Development of an Invasive Ductal Carcinoma Within a Complex Fibroadenoma

Abstract

Fibroadenomas (FAs) are among the most common benign tumors of the female breast with peak incidence in the second and third decade of life. Fibroadenomas are generally not considered premalignant and are not reported as an independent risk marker for breast cancer. Carcinoma in situ may occasionally be present within an FA, and invasive cancer originating in the surroundings may be observed to extend into an FA. Cancer arising within an FA is, however, unusual with a reported incidence ranging from 0.02% to 0.125% and fewer than 250 reported cases. Complex FAs have been associated with a higher relative risk of developing breast cancer, but this may be related to the presence of associated benign proliferative changes. We present a case of invasive ductal carcinoma arising within a complex FA in a 56-year-old woman with a growing lump in the upper lateral quadrant of the right breast. The lump had been present for 20 years and was classified as a benign lesion by mammography and verified by several biopsies. The patient underwent lumpectomy, and histopathologic examination incidentally showed a 27-mm invasive ductal carcinoma completely encapsuled within a complex FA. The patient subsequently underwent sentinel node procedure without sign of metastasis. Fibroadenomas are not associated with an increased risk of breast cancer but may rarely be involved with malignancy. The presented case illustrates that detection of premalignant and/or malignant changes within an FA may be delayed because of benign radiological and clinical findings.