Background/objectives: Despite advancements in early diagnosis and clinical practices guided by standardized care protocols, Merkel cell carcinoma (MCC) is marked by an unfavorable prognosis with a 5-year relative survival rate of 65%, based primarily on data collected prior to the introduction of immunotherapy. Regional nodal metastases affect 40–50% of MCC patients, while approximately 33% experience distant dissemination. Among these, bone and bone marrow metastases are particularly notable, although the characteristics and clinical implications of this metastatic disease in MCC remain poorly understood. Methods: A comprehensive review was conducted using the Medline database (via PubMed) up to January 2025. The search strategy included the string “(Merkel cell carcinoma AND (bone OR marrow))”. Results: A total of 1133 (69.3% male and 30.7% female) patients diagnosed with advanced MCC were collected. The median (IQR) age at diagnosis was 67.5 (12.65) years old. Overall, 201 (20.8%) cases of bone and/or bone marrow metastases were identified and linked to a primary known MCC in 75.7% of cases. Bone metastases (BMs) appear as the third most common metastatic site, following the liver (second) and lymph nodes (first). They show mixed biological and radiological behavior, with a marked preference for the axial skeleton over the appendicular one. Addressing the characteristics of metastatic bone disease, neurological symptoms were the most documented, whereas bone marrow involvement and leukemic spread seemed to be primarily related to immunosuppression. Multimodal treatment strategies, including platinum-based chemotherapy and radiotherapy, were the primary approaches adopted, reflecting therapeutic practices from the pre-immunotherapy era. Conclusions: The pattern of metastatic spread in MCC differs among studies, with the bones resulting as the third most common site of distant spread. Excluding head and neck MCC, which seems to be more regularly associated with liver metastases, the relationship between the primary tumor site and the development of bone or bone marrow metastases appears inconsistent. Overall, BMs mostly correlated with advanced MCC stages and poorer survival outcomes, with a median overall survival (OS) of 8 months (range 12.75–4). The integration of international guidelines, evolving evidence from clinical trials, and the expanding role of immune checkpoint inhibitors (ICIs) will contribute to improving systemic disease control and enhance patient care.
背景/目的：尽管早期诊断和基于标准化诊疗方案的临床实践已取得进展，默克尔细胞癌（MCC）的预后仍不理想，基于免疫治疗应用前数据统计的5年相对生存率仅为65%。区域淋巴结转移影响40-50%的MCC患者，约33%发生远处播散。其中骨与骨髓转移尤为显著，但此类转移性病变的特征及临床意义尚不明确。方法：通过Medline数据库（经由PubMed）对截至2025年1月的文献进行系统性综述，检索策略采用“（默克尔细胞癌 AND（骨 OR 骨髓））”组合检索式。结果：共纳入1133例晚期MCC确诊患者（男性占69.3%，女性占30.7%），诊断中位年龄（四分位距）为67.5（12.65）岁。共发现201例（20.8%）骨和/或骨髓转移病例，其中75.7%与已知原发性MCC相关。骨转移（BMs）位列第三常见转移部位，仅次于肝脏（第二位）和淋巴结（第一位）。其生物学与影像学表现呈混合性特征，明显好发于中轴骨而非附肢骨。在转移性骨病特征方面，神经系统症状记录最为常见，而骨髓受累与白血病样播散主要与免疫抑制相关。以铂类化疗和放疗为主的多模式治疗策略是主要治疗手段，反映了免疫治疗时代前的临床实践。结论：不同研究中MCC转移模式存在差异，骨转移位列第三常见远处转移部位。除头颈部MCC更常与肝转移相关外，原发肿瘤部位与骨/骨髓转移发生的关系尚不一致。总体而言，骨转移多与晚期MCC分期及较差生存结局相关，中位总生存期（OS）为8个月（范围12.75-4）。国际指南的整合、临床试验证据的积累以及免疫检查点抑制剂（ICIs）应用的拓展，将有助于提升全身性疾病控制水平并改善患者诊疗。
Merkel Cell Carcinoma: An Updated Review Focused on Bone and Bone Marrow Metastases
肿瘤(癌症)患者之家