OBJECTIVETo study the clinicopathologic features of metastatic carcinoma in bone and to evaluate the role of immunohistochemistry in delineation of possible primary sites.

METHODSOne hundred and forty-one cases of metastatic carcinoma in bone encountered during the period from 1998 to 2004 in People's Hospital, Peking University, were reviewed retrospectively. The clinical information, radiographic features and pathologic findings were analyzed. Immunohistochemical study for antigens including cytokeratins, prostatic specific antigen, thyroglobulin, thyroid transcription factor 1 and gross cystic disease fluid protein 15, was performed in 51 cases possessing skeletal metastasis with unknown primary.

RESULTSSkeletal metastasis occurred more commonly in males (male to female ratio = 1.7:1). The age of patients ranged from 23 to 86 years (mean age = 56.5). The presenting symptoms included pain and dysfunction in the affected bones. The locations of skeletal metastasis were as follows: spine (58), pelvic bone (46), long bone (34) and others (3). Twenty-three cases harbored multiple bony lesions. Radiographically, 99 cases (70.2%) of skeletal metastasis were detected by X-rays, including 85 cases (85.9%) showing lytic changes. The primary sites of the tumor could be determined by clinicopathologic correlation in 90 cases (63.8%) and were unknown in the remaining 51 cases. Upon immunohistochemical study, the primary sites were determined in another 40 cases. Overall, the primary sites were identified in 130 cases (92.2%), which included lung (37), female genital system and breast (25), kidney (18), gastrointestinal system (17), liver (12), thyroid (11), prostate (7), bladder (2) and skin (1).

CONCLUSIONSSkeletal metastasis occurs more often in elderly males. Axial bones (spine and pelvis) are usually affected. Lung and female genital system are frequent the primary sites. Immunohistochemical study is useful in cases with occult primary.