Demyelinating Pseudotumours Presenting as Space Occupying Lesions Mimicking Brain Tumours- A Histopathologic Assessment of Seven Cases

Demyelinating lesions which present as solitary contrast-enhancing masses pose a diagnostic challenge for both radiologists and surgical neuropathologists and can mimic a number of intracranial space occupying lesions either neoplastic/inflammatory. Herein, a series of seven cases with particular emphasis on histopathological and immunohistochemical characterisation of these lesions was presented. The seven cases of Tumefactive Demyelinating Lesions (TDLs) diagnosed on histopathology include three males and four females with age ranging from 10 to 58 years (median-25 years) chiefly presenting with focal neurological deficits. Radiologically, the lesions were predominantly localised in the temporo-parietal region. Histologically, the lesions were well-demarcated, hypercellular with infiltration by foamy macrophages and reactive astrocytes. In addition, Creutzfeldt astrocytes and granular mitoses were seen. Additional special stains for myelin (Luxol fast blue), demonstrated focal, sharply marginated loss of myelin, and Immunohistochemistry (IHC) with Neurofilament (NF) for axons showed relative preservation of axons in areas of myelin loss. IHC with Glial Fibrillary Acidic Protein (GFAP) highlighted the fibrillary processes of the reactive astrocytes and the cytoplasm of the Creutzfeldt cells. Knowledge of the characteristic features such as well-demarcated lesions with histological characterisation by large number of macrophages, including Creutzfeldt astrocytes, granular mitoses and perivascular inflammation should raise index of suspicion and prompt pathologist to do additional myelin stains and IHC to confirm demyelination and preservation of intact axons thereby, differentiating from neoplasms and other non-neoplastic inflammatory lesions.