Solitary plasmacytoma is plasma cell neoplasm. It is a localized bone disease and for this reason it is different from multiple myeloma (systemic plasma cell neoplasm). Sometimes, solitary plasmacytoma precedes a following multiple myeloma. Clinical findings of solitary plasmacytoma are related to the univocal localization on damaged bone, while laboratory findings could be similar to multiple myeloma (i.e. M component, kidney dysfunction, blood calcium alterations, increased beta-2-microglobulin). However, during a solitary plasmacytoma, laboratory findings could not be present contemporaneously such clinical complications (i.e. kidney failure, immunological disorders with a trend toward infectious disease and/or autoimmunity, neurological disorders, haematological disorders, amyloidosis, POEMS syndrome). These raise the reason because solitary plasmacytoma has better prognosis compared to multiple myeloma.