Aggressive multiple myeloma with lymph node involvement, loss of CD138, and adipophilin-positive cytoplasmic...

We describe a rare and aggressive case of multiple myeloma (MM) characterized by extensive lymph node involvement, loss of CD138 expression, and adipophilin (ADP)-positive cytoplasmic vacuolization, highlighting the role of lipid metabolism in disease aggressiveness. An 83-year-old woman presented with painless cervical lymphadenopathy and widespread osteolytic lesions. Bone marrow examination confirmed MM, while lymph node biopsy showed diffuse infiltration of atypical lymphoid cells with numerous tingible body macrophages, initially mimicking a high-grade lymphoma. Immunophenotyping showed CD3/CD5/CD20/CD23 negativity, focal CD138/CD79a positivity, diffuse MUM1 and κ-light chain positivity, and a high Ki-67 index. Compared with bone marrow plasma cells, lymph node MM cells exhibited prominent cytoplasmic vacuoles and nuclear enlargement. Immunohistochemistry demonstrated ADP positivity in lymph node lesions but not in bone marrow MM cells, suggesting metabolic reprogramming toward lipid utilization. Despite anti-myeloma therapy, the disease rapidly progressed, and the patient died within two months. This case underscores the clinical significance of CD138 down-regulation as a marker of dedifferentiation and poor prognosis, and suggests that altered lipid metabolism may contribute to the aggressiveness of metastatic MM. To the best of our knowledge, this is the first MM case with lymph node involvement showing CD138 down-regulation and ADP positivity.