The patient underwent a burr hole biopsy of the left occipitoparietal lesion.
Histology:
MACROSCOPIC DESCRIPTION:
Multiple fragments of soft pale fawn tissue up to 4mm in maximum dimension taken from periventricular area lesion. Reactive changes demonstrated. No tumour.
MICROSCOPIC DESCRIPTION:
Paraffin sections show fragments of cerebral white matter. These show predominantly perivascular collections of mononuclear cells with reniform vesicular nuclei. The cytoplasm of these cells is distended by granular eosinophilic material which is strongly PAS +ve and also shows uptake of methenamine-silver. These cells show strong CD68 immunoreactivity and are admixed with small mature CD3+ T lymphocytes, CD20+/CD79a+ B lymphocytes and microglial cells. No S-100 reactivity is seen in the mononuclear cells. The perivascular collections of these cells are sharply demarcated from surrounding white matter. No atypical oligodendrocytes or "ground glass" cells are seen and there is no evidence of emperipolesis of either erythrocytes or lymphocytes. No evidence of tumour is seen and no organisms or viral inclusion bodies are identified. Paraffin sections had been sent for Tropheryma Whippelii PCR and Polyomavirus DNA PCR, the results of which were both negative.
DIAGNOSIS: "Periventricular lesion": Non-Langerhans cell histiocytic proliferation consistent with Erdheim-Chester Disease. No evidence of tumour seen.