Unusual aggressive course of a giant cell tumor of soft tissue during immunosuppressive therapy.

Giant cell tumor of soft tissue with low malignant potential (GCT-ST) is a low-grade, primary soft tissue sarcoma with histological and clinical features similar to giant cell tumor of the bone. The main tumor localizations are the extremities, but it may also occur in the head and neck region. GCT-ST shows a recurrence rate of approximately 15%, but it very rarely metastasizes. The risk of cancer development, especially of the skin, is up to fivefold increased in immunosuppressed patients after organ transplantation. The association of sarcomas and immunosuppressive therapy is best known for Kaposi sarcomas, whereas other types of sarcomas are rarely found. We report of a GCT-ST of low malignant potential, which developed under long-term immunosuppression in a patient 12 years after heart transplantation. The tumor presented with an unusual aggressive course and metastatic site: the parotid gland. Therefore, we suggest that in patients with immunosuppression, even low malignant cancerous lesions should be carefully observed, as their local behavior may be aggressive with development of metastasis.