Diffuse leptomeningeal glioneuronal tumor (DLGNT) mimicking Whipple's disease: a case report and literature review.

INTRODUCTION: Diffuse leptomeningeal glioneuronal tumor is a new entity under the neuronal and mixed neuronal-glial tumors in the WHO 2016 updated classification and commonly found in children and adolescents. The initial diagnosis is challenging because of its non-specific radiologic feature and negative CSF cytology analysis. A 17 years male was presented with intractable headache subsequently followed by back pain and joint pain. MRI showed enhancement of arachnoid membrane at basal cistern, bilateral sylvian fissure and cerebral cistern with slight enlargement of ventricles. There were no evidences of infection in CSF and blood samples. Based on the duodenal biopsy and prodromal symptom of joint pain, the patient was suspected of having Whipple's disease. Eleven months after the onset, a small mass lesion was observed at the anterior horn of right lateral ventricle. The histology was remarkable for anaplastic oligodendroglioma. Immunostainings revealed positivity for GFAP, Olig2, synaptophysin and negativity for IDH1 mutation, H3K27M. MIB1 labeling index was 40% and 1p19q FISH analysis showed only 1p deletion. Therefore, a final diagnosis of DLGNT was made.

CONCLUSION: DLGNT should be included as a differential diagnosis of patients with leptomeningeal-enhanced and high CSF protein level with normal white blood cell count.