Brain stereotactic biopsy flow cytometry for central nervous system lymphoma characterization: advantages and pitfalls

Abstract

BackgroundBrain stereotactic biopsy (SB) followed by conventional histopathology and immunohistochemistry (IHC) is the gold standard approach for primary central nervous system lymphoma (PCNSL) diagnosis. Flow cytometry (FCM) characterization of fine-needle aspiration cytology and core needle biopsies are increasingly utilized to diagnose lymphomas however, no biological data have been published on FCM characterization of fresh single cell suspension from PCNSL SB. The aim of this study was to establish the feasibility and utility of FCM for the diagnosis and characterization of brain lymphomas from a tissue samples obtained by a single SB disaggregation.MethodsTwenty-nine patients with a magnetic resonance suggestive for PCNSL entered the study. A median of 6 SB were performed for each patient. A cell suspension generated from manual tissue disaggregation of a single, unfixed, brain SB, was characterized by FCM. The FCM versus standard approach was prospectively compared.ResultsFCM and IHC showed an high degree of agreement (89 %) in brain lymphoma identification. By FCM, 16 out of 18 PCNSL were identified within 2 h from biopsy. All were of B cell type, with a heterogeneous CD20 mean fluorescence intensity (MFI), CD10 positive in 3 cases (19 %) with surface Ig light chain restriction documented in 11 cases (69 %). No false positive lymphomas cases were observed. Up to 38 % of the brain leukocyte population consisted of CD8 reactive T cells, in contrast with the CD4 positive lymphocytes of the peripheral blood samples (P < 0.001). By histopathology, 18 B-PCNSL, only one CD10 positive (5 %), 1 primitive neuroectodermal tumor (PNET) and 10 gliomas were diagnosed. A median of 6 days was required for IHC diagnosis.ConclusionComplementary to histopathology FCM can contribute to a better characterization of PCNSL, although necrosis and previous steroid treatment can represent a pitfall of this approach. A single brain SB is a valid source for accurate FCM characterization of both lymphoma and reactive lymphocyte population, routinely applicable for antigen intensity quantification and consistently documenting an active mechanism of reactive CD8 T-lymphocytes migration in brain lymphomas. Moreover, FCM confirmed to be more sensitive than IHC for the identification of selected markers.

Flow cytometry shows added value in diagnosing lymphoma in brain biopsies

“…Given the frequently rapid clinical deterioration in CNS lymphoma and the negative impact of a lower performance score on survival, according to the two largest validated prognostic models, early diagnosis is may improve prognosis . Similar findings were reported in a much smaller cohort of 18 stereotactic biopsies recently . Cordone et al found a significant agreement between flow cytometry and immunohistochemistry diagnosis ( P = 0.0034).…”

“…They described a sensitivity and specificity of flow cytometry by immunophenotyping of 89% and 100%, respectively. In the 2/18 PCNSL biopsies not identified by flow cytometry more central necrosis was present, compared to biopsies with concordant results and both patients used corticosteroids prior to the biopsy . We did not find more central necrosis in our discordant biopsies and corticosteroid use did not differ between concordant and discordant pairs.…”

Long-term in vivo microscopy of CAR T cell dynamics during eradication of CNS lymphoma in mice

“…Several clinical trials have illustrated their potent antitumor efficacy in systemic B cell malignancies, including peripheral diffuse large B cell lymphoma (DLBCL) (5, 6). Importantly, more than 90% of PCNSL are of the DLBCL subtype, expressing the surface antigen CD19 (7). Recently, a case report illustrated the complete remission of a secondary CNS lymphoma in a patient treated with anti-CD19 CAR T cells (8).…”

Intraoperative squash cytology provides a qualitative intraoperative diagnosis for cases in which frozen section yields a diagnosis of equivocal brain tumour

“…We also note that intraoperative squash cytology provides both qualitative diagnosis as well as the opportunity for the pathology staff to request raw material for later flow cytometric analysis . Also, when the presence of a glioma is established, the neurosurgeon may be asked to obtain raw material for molecular genetic analysis, i.e.…”