Tenosynovial giant cell tumors as accidental findings after episodes of distortion of the ankle: two case reports

The two faces of giant cell tumor of bone

Giant cell tumor (GCT) is a bone-destructive benign neoplasm characterized by distinctive multinucleated osteoclast-like giant cells with osteolytic properties distributed among neoplastic stromal cells. GCT is locally aggressive with progressive invasion of adjacent tissues and occasionally displays malignant characteristics including lung metastasis. GCT is characterized genetically by highly recurrent somatic mutations at the G34 position of the H3F3A gene, encoding the histone variant H3.3, in stromal cells. This leads to deregulated gene expression and increased proliferation of mutation-bearing cells. However, when GCT complicates Paget disease of bone (GCT/PDB) it behaves differently, showing a more malignant phenotype with 5-year survival less than 50%. GCT/PDB is caused by a germline mutation in the ZNF687 gene, which encodes a transcription factor involved in the repression of genes surrounding DNA double-strand breaks to promote repair by homologous recombination. Identification of these driver mutations led to novel diagnostic tools for distinguishing between these two tumors and other osteoclast-rich neoplasms. Herein, we review the clinical, histological, and molecular features of GCT in different contexts focusing also on pharmacological treatments.

Tenosynovial giant cell tumor arising from the posterior cruciate ligament: a case report and literature review

The localized form of tenosynovial giant cell tumor or pigmented villonodular synovitis is rarely intraarticular in the knee. We reported a 40-year-old woman with a tenosynovial giant cell tumor arising from posterior cruciate ligament (PCL). She suffered sudden knee pain and locking without any reason for two days. A mass with a size of 1.7 × 0.8 × 0.7 cm in the fossa intercondyloidea was detected on the MRI. After one time hyperextension physical examination the patients felt sudden pain relief. During the arthroscopy examination, a loose soft tissue mass was found under the lateral meniscus. Only the synovium tissue lesion on the proximal PCL was detected. The mass had a conceivable thin pedicel and the shape matched well with the tumor bed on the PCL. The histopathology of the mass demonstrated a tenosynovial giant cell tumor. At six weeks follow-up, no clinical evidence of recurrence was noted. A Literature Review of tenosynovial giant cell tumor or pigmented villonodular synovitis arising from the PCL is present.