Abstract
Nodular fasciitis is a reactive proliferative lesion of fibroblast cells ; it occurs most commonly in the limbs, particularly the forearms. Cases involving the breast and the chest wall are rare. We treated 1 case of nodular fasciitis involving the pectoral muscles that spontaneously regressed with no treatment. A 74-year-old woman noticed a mass in her left breast ; a mass approximately 3 cm in size could be felt in the superolateral area of the left breast. On ultrasound, a poorly-marginated, hypoechoic mass approximately 3.6 cm in size was noted in the left mammary gland C region ; on needle biopsy, nodular fasciitis was strongly suspected. However, it was difficult to differentiate from a malignant tumor. Thus, an excisional biopsy was required to make a definitive diagnosis. On the day of biopsy, approximately 1 week later, the tumor had spontaneously regressed and was no longer present.
