LAUSR

A 71-year-old male presented with a 2-year history of aggressive behaviour, stumbling, shakes and falls. Initially treated for presumptive Parkinson’s disease, subsequent computed tomography demonstrated large frontal subdural haematomas and urgent surgical evacuation was undertaken. Unexpectedly, the histology showed fibrin-associated diffuse large B-cell lymphoma (DLBCL). Within the blood clot, there was a large population of atypical lymphoid cells with abundant cytoplasm and large nuclei with prominent nucleoli (left, haematoxylin and eosin, 960 objective). Immunohistochemistry showed the cells to express CD45, CD20 (right, 940), MUM1, BCL2, PAX5 and Epstein–Barr virus (EBV)-encoded RNA. The proliferative index was >90%. A bone marrow aspirate and trephine biopsy did not demonstrate a significant abnormality, showing only a mild increase in haemosiderin. This is an unusual subtype within the ‘DLBCL associated with chronic inflammation’ category. It does not usually lead to symptoms and is discovered incidentally on histological examination of surgical specimens excised for other reasons. It has been reported as an incidental finding associated with pseudocysts, atrial myxomas, prosthetic cardiac valves, chronic subdural haematomas and haematomas or thrombi associated with sites of prior vascular surgery. An intracranial location is very rare; previously reported cases were associated with subdural haematoma (four cases), an arachnoid cyst (one case) and a cerebral artery aneurysm (one case). The condition shows a male preponderance with a wide age range and frequently occurs in immunocompetent individuals. The pathogenesis is not known. The presence of foreign material and associated chronic inflammation may be contributing factors. Certain features appear to be common including location within a restricted anatomical space, single and small aggregates of large lymphoma cells with large B-cell morphology and immunophenotype present in a background of abundant fibrin and an association with EBV. Clinical behaviour is usually indolent and diagnosis can be challenging as fibrin-associated DLBCL is not usually mass forming. The prognosis appears to be favourable.