<unk>  is a plasma cell dyscrasia in which a plasma cell tumour grows within soft tissue or within the axial skeleton. The International Myeloma Working Group lists three types: solitary<unk>  of bone (SPB); extramedullary<unk>  (EP), and multiple<unk> s that are either primary or recurrent. The most common of these is SPB, accounting for 3–5% of all plasma cell malignancies. SPBs occur as lytic lesions within the axial skeleton and extramedullary<unk> s most often occur in the upper respiratory tract (85%), but can occur in any soft tissue. Approximately half of all cases produce paraproteinemia. SPBs and extramedullary<unk> s are mostly treated with radiotherapy, but surgery is used in some cases of extramedullary<unk> . The skeletal forms frequently progress to multiple myeloma over the course of 2–4 years. Due to their cellular similarity,<unk> s have to be differentiated from multiple myeloma. For SPB and extramedullary<unk>  the distinction is the presence of only one lesion (either in bone or soft tissue), normal bone marrow (<5% plasma cells), normal skeletal survey, absent or low paraprotein and no end organ damage.
Plasmacytoma
Astrocytoma
Oligoastrocytoma
Retinoblastoma
Histiocytoma
Osteoblastoma
Pineocytoma
Ameloblastoma