gms | German Medical Science

Objective: We present a patient with a polytopic CNS tumour raising the differential diagnosis of an unusual histiocytic tumour and an anaplastic glioma. Several biopsies of brain and spinal lesions with repeated histological and immunohistochemical analyses showed cell characteristics indicating mainly histiocytic, but also partly glial origin, and inflammatory changes.

Method: A 50 year-old-male patient presented with brachialgia, paresthesia of the legs and ataxia.

Results: MRI: space occupying lesion C6/7 which was removed and showed inflammation. Detailed CSF examination was inconclusive. Bone marrow biopsy, CT thorax and abdomen: normal. Subsequently, lumbar spinal lesions were detected. Neuropathology: chronic neuritis. Symptoms progressed in spite of steroids. Additional brain lesions were diagnosed by serial MRI brain and F18-FET-PET. Biopsies of a frontal lesion and, later, of a lesion in the right caudate nucleus revealed a malignant tumour with chromatin rich small cells, elongated nuclei lacking prominent cytoplasm; expression of CD45, CD68, CD11c, and CD163 epitope, but negative for S100 protein and Langerin leading to the diagnosis of an unusual histiocytic tumour. Treatment was initiated with Vinblastin and steroids (protocol for Langerhans cell histiocytosis) with no improvement. Imaging showed tumour progression. Methotrexate and Ifosfamide were also unsuccessful and treatment then changed to high-dose chemotherapy with stem cell rescue (Freiburg protocol for primary CNS lymphoma). After 2 cycles of HD-Cytarabin/Thiotepa, all MRI lesions disappeared and the patient reached complete remission. 8 weeks later the patient deteriorated as he had developed new lesions in the posterior fossa and compression of the 4^th ventricle. Histopathology of a removed cerebellar lesion revealed tumour cells with the same characteristics as before. Some areas, however, harbored tumour cells with fibrillary processes, expression of GFAP / S100 protein, suggesting astrocytic differentiation. As an immunoreactivity of glioma cells with antibodies against histiocytic epitopes has been reported, further molecular profiling was suggested (450k Array) which is expected to differentiate between tumours of histiocytic/haematopoietic and glial origin.

Conclusion: This highly unusual pleomorphic CNS tumour cannot be classified on the basis of morphology and immunophenotype with certainty. This case illustrates the necessity of molecular analyses in the neuropathologial diagnostic pipeline in order to initiate appropriate treatment.