Differential diagnosis of brain lesions in a metastatic endometrial carcinosarcoma patient.

The differential diagnosis of ring-enhancing brain lesions in a patient with metastatic malignancy may initially seem straightforward, and easily attributed to brain metastases. On rare occasions, the physician needs to avoid anchoring bias by re-evaluating the entire clinical context in which these ring-enhancing brain lesions are found. We report a case of cerebral toxoplasmosis mimicking brain metastases in a patient with metastatic cancer and without a prior history of human immunodeficiency virus. A 65-year-old lady with a recently detected relapse of her endometrial carcinosarcoma presented with a 2-week history of fever with no localising symptoms or signs of infection. The initial investigations were unremarkable. She had daily fever despite empirical broad-spectrum antibiotics. A positron emission tomography-computed tomography (PET-CT) was performed to evaluate the pyrexia of unknown origin, which showed metastatic deposits in the pelvis. A magnetic resonance imaging (MRI) of the brain was subsequently performed due to fluctuating mentation, which reported metastatic disease to the brain. Her pyrexia of unknown origin was attributed to malignancy-related fever. The medical oncologist was cautious about starting systemic treatment because the PET-CT had FDG-avid diffuse ground glass opacities in both lung fields, and requested for a bronchoscopic evaluation, which returned positive for