Primary mediastinal giant cell tumors: a clinicopathologic and immunohistochemical study of two cases

Two cases of posterior mediastinal giant cell tumors are presented. The patients are a woman and a man, 31 and 18 years old, respectively. One of the patients had symptoms of paresthesias while the other was completely asymptomatic. Complete physical examination did not disclose evidence of tumor elsewhere. Neither patient had a previous history of malignancy. Surgical resection was performed. Histologically, both tumors were composed of a proliferation of osteoclast-like giant cells associated with a mononuclear cell population composed of oval and spindle cells. Mitotic activity and mild cellular atypia were present in the mononuclear cell component. No evidence of necrosis or hemorrhage could be demonstrated in either case. Immunohistochemically, both tumors showed strong positive reaction in the mononuclear component for antibodies against vimentin and CD68, while keratin, epithelial membrane antigen, CD45, S-100 protein, and desmin were negative. On clinical follow-up, both patients are alive and well without evidence of recurrence or metastasis 6 and 108 months after surgery. The present cases highlight the ubiquitous distribution of soft tissue giant cell tumors and the importance of considering these tumors in the differential diagnosis of posterior mediastinal neoplasms.