Background: Fibroadenoma is the most common benign breast tumor. However, the coexistence of ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) within single breast fibroadenomas is rare.
Case description: A 71-year-old woman presented with a palpable mass in her left breast, and she had a history of right-side breast cancer, which had been treated 16 years ago. Invasive ductal carcinoma was confirmed through core needle biopsy. She subsequently underwent left breast mastectomy with sentinel lymph node biopsy. Postoperative pathological examination revealed two fibroadenomas: the larger one coexisted with IDC and focal DCIS, and the small one coexisted with high-grade DCIS. Immunohistochemical analysis showed positive expression of estrogen receptor (ER) and progesterone receptor (PR), but negative expression of Her-2, demonstrating a Luminal B1 subtype (clinical stage IA). She had completed the adjuvant chemotherapy and currently received endocrine therapy. No recurrence was found during the follow-up examinations.
Conclusion: Coexistence of fibroadenoma, DCIS and IDC in unilateral breast mass is rare, highlighting the importance of comprehensive preoperative evaluation, optimal surgical strategy and accurate histopathological examination.
Keywords: breast fibroadenoma; case report; coexistence; ductal carcinoma in situ; invasive ductal carcinoma.
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