Diffuse large B cell lymphoma (DLBCL) arising within a ganglioglioma of the cerebellum.
We present a case of a primary central nervous system (CNS) DLBCL associated with a cerebellar ganglioglioma in an immunocompetent patient.
Gangliogliomas represent 0.4% of CNS tumor, and 1.3% of all brain tumors (6). The majority are supratentorial and involve the temporal lobe, where they are often associated with intractable epilepsy. Cerebellar gangliogliomas are rare. Primary CNS lymphomas are variably reported as representing from 0.8% to 6.6% of primary intracranial neoplasms (7), and just 13% of these arise in the posterior fossa.
Composite or 'collision' tumors in the CNS are infrequent enough that the only publications are as case reports. There have been previously published reports of collision pleomorphic xanthoastrocytomas (PXA) and gangliogliomas (1,4,8), some of which involved the cerebellum (1,4,8). However, in these cases the PXA represented the glial component of the ganglioglioma rather than being a completely independent tumor type. Another single case report of a composite ganglioglioma and dysembryoplastic neuroepithelial tumor arising in the temporal lobe has also been reported (9). However, there have been, to the best of the authors' knowledge, no previous reports of a primary intracranial DLBCL arising in a ganglioglioma, or in any other tumor within the CNS.
In contrast, there are a number of reports of lymphoma as part of an extracranial collision tumor. These tumors arise most frequently in the gastrointestinal tract, most commonly as mucosa-associated lymphoid tissue (MALT) lymphomas in collision with gastric adenocarcinoma (2,5), however, rare cases have been described elsewhere, such as the breast (10), and the lung (3). This is interesting as both MALT lymphoma and gastric adenocarcinoma are associated with H.Pylori infection. It is believed that the chronic gastritis associated with the infection results in activation and eventual malignant transformation of mucosal lymphoid tissue. This is believed to be a result of hyperstimulation of B lymphocytes by the reactive T lymphocyte population. Could it be similarly hypothesized that the normally polyclonal lymphoid infiltrate often seen in association with gangliogliomas, and as seen in this case, has undergone malignant transformation, resulting in a monoclonal population of neoplastic B lymphocytes? In this case the chronic antigenic stimulation would be the neoplastic cells of the ganglioglioma itself.
In summary we present what we believe to be a unique case of a posterior fossa collision tumor, comprising a primary intracranial DLBCL and a ganglioglioma of the cerebellum.
Contributed by Lisa Browning, John Leach, Christopher Watts, Wilhelm Kuker, Richard Stacey.