PLASMA CELL NEOPLASM IN BREAST: A RARE CASE REPORT

Abstract Introduction/Objective Breast carcinoma continues to be the most common malignancy in women however plasma cell neoplasms are rare in breast tissue. Most of these recorded cases are from patients with Multiple myeloma (1). We present a rare case of a new breast lesion in a 69 year female incidentally found on imaging. She had a history of adenocarcinoma of lung with brain metastasis undergoing treatment. Methods/Case Report The patient’s breast lesion presentation was unusual without any pain or associated symptoms, but a new right breast mass was incidentally discovered on CT-Chest Abdomen-Pelvis. Mammogram revealed a 1.4 cm circumscribed mass in lower, outer breast with scattered calcifications. With the suspicion for a primary breast malignancy or metastatic disease from her lung cancer the patient’s breast lesion was biopsied. On histology, abnormal proliferation of cells with ovoid nuclei, vesicular chromatin and variable cytoplasm was noted with a background of mature adipose tissue. Immunohistochemistry showed neoplastic cells positive for plasma cell associated markers including CD38 (patchy), CD56, CD138, and MUM1 with a kappa restriction on ISH. The Ki67 showed 20% proliferation index. EBER was negative and SMARC4 and INI were preserved. Other immunohistochemical stains were performed to rule out differentials and were all negative. The morphology and IHCs were consistent with the diagnosis of Plasma cell neoplasm with kappa-restriction. Subsequently this patient developed a shoulder lesion which on biopsy showed a plasma cell neoplasm expressing plasma cell markers and kappa light chain overexpression. Results (if a Case Study enter NA) NA Conclusion It is critical to distinguish a breast plasma cell neoplasm from other primary and metastatic breast lesions in order to avoid unnecessary surgery and cytotoxic chemotherapy. Rarely, plasma cell neoplasm can manifests as a breast lesion, which in this case turned out to be the early manifestation of multiple myeloma.