gms | German Medical Science

Objective: Primary central nervous system lymphoma (PCNSL) is a rare neurological disease, with a constant increasing incidence in recent years, up to 6% of primary intracranial tumours in different neuropathological series. The incidence rises up to 25% when only multiple brain lesions have been considered. Neurosurgical removal of PCNSL has any relevant therapeutic role and does not increase the survival, being chemo and radiotherapy the mainstays of therapeutic strategy. Nevertheless, tumour bioptic sampling remains the gold standard for PCNSL diagnosis in all patients, and stereotactic biopsy (SB) is the method of choice, allowing biopsy of deep-sited lesions that could not be approached safely with conventional open surgery. However, SB could be inconclusive in a limited number of cases (10–15% of cases), mainly after high dose steroid treatment, and a second diagnostic biopsy is eventually required at the moment of clinico-radiological recurrence.

Methods: Flow cytometry immunophenotyping (IF) is an indispensable tool for the diagnosis and monitoring of haematological malignancies in routine clinical practice; however it has not been reported for the diagnosis of SB in PCNSL. In this study, in addition to conventional histopathology, we assessed the value of six-colour flow cytometry IF on biopsy specimens obtained with SB biopsy in 8 patients affected by presumed PCNSL brain tumours. After tissue dissociation a single cell suspension was obtained for flow cytometry analysis. Diagnostic characterization of the leukocyte population was performed, with a number of >15,000 valuable events, in all the samples.

Results: A proportion of CD45 CD19 CD20 CD22 positive, CD79b CD5 CD10 CD34 negative large cells was identified, allowing the diagnosis of large B cell lymphoma in three cases. A significant infiltration of T CD2 CD3 CD5 CD8 positive lymphocytes was observed, ranging from 10% to 40% of the CD45 leukocyte population. In the other cases a diagnosis of primary malignant brain tumour was suspected by flow cytometry. All the diagnosis were confirmed by histopathology.

Conclusions: Flow cytometry IF of stereotactic biopsy appears a new powerful, reliable and rapid technique (two hours) for the diagnosis of PCNSL; a more extensive utilization of this technique could realize a relevant improvement in diagnostic approaches as well as therapeutic strategies of brain tumours.