My mom has plasmacytoma in the right left(upper tibia). could this be multiple myaloma?

They are related: Plasmacytoma is a localized form of multiple myeloma. When we look and search deeply, many such patients already have some evidence of systemic disease(Multiple myeloma). But some cases are truly localized to one spot in which case they can be cured with local Radiotherapy(and may be bale to avoid taking chemotherapy, which is standard treatment for disseminated disease.

Plasmacytoma: Having 2 plasmacytomas in long bones is considered as one of the major criteria for myeloma. She needs complete staging workup which might have been done already and should include cbc, chemistry panel, immunoglobulin levels. Spep, ife. 24 hour urine for protein, serum light chain assay, beta 2 micro globulin and a bone marrow biopsy aspirate and biopsy with cytogenetic a and fish panel.