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Volume 8 (2004), Issue 4, Pages 123-127

Immunohistochemical Loss of the DNA Mismatch Repair Proteins MSH2 and MSH6 in Malignant Fibrous Histiocytomas

1Department of Oncology, the Jubileum Institution, University Hospital, Lund SE-221 85, Sweden
2Department of Pathology, University Hospital, Lund, Sweden
3Department of Clinical Genetics, Karolinska Hospital, Stockholm, Sweden

Copyright © 2004 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Purpose: Soft tissue sarcomas (STS) account for less than 1% of all malignancies and constitute a heterogeneous tumor entity in which malignant fibrous histiocytomas (MFH) represent one-third and are characterized by a lack of type-specific differentiation. A defective mismatch repair (MMR) system cause the familial cancer syndrome hereditary non-polyposis colorectal cancer (HNPCC), and since occasional MFH have been described in HNPCC patients we assessed the contribution of defective MMR to the development of MFH.

Methods: MMR status was characterized in a series of 209 histopathologically reviewed MFH. Tissue microarray sections from the tumors were immunohistochemically stained for the MMR proteins MLH1, MSH2 and MSH6, and cases with aberrant staining were further characterized for microsatellite instability.

Results and Discussion: Two of the 209 STS–a storiform-pleomorphic MFH and a myxofibrosarcoma–showed concomitant loss of MSH2 and MSH6, but retained staining for MLH1 on both cases. The myxoid tumor also had a microsatellite unstable phenotype. These findings, together with previous observations of defective MMR in pleomorphic STS, indicate that these tumors may be part of the HNPCC-associated tumor spectrum and demonstrate that MMR defects occur in a small subset of STS.