Bone metastases: A compilation of 365 histologically verified cases spanning over two decades from a single center.

Objective: To analyze the clinicopathological features of metastatic bone tumors over a period of two decades and identify the primary site of malignancy in metastasis of unknown origin. Materials and Methods: A total number of 365 cases were included in the study. The clinical features and location of the tumors were noted. The histopathological features of all the cases were studied. Immunohistochemistry (IHC) was done either to categorize or confirm the primary diagnosis using organ specific/organ restricted markers. Results: A total 712 bony sites were involved by metastasis in 365 patients, of which spine was the most commonly affected. Metastasis was the initial presentation in 69.5% patients. The primary site was known in 220 patients and almost half of them were detected after the diagnosis of metastasis. IHC was used as adjunct to suggest the possible origin in cases with unknown primary in 27.4%. Among the metastatic carcinoma, adenocarcinoma was the most common histological subtype with thyroid being the most frequent primary site of origin followed by lung and breast. Conclusion: More than two-third of cases in surgical pathology practice present as initial manifestations. Detection rate of primary depends on extent of metastatic work-up and IHC with organ specific/organ restricted markers to facilitate treatment with bone targeting agents.