Primary giant cell tumor of soft tissues similar to bone giant cell tumor: A case report and literature review.

In this report we describe a primary giant cell tumor (GCT) of soft tissues located in the left dorsal wrist of a 52-year-old man. Plain radiographs did not reveal any lesion in his carpal or hand bones. Although the tumor was clinically considered a ganglion initially, the microscopic features were identical to those found in classic GCT of bone. Light microscopy showed a lesion composed of a homogeneously mixed proliferation of spindle and polygonal mononucleated stromal cells and evenly distributed multinucleated, osteoclast-like giant cells. Whereas most bone tumors have an extraosseous counterpart, only 13 cases of GCT in soft tissues had been published until 1998. Moreover, 64 new cases have been reported in three series. Nevertheless, most major reviews and textbooks do not consider this tumor as a specific entity and regard it as a low grade variant of malignant GCT of soft tissue. We describe the clinical, histologic, and immunohistochemical features of this rare benign neoplasm emphasizing the differential diagnosis with its malignant soft tissue counterpart, an ominous tumor.