Tenosynovial Giant Cell Tumor With Bone Erosion of the Tibial Midshaft

Case: A 37-year-old woman presented with a 2-week history of a palpable leg mass. Radiographs revealed a 7-mm focal cortical lytic lesion in the midmedial tibial diaphysis with adjacent soft-tissue component. MRI confirmed soft-tissue mass with cortical erosion. Biopsy established a localized type tenosynovial giant cell tumor (TGCT). En bloc excision of the 3-cm mass was performed. Histopathology confirmed localized type TGCT with cortical erosion. The patient remained asymptomatic at the 1-year follow-up without recurrence. Conclusion: This rare presentation with midshaft tibial erosion highlights that TGCT should remain in the differential diagnosis even for apparent primary bone lesions in unusual nonperiarticular locations.