Soft tissue plasmacytomas are classified into primary or secondary. Primary soft-tissue plasmacytomas predominantly occur in the head and neck region. When there is no bone marrow involvement, the prognosis is favorable. Genetically, they are primarily characterized by 1q amplification and del(13q). The preferred treatment is local radiotherapy or surgical excision; for extensive lymph node involvement, bortezomib is administered. Secondary soft-tissue plasmacytomas are typically seen in relapsed multiple myeloma, with a shorter survival time. They frequently harbor high-risk mutations such as del(17p) and t(4;14), requiring multi-agent intensive therapy and/or autologous hematopoietic stem cell transplantation. The prognosis of soft-tissue plasmacytomas is influenced by genetic alterations and affected anatomical sites. Future research should focus on targeting drug-resistance mechanisms and establishing diagnostic-therapeutic protocols.