Fibroadenoma is the most common breast tumor in women. Malignant transformation occurs rarely within fibroadenoma at older ages. Clinicians, radiologists, and pathologists need to be aware of malignant transformation within fibroadenomas. Radiologic studies play an important role in the diagnosis of fibroadenoma; however, radiologic findings are often nonspecific for malignancy and may appear completely benign. We detected an occult ductal carcinoma in situ that originated inside a fibroadenoma by using shear wave elastography. We report shear wave elastography findings of ductal carcinoma in situ within fibroadenoma and discuss the diagnostic role of this modality.