Giant cell tumor of the pubic bone with concomitant enchondroma: a case report.

Giant cell tumor of bone (GCTB) is a locally aggressive, intermediate-type neoplasm, accounting for approximately 4%-5% of primary bone tumors, typically arising in the metaphysis of long bones. Enchondroma is a common benign cartilaginous tumor, frequently localized in the short tubular bones of the hands and feet. The coexistence of these two distinct histopathological entities at the same anatomical site is exceedingly rare. We report a case of a 36-year-old female who presented with left hip pain after exertion for a duration of 2 weeks. Imaging studies revealed an osteolytic, expansile lesion in the left pubic bone, suggestive of GCTB. Histopathological examination of the resected specimen demonstrated two distinct morphological patterns: areas characteristic of GCTB (immunopositive for H3.3 G34W) coexisting with areas of enchondroma. This coexistence is exceptionally uncommon in bone tumors, particularly at the pubic location. Notably, the GCTB component exhibited extraosseous soft tissue extension and identifiable intravascular tumor thrombi, with a Ki-67 proliferation index reaching 40%, indicating a high aggressive potential. Corroborated by a review of the literature, this case emphasizes the critical role of histopathological evaluation in diagnosing bone tumors and discusses the diagnostic approach and clinical implications of such a rare tumor combination.