Muir–Torre syndrome-associated pleomorphic liposarcoma arising in a previous radiation field

Muir–Torre syndrome is a variant of Lynch syndrome, characterised by sebaceous neoplasia and/or keratoacanthomas associated with visceral malignancies. Muir–Torre syndrome is caused by germline mutations of one of the mismatch repair genes, frequently MSH2 and less frequently MLH1 and MSH6. Visceral malignancies associated with Muir–Torre syndrome and Lynch syndrome include colorectal, endometrial and other gastrointestinal, urological and gynaecological malignancies. Small numbers of Lynch syndrome-associated soft tissue sarcomas have been reported, but there are no reported cases of soft tissue sarcomas in Muir–Torre syndrome. In this study, we report a 74-year-old man with known Muir–Torre syndrome with confirmed MSH2 germline mutation, diagnosed with pleomorphic liposarcoma of the right buttock in a previous radiation field. The tumour showed loss of expression of MSH2 and MSH6 on immunohistochemistry. Immunohistochemistry on another pleomorphic liposarcoma in a different patient with no previous history of Muir–Torre syndrome or Lynch syndrome showed no loss of expression of mismatch repair proteins. This is the first report of Muir–Torre syndrome-associated sarcoma and the first case of post-radiation sarcoma in Lynch syndrome.