Key clinical point: Malignant tenosynovial giant cell tumors are highly aggressive sarcomas with significant potential for locally destructive growth, distant metastases, and death from disease. Based on their morphologic and immunohistochemical features and the presence of CSF1 rearrangements, malignant tenosynovial giant cell tumors appear to originate from synoviocytes.
Main finding: In 10 tumors, malignant-appearing large mononuclear cells were consistently positive for clusterin and negative for CD163, CD68, and CD11c. Desmin was positive in a small minority of these cells. Areas in malignant tenosynovial giant cell tumor resembling pleomorphic spindle cell sarcoma or osteo/chondrosarcoma showed loss of clusterin expression. RANKL immunohistochemistry was positive in the large mononuclear cells in eight cases. Two cases showed an unbalanced rearrangement of the CSF1 locus. Follow-up of 0.5-66 months (mean 20 months) was available for 9 patients; 3 patients died of their disease, 3 others had lung and lymph node metastases, and 3 patients were disease-free.
Study details: Ten well-characterized malignant tenosynovial giant cell tumors, 8 primary and 2 secondary, were examined using detailed immunohistochemical analysis. Molecular cytogenetic study for CSF1 rearrangement was performed in a subset of cases. The tumors occurred in 7 men and and 3 women (mean age: 52 years; range: 26–72 years); 1 case involved the ankle/foot, 3 affected the finger/toe, 1 was on the wrist, 3 affected the pelvic region, 1 was on the leg (n = 1), and 1 was on the thigh.
Disclosures: The authors declared that they have no conflicts of interest.
Source: Al-Ibraheemi A et al. Modern Pathology; 11 Sept. 2018. https://doi.org/10.1038/s41379-018-0129-0
Al-Ibraheemi A et al. Modern Pathology; 11 Sept. 2018. https://doi.org/10.1038/s41379-018-0129-0
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