Eosinophilic “candy floss”-like inclusions in myeloma cells

Abstract

A 60-year-old female presented with weakness and pain in the bones that had persisted for 1 year. Radiological investigations revealed multiple lytic lesions in the skull and vertebrae. Abdominal ultrasound and computerized tomography did not reveal any lesions suggestive of solid organ malignancy. Serum protein electrophoresis revealed an ‘‘M’’ band in the gamma region. Tests of renal function and liver function were within normal limits. Complete blood counts showed anemia, with hemoglobin of 83 g/L. Bone marrow aspirate smears were hypercellular for age, with immature-looking plasma cells accounting for 55 % of all nucleated cells (top left). Myeloma cells were large, frequently bi- or multi-nucleate, and open chromatin with presence of nucleoli. Notably, many cells showed intracytoplasmic single large-round eosinophilic-amorphous inclusions, resembling cotton balls or ‘‘candy floss’’ (top right). In addition, many ‘‘flame cells’’ were also seen, with occasional flame cells exhibiting round inclusions (bottom left). The great majority of myeloma cells were immature with frequent presence of very large bizarre cells (bottom