Introduction: Giant cell tumor (GCT) is an aggressive, but usually benign bone neoplasm most commonly arising in the metaphysis/epiphyses of long bones. While they are categorized as benign tumors, they can be locally aggressive and clinically have metastatic potential. The most common locations of this tumor include the distal femur, proximal tibia, and distal radius. We report a GCT arising in an atypical location and mimicking a breast mass.
Case presentation: This case was diagnosed at a large cancer center in Florida. Pertinent clinical findings were obtained from chart review and inter-departmental consultation. Radiologically, the initial impression included a deep-seated breast cancer with local chest wall invasion. Further evaluation revealed the mass to be an expansile rib lesion with extraosseous soft tissue invasion. Histological examination of the biopsy specimen showed bland multi-nucleated giant cells and mononuclear cells whose nuclei were morphologically similar. No necrosis, pleomorphism or mitotic activity was identified. No chondroid or osseous elements were present.
Conclusion: The histological features of bland mononuclear and multinucleated giant cells along with the lack of any additional mesenchymal elements led to the diagnosis of giant cell tumor. Resection of tumor was performed. The patient is disease free as of the last follow-up visit. This case is important as it shows where the physician must keep this diagnosis in mind whenever a deeply located breast mast is present.