Inflammatory brain lesions preceding primary central nervous system lymphoma: a case report and genetic analysis

Primary central nervous system lymphoma (PCNSL) is an aggressive extranodal lymphoma exclusively occurring within the central nervous system. Inflammatory brain lesions as "sentinel lesions" of PCNSL are very rare. We present a rare case of PCNSL with preceding inflammatory lesions in an immunocompetent patient who underwent two biopsies, one craniotomy and two genetic testing.

A 66-year-old male patient presented with left limb weakness and ataxia. Brain magnetic resonance imaging showed a contrast-enhancing lesion with perifocal brain edema in the near midline of right frontal lobe. Histological examination of a brain biopsy specimen revealed inflammatory lesion characteristics with infiltration of T-cell dominant lymphocytes and few B-cell. Given that the patient developed cerebral hematoma after biopsy, lesion resection by craniotomy was performed. An excised sample demonstrated mixed T-cell and B-cell infiltrating inflammatory lesions. Four months after total resection of the right frontal lobe lesion, another lesion appeared in the left frontal parietal lobe, which was diagnosed as diffuse large B-cell lymphoma by biopsy. In addition, genetic testing of the lesions at two different locations was performed, and the results showed that the inflammatory lesions had the same three gene (RELN, PCLO, and CREBBP) mutations as PCNSL. Interestingly, the three mutated genes are associated with tumor.

Our present case is the first to demonstrate inflammatory brain lesions heralding PCNSL from genetic and pathological perspectives. This may help clinicians to select new auxiliary diagnostic methods for timely diagnosis of patients with suspected PCNSL.