This article is an answer to the Case – Painless, Nickel-Sized Lump on the Scalp
A computed tomographic scan showed a destructive, well-demarcated, soft-tissue mass, with peripheral bony fragments, emerging from the right frontal calvarium. The mass measured 5 cm by 4 cm and was compressing part of the brain. There was no evidence of a midline shift. The mass was excised, and cranial mesh placed over the calvarial deficit.
Histologic examination revealed a plasmacytoma of bone with extensive amyloidosis. Examination of a bone-marrow–biopsy specimen showed 20% plasma cells, and a skeletal survey revealed multiple lytic lesions of the long bones and skull. No monoclonal proteins were found on electrophoresis or immunofixation of the serum or urine.
The patient was given a diagnosis of nonsecretory multiple myeloma. As is common in such cases, the more sensitive free-light-chain assay revealed a pathologically elevated concentration of kappa light chains in the serum. In this patient, nonspecific proteinuria developed, although renal function remained unimpaired.
She has now undergone autologous bone marrow transplantation, with no evidence of disease recurrence on follow-up bone marrow biopsy or laboratory studies.
