The need for bone biopsies in the diagnosis of new bone lesions in patients with a known primary malignancy: A comparative review of 117 biopsy cases.

OBJECTIVE: This study used a clinical dataset to investigate the proportion of the newly found bone lesions in malignant patients diagnosed by biopsy as being benign, malignant but unrelated to the primary malignancy, or bone metastases of the primary malignancy. The clinical factors that might affect the correlation between bone lesions and the primary malignancy were also analyzed. It is expected to obtain some information contributing to the clinical decision-making regarding the need for biopsy of these lesions from the research results.

METHODS: Data from patients with a single known malignant tumor who had undergone biopsy of newly found bone lesions at our research institution between January 2012 and December 2017 were reviewed. Based on the pathology results, included cases were divided into a bone-metastasis-of-primary-tumor group (Group 1) and a non-bone-metastasis-of-primary-tumor group (Group 2). The sex, age, diagnostic interval time between the primary malignancy and bone lesions, clinical symptoms, number of involved bones, sites of bone biopsy, and 18 F-FDG PET/CT results were compared between groups.

RESULTS: A total of 117 patients (92 in Group 1 and 25 in Group 2) were included in the study. There was no significant difference in the sex, age or diagnostic interval time between patient groups. Of all the cases, 17.9% (21/117) were identified to be benign lesions such as fibrous dysplasia ( n  = 2), bone tuberculosis ( n  = 1), simple bone cyst ( n  = 1), aneurysmal bone cyst ( n  = 1), or solitary fibrous tumor ( n  = 1). Meanwhile, 3.4% (4/117) were new malignancies including chondrosarcoma ( n  = 1), plasmacytoma ( n  = 1) and bone metastases unrelated to the primary malignancy ( n  = 2). Bone metastases pertinent to the primary tumor accounted for 78.6% (92/117) of cases. Liver ( n  = 18), kidney ( n  = 14), breast ( n  = 13) and lung ( n  = 12) were the most common cancers among cases. Cases with clinical symptoms exhibited a higher likelihood of their bone lesions being diagnosed as bone metastases of their primary malignancy than those without clinical symptoms (81.3% (87/107) vs. 50.0% (5/10)) ( P  = 0.021). Neither the number of bone lesions nor the biopsy sites appeared to influence whether the bone lesions were metastases of the primary malignancy or not. In PET/CT examination, the mean maximum standardized uptake values of the two groups were similar.

CONCLUSIONS: This study indicated that more than 1/5 of newly identified bone lesions in patients with a single known malignancy were not clinically associated with their primary tumors. Furthermore, 3.4% of these were newly discovered malignant bone tumors. The presence of clinical symptoms may be a significant factor affecting whether a new bone lesion is clinically linked to a patient's primary malignancy. Based on the experience from these patients, as for the newly found bone lesions, it is worthy to perform an active biopsy on those asymptomatic ones to avoid misdiagnosis and less biopsy on symptomatic ones for the sake of less cost and risks.