Brain Pathology Case of the Month - December 2005

Contributed by L. Fischer MD1, A. Korfel MD1, G. Stoltenburg-Didinger MD2, C. Ransco MD3, E. Thiel MD1
    1Department of Hematology, Oncology and Transfusion Medicine, Klinikum Benjamin Franklin, Freie Universitšt, Berlin, Germany
    2Department of Neuropathology, Klinikum Benjamin Franklin, Freie Universitšt, Berlin, Germany
    3Department of Pathology, Zentralklinik Emil von Behring, Berlin, Germany
Published on line in December 2005


CLINICAL HISTORY AND IMAGING:

A 19-year-old previously healthy man was admitted in an unconscious state with a conjugate deviation of gaze to the right. Having been intubated and ventilated, he suffered a series of generalized seizures. Cranial MRI showed a slightly enhanced periventricular edema zone in the white matter adjacent to the posterior horn (Fig. 1; A: fluid-attenuated inversion recovery [FLAIR], B: T2-weighed, C: gadolinium enhanced).

After discontinuing sedation, the patient had no focal neurological deficits on dexamethasone alone. A stereotactic biopsy revealed perivascular lymphoplasmacellular infiltration of mainly small lymphocytes with a prevalence of the B type. A few scattered B blasts were seen as well as numerous plasma cells monotypically expressing the immunoglobulin (Ig) lambda but rarely the kappa light chain. The growth fraction measured by Ki67 expression did not exceed 5%. Arterial walls were thickened and hyalinized. There were no signs of vasculitis or encephalitis. The four different pathologists who examined the material supposed a low-grade B cell lymphoma with plasmacellular differentiation.

The CSF examination showed 3.3 cells/ l and an elevated protein of 0.62 g/l. Oligoclonal bands were not observed in the CSF protein electrophoresis, and only polyclonal Ig heavy chain rearrangements were ascertained by CDIII-region PCR. No systemic lymphoma manifestations were found in the clinical examination or on chest and abdominal CT scans. A bone marrow (BM) biopsy did not show a lymphoma infiltration or an increase in plasma cells (5%). Immunoprecipitation showed no monoclonal gammopathy in blood or urine. Kidney and liver function parameters, echocardiography and ECG were normal. A mucosal biopsy taken from the lip revealed no pathological findings.

After 3 cycles of systemic methotrexate chemotherapy he suffered another generalized seizure. Carbamazepine was started, and no further seizures occurred. Since MRI showed no change in lesion size, another stereotactic biopsy was performed. Chemotherapy was stopped and MRI controls after 3 and 6 months demonstrated a slight decrease in lesion size. The patient's condition is still stable 24 months after the onset of the first symptoms.

MICROSCOPIC DESCRIPTION:

Histological examination revealed lymphocellular infiltration (Fig. 2A) containing an equal number of B and T cells as well as a few plasma cells (L26, Fig. 2B). The expression of the Ig lambda light chain (Fig. 2C) was predominant compared to kappa light chain (Fig. 2D) . The proliferation rate by MIB-1was 1-3% (Fig. 2E). We observed abundant amorphous eosinophilic material (Fig. 2A) without double refraction or congophilic properties. Therefore it was not amyloid. However, the material stained positive for the lambda light chain (Fig. 2F) whereas it was negative for kappa.

FINAL DIAGNOSIS



International Society of Neuropathology