Imaging findings for malignancy-mimicking nodular fasciitis of the breast and a review of previous imaging studies
A 41-year-old woman visited our hospital with the chief complaint of a palpable mass in her left breast, which she had noticed 1 week prior. There was no history of trauma or family history of breast cancer. A mammogram showed a 10-mm oval isodense mass in the upper center of the left breast with a partially indistinct margin (), which was newly developed in comparison with her last mammogram 6 years ago. Ultrasonography revealed an 8 × 11 mm, irregular, hypoechoic, microlobulated mass with echogenic halo () at the 12 o’clock position of the left breast. This finding was suspicious of malignancy; therefore, she underwent an ultrasound-guided core needle biopsy.\nHistologically the lesion had an ill-defined proliferation of short spindle cells admixed with occasional giant cells. Nodular fasciitis or spindle cell carcinoma was ruled out.\nExcisional biopsy was done for further evaluation. Histopathology of excisional biopsy showed nodular proliferations of short spindle cells and occasional giant cells with dense collagenous stroma and surrounding chronic inflammatory cells, consistent with nodular fasciitis ().