A Case of Breast Cancer with a Peculiar Invasive Pattern within a Fibroadenoma

Abstract

A 59-year-old woman was referred to our department because a follow-up PET-CT scan after treatment for malignant lymphoma showed an abnormal FDG uptake within a known fibroadenoma (FA). When she was first seen, a tumor about 4cm in diameter was palpated in the AC area of the right breast. Mammography showed a known FA in the same area and heterogeneous calcifications in its medial dorsal area. Ultrasonography of the breast showed a known FA and a hypoechoic mass which was irregular in shape inside of the FA. Core needle biopsy was performed for both lesions and diagnosed as invasive ductal carcinoma inside of the FA and partial invasion of cancer in it. Contrast-enhanced MRI of the breast showed an irregular mass with uneven contrast effects inside of the FA and strong contrast effects along the margins and internal septum of the FA, and we confirmed the spread of the lesion. We performed right mastectomy and sentinel lymph node biopsy. Pathological examination revealed an invasive ductal carcinoma scirrhous type which was adjacent to and invaded the fibroadenoma. It was peculiar to have invaded the sparse interstitial area predominantly surrounding the FA nodule.