56-year-old male with left-sided weakness

Area of Science:

• Neuro-oncology
• Hematology
• Pathology

Background:

• Multiple myeloma (MM) is a plasma cell malignancy typically affecting the bone marrow.
• Intraparenchymal brain involvement by MM is rare, often presenting as leptomeningeal disease or solitary plasmacytomas.
• Previous treatments for MM include autologous stem cell transplantation.

Observation:

• A 56-year-old male with treated multiple myeloma presented with hemiparesis and ataxia.
• Brain MRI revealed a large, enhancing frontoparietal lesion with unusual T2WI characteristics, initially suspected to be a high-grade glioma.
• Surgical resection was performed for diagnosis and treatment.

Findings:

• Pathology confirmed the lesion was a relapse of multiple myeloma, characterized by CD138 positive plasma cells.
• The specimen showed an unusual histological pattern with neoplastic cells in a proteinaceous background.
• Immunophenotype analysis confirmed a monoclonal plasma cell population identical to the initial diagnosis.

Implications:

• This case highlights an extraordinary intraparenchymal presentation of multiple myeloma relapse.
• The unusual radiographic and histological features underscore the diverse manifestations of MM.
• Further investigation is needed to determine the nature of the proteinaceous background substance.