Giant cell tumor of soft tissue is a rare tumor, which demonstrates a spectrum of benign to malignant characteristics. Microscopically, these tumors are composed of multinucleated giant cells evenly dispersed among mononuclear cells, and are histologically indistinguishable from their bone equivalent.2
In 1972, Salm and Sissons were the first to describe a series of 10 patients with giant cell tumors of soft tissue.1
In their study, the tumors demonstrated benign features without metastases. However, there was local recurrence in two patients. In the same year, Guccion and Enzinger reported a series of 32 patients with soft tissue tumors similar to those studied by Salm and Sissons, but with malignant features and widespread metastases.3
These tumors were called “malignant giant cell tumors of soft parts.” In 2000, O'Connell et al.
described a series of 18 patients with giant cell tumors of soft tissue that demonstrated a spectrum from benign to malignant behavior determined by the cytological appearance of the mononuclear cells and mitotic activity.5
Giant cell tumors of soft tissue can be seen at any age, but usually affect middle-aged adults of both sexes. These tumors can occur in both the superficial and deep soft tissues. The majority of these tumors reported in the literature have been located in the lower extremity, particularly in the thigh.2,3
Other sites of involvement include the upper extremities, trunk, and rarely the skin.6
The most common clinical presentation is a painless soft tissue mass.5
In a series of 22 patients with giant cell tumor of soft tissue, Oliveira et al.2
described the recurrence rate to be 6.2%, which was less than the 25% reported recurrence rate of giant cell tumors of bone.1
However, the metastatic and death rates were determined to be higher in giant cell tumors of soft tissue.1
Immunohistochemically, the giant cell tumor of soft tissue in this case report expressed CD68 and CD34. Conversely, the giant cell tumors of soft tissue reported in the literature expressed only CD68.
This case report illustrates a primary giant cell tumor of soft tissue located within the posterior mediastinum. The only other report of a primary mediastinal giant cell tumor of soft tissue in the English literature was published by Fu et al.
in 2002, in which they described two patients with posterior mediastinal masses.4
Our case is very similar to those described by Fu et al.
, as the cells all had low mitotic activity and the patients had a favorable clinical course without metastases or recurrence of the tumor.
In conclusion, giant cell tumors of soft tissue are rare tumors that demonstrate a spectrum of benign to malignant potential. Although the majority of these tumors are located in the lower extremity, they may occur rarely in the posterior mediastinum and present as a posterior mediastinal mass.