients (62%) were premenopausal, and 13 (50%) had a history of oral contraceptive or hormone replacement therapy use. Ten patients (38%) presented with a palpable mass; in the other patients, the tumors were detected by mammography (where it usually appeared as a hyperdense mass with irregular margins) or sonography (where it usually appeared as a hypoechoic mass). Lesions were a mean of 4.2 cm at the largest dimension (range, 0.8-11 cm). Histologically, pseudoangiomatous stromal hyperplasia was classified as simple in 18 patients (69%) and fascicular/proliferative in eight patients (31%). In one patient (4%), an invasive ductal carcinoma was present within the pseudoangiomatous stromal hyperplasia tumor. We found associated benign epithelial lesions in eight patients (31%) and/or gynecomastia-like changes in 17 patients (65%). The presence of gynecomastia-like changes was significantly associated with intralobular location of pseudoangiomatous stromal hyperplasia (P=0.00085, by Fisher's exact test). Follow-up data were available for 15 patients (mean +/- s.d., < or =27 +/- 17 months). No additional pathology or substantial changes in existing lesions were found on imaging. All pseudoangiomatous stromal hyperplasia tumors diagnosed by core needle biopsy but not subsequently excised remained clinically and radiologically stable; therefore, offering the option of close clinical surveillance instead of surgery in patients with pseudoangiomatous stromal hyperplasia tumors diagnosed by core needle biopsy in selected patients.