Background: A 37-year-old woman presented with a supratentorial cerebral mass, which was diagnosed histologically as a primitive neuroectodermal tumor. She had been treated for rectal adenocarcinoma 7 years previously. A family history revealed a young-onset colorectal carcinoma in the patient's father.
Investigations: Immunohistochemical analysis for DNA mismatch repair proteins, germline mutation analysis of MSH2.
Diagnosis: Lynch syndrome with a heterozygous germline mutation in MSH2.
Management: Debulking of the cerebral tumor, craniospinal axis radiotherapy, and genetic counseling of family.