Invasive lobular breast cancer with dense lymphocytic infiltration treated with surgery, radiation, chemotherapy, and endocrine therapy

What happened, in summary

This 66-year-old Japanese woman was referred after screening found a high-density mass in the upper-inner quadrant of her right breast. Ultrasound showed an irregular 2.7 × 1.6 cm hypoechoic mass, while CT and MRI found no evidence of distant metastasis or lymph-node involvement. A core needle biopsy was difficult to interpret because small lymphocytes densely infiltrated the breast tissue, raising the possibility of breast cancer, a reactive lymphoid lesion, or low-grade lymphoma. Because the diagnosis remained unclear, she underwent lumpectomy/excisional biopsy with a wide surgical margin. Pathology showed invasive lobular carcinoma in a background of dense lymphocytic infiltration, with loss of E-cadherin. The tumor was ER-positive in more than 95% of cells, PgR-negative, HER2 1+, and Ki-67 35%, consistent with a luminal B subtype. Sentinel lymph-node biopsy found no axillary nodal metastasis, surgical margins were negative, and the final stage was pT2N0M0, Stage IIA. She received adjuvant whole-breast irradiation. Because the Oncotype DX recurrence score was 28, she also received adjuvant epirubicin plus cyclophosphamide followed by docetaxel. She then began aromatase inhibitor endocrine therapy as a postmenopausal patient. At 1 year after surgery, she remained recurrence-free. Her workup also showed no swollen axillary or supraclavicular nodes, no lymphoma-type B symptoms, and tumor markers within the reported reference ranges. Mammography categorized the mass as suspicious, and MRI suggested possible intraductal spread toward the nipple. Those details mattered because the original biopsy had looked partly lymphoid, but the surgical specimen clarified that the dominant process was breast carcinoma rather than lymphoma.