Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue arising in the lateral ventricle.

Extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) lymphomas are a well-described type of low-grade B-cell non-Hodgkin lymphoma. They typically arise adjacent to mucosal surfaces in the gastrointestinal tract, lung and conjunctiva, and, less frequently, in the skin, salivary gland and thyroid gland. Unusual locations, such as the genitourinary tract, thymus and meninges, have also been reported. We recently encountered a case of an intracranial MALT lymphoma in a 53-year-old man who presented with persistent headaches and a seizure. The lesion developed as a mass within the lateral ventricle, appeared to be arising from the choroid plexus, and was not associated with meninges. Histologically, there was a vaguely nodular, dense lymphoid infiltrate with occasional benign follicles colonized by marginal zone lymphoma, suggesting derivation from a focus of prior inflammation. Translocations involving the MALT1 gene were not identified but karyotypic evaluation highlighted a complex cytogenetic profile with many chromosomal abnormalities. This rare case provides insight into the pathophysiology of MALT lymphomas.