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Retroperitoneal undifferentiated pleomorphic sarcoma having microsatellite instability associated with Muir-Torre syndrome: case report and review of literature


Dr Alexander J. Lazar, MD, PhD

Department of Pathology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd Unit 085, Houston, TX 77030-4009, USA

Tel: +1 713 563 1843

Fax: +1 713 563 1848



Muir-Torre syndrome represents a rare autosomal dominant familial cancer predisposition disorder defined by the occurrence of cutaneous sebaceous tumors and an internal malignancy, most commonly gastrointestinal carcinoma. Most examples of hereditary non-polyposis cancer syndrome (Lynch syndrome), including the Muir-Torre syndrome, are associated with microsatellite instability (MSI) and germline mutations in mismatch repair genes—most commonly MLH1 or MSH2. We present a 58-year-old man with Muir-Torre syndrome and a large retroperitoneal mass (14.3 cm in greatest dimension) encompassing the left adrenal gland. Sections showed a cellular malignant tumor composed of spindle cells with a high mitotic index and lacking morphologic evidence of adipocytic differentiation. It was weakly reactive for smooth muscle actin (SMA) and negative for desmin, CD117, CD31, CD34, S100 protein and pan-cytokeratin. Further immunohistochemical analysis revealed intact expression of MLH1 but loss of MSH2 in tumor nuclei. Compared to non-neoplastic tissue, the tumor showed MSI in five of seven dinucleotide markers. Fluorescence in situ hybridization (FISH) failed to reveal 12q15 amplification, effectively excluding dedifferentiated liposarcoma as a diagnostic consideration. This is a rare case of a patient with Muir-Torre syndrome who developed a related high-grade undifferentiated pleomorphic sarcoma as the associated internal malignancy.