Extramedullary involvement (or extramedullary disease, EMD) represents an aggressive form of multiple myeloma (MM), characterized by the ability of a clone and/or subclone to thrive and grow independent of the bone marrow microenvironment. Several different definitions of EMD have been used in the published literature. We advocate that true EMD is restricted to soft-tissue plasmacytomas that arise due to hematogenous spread and have no contact with bony structures. Typical sites of EMD vary according to the phase of MM. At diagnosis, EMD is typically found in skin and soft tissues; at relapse, typical sites involved include liver, kidneys, lymph nodes, central nervous system (CNS), breast, pleura, and pericardium. The reported incidence of EMD varies considerably, and differences in diagnostic approach between studies are likely to contribute to this variability. In patients with newly diagnosed MM, the reported incidence ranges from 0.5% to 4.8%, while in relapsed/refractory MM the reported incidence is 3.4 to 14%. Available data demonstrate that the prognosis is poor, and considerably worse than for MM without soft-tissue plasmacytomas. Among patients with plasmacytomas, those with EMD have poorer outcomes than those with paraskeletal involvement. CNS involvement is rare, but prognosis is even more dismal than for EMD in other locations, particularly if there is leptomeningeal involvement. Available data on treatment outcomes for EMD are derived almost entirely from retrospective studies. Some agents and combinations have shown a degree of efficacy but, as would be expected, this is less than in MM patients with no extramedullary involvement. The paucity of prospective studies makes it difficult to justify strong recommendations for any treatment approach. Prospective data from patients with clearly defined EMD are important for the optimal evaluation of treatment outcomes.
髓外浸润（或称髓外病变，EMD）是多发性骨髓瘤（MM）的一种侵袭性表现形式，其特征是克隆和/或亚克隆能够在骨髓微环境之外独立生存和生长。已发表的文献中对EMD存在多种不同的定义。我们认为真正的EMD仅限于因血行播散形成、且与骨结构无关联的软组织浆细胞瘤。EMD的典型发生部位随MM病程阶段而变化。诊断时，EMD通常见于皮肤和软组织；复发时，典型受累部位包括肝脏、肾脏、淋巴结、中枢神经系统（CNS）、乳腺、胸膜和心包。文献报道的EMD发病率差异显著，不同研究间的诊断方法差异可能是造成这种变异性的原因。在新诊断的MM患者中，报道的发病率为0.5%至4.8%，而在复发/难治性MM中报道的发病率为3.4%至14%。现有数据表明EMD预后不良，且明显差于不伴软组织浆细胞瘤的MM患者。在浆细胞瘤患者中，髓外浸润患者的预后比骨旁浸润患者更差。中枢神经系统受累较为罕见，但预后比其他部位的EMD更为严峻，若存在软脑膜浸润则预后尤差。目前关于EMD治疗效果的可用数据几乎完全来源于回顾性研究。某些药物和联合方案已显示出一定疗效，但正如预期，其效果不及无髓外浸润的MM患者。由于缺乏前瞻性研究，很难为任何治疗方案提出强有力的推荐建议。来自明确定义的EMD患者的前瞻性数据对于优化治疗效果评估至关重要。
Extramedullary disease in multiple myeloma: a systematic literature review
肿瘤(癌症)患者之家