1944—1969年Kansas大学医学中心21000肿瘤登记病例记录中,686例原发灶部位不明,占3.2％;各组年龄均有发现,30岁以前者少见,75％患者诊断时年龄在50—80岁间,平均60.2岁;男性与女性之比为58∶42。表Ⅰ列举可供分析的617例转移的主要部位,常见顺序为骨、肺、肝、全身性癌病、中枢神经系统、腹部癌病和颈部淋巴结。 From 1944 to 1969, at the Kansas University Medical Center 21,000 tumor registry records, 686 primary tumor sites were unknown, accounting for 3.2%; ages were found in all groups, rare before 30 years of age, and 75% of patients diagnosed at age 50-80. The average age was 60.2 years; the ratio of male to female was 58:42. Table I lists the major sites of 617 metastases that can be analyzed. The common sequence is bone, lung, liver, systemic cancer, central nervous system, abdominal cancer, and cervical lymph nodes.