White epidermoid: A diagnostic dilemma

A 27-year-old female patient presents with a chronic headache. Physical examination and laboratory tests show no remarkable abnormality. MRI brain with contrast was ordered for further evaluation of symptoms. MRI revealed a large extra-axial, posterior fossa base T1 hyperintense and T2 hypointense lesion. The Lesion showed FLAIR hypointensity with no significant diffusion restriction on DWI. Post contrast scans show no contrast enhancement. Based on the T1 hyperintensity, lesions with hyperintense contents were kept in differential diagnosis such as dermoid and proteinaceous cyst. However, the lesion demonstrated T2 and flair hypointensity suggesting a highly viscous contents within the lesion. The loss of diffusion restriction ruled out any possibility of classical epidermoid cyst. The patients was kept on follow up with suggestion to remove the lesion surgically, although patient denied for surgical management and kept on symptomatic treatments with painkillers and multivitamins. This case report highlights the diagnostic dilemma in forming an MRI based diagnosis with dictation of a phenomenon where a lesion can exhibit a opposite character rather than exhibiting a classical intensity based on its contents. We can encounter a completely different imaging appearance of a lesion than what we thought to and should be kept in mind. This case report also highlights the fact that although the histopathology is main study of diagnosis and treatment in many cases it cannot be achieved in every case and management could rely purely on imaging findings.