Synchronous Invasive Ductal Carcinoma of Breast and Diffuse Large B-cell Lymphoma: A Case Report.

Introduction: It is uncommon for breast cancer and non-Hodgkin lymphoma to present simultaneously. An increase in the rate of simultaneous malignancy identification has resulted from adopting more sensitive staging imaging techniques.

Case description: Here, we describe a patient who was diagnosed with axillary diffuse large B cell lymphoma (DLBCL) in a cancer hospital during a staging work-up for suspected breast cancer. Breast cancer was staged as Stage IIA and DLBCL as Stage IE. She was given three cycles of rituximab, cyclophosphamide, vincristine, doxorubicin, and prednisolone (R-CHOP) protocol. Interim positron emission tomography scan showed a complete metabolic response (Deauville score 2). She was given one more cycle of R-CHOP. Then, she had right breast-conserving surgery with axillary lymph node dissection in August 2023. Histopathology report showed residual disease with ductal carcinoma in situ. She was recommended weekly paclitaxel for 12 cycles and trastuzumab and pertuzumab for 1 year. She is currently having her adjuvant systemic therapy, after which she will be planned for local radiation. Endocrine treatment will be started once chemotherapy is completed.

Practical implications: Complete baseline work-up per standard protocols/guidelines should be done in each malignancy. Biopsy of metastatic sites should be done wherever possible. All histopathologies should be reviewed thoroughly before treatment initiation, as they may significantly alter patient management.