CNS T-cell lymphoma: an under-recognized entity?

Abstract

The incidence of CNS lymphoma has increased significantly in the past 30 years, primarily in the elderly and immunocompromised. While T-cell lymphomas comprise 15-20% of systemic lymphomas, they comprise less than 4% of primary CNS lymphomas, suggesting that they may be under-recognized compared to their systemic counterparts. To investigate this, we studied brain biopsies from three patients who were diagnosed with T-cell lymphoma confined to the brain. They had enhancing lesions by MRI, arising in the cerebellum and brainstem in one and temporal lobe in two. We compared these to biopsies from three patients who had reactive lymphoid infiltrates and who had clinical signs/symptoms and radiographic findings that were indistinguishable from the lymphoma group. Biopsies from both the lymphoma group and reactive group showed considerable cytomorphologic heterogeneity. Although one lymphoma case contained large atypical cells, the other two contained small, mature lymphocytes within a heterogeneous infiltrate of neoplastic and reactive inflammatory cells. Surface marker aberrancies were present in two lymphoma cases, but this alone could not reliably diagnose T-cell lymphoma. The proliferation index was not useful for differentiating lymphoma from reactive infiltrates. In five of the six cases the diagnosis was most influenced by clonality studies for T-cell receptor-gamma gene rearrangements. We conclude that because of the high degree of overlap in cytomorphologic and immunophenotypic features between T-cell lymphoma and reactive infiltrates, T-cell lymphoma may not be recognized unless studies for T-cell receptor gene rearrangements are performed for CNS lesions composed of a polymorphous but predominantly T-cell infiltrate.

Primary Central Nervous System T-Cell Lymphoma of the Brain

“…Cystic degeneration with necrosis and hemorrhage are consistent within both populations [3]. T-cell PCNSL has consistent histological features including small nuclei, bland morphology without high grade features, heterogeneity and angiocentricity [2,3,5,[10][11][12]. The histopathologic appearance of T-cell PCNSL can include loosely scattered cells without solid mass formation and frequent perivascular infiltration [2].…”

“…However, as in our patient who had multiple lesions despite being immunocompetent, it highlights the fact that PCNSL can present in many different forms. Cystic degeneration with necrosis and hemorrhage are consistent within both populations [3]. T-cell PCNSL has consistent histological features including small nuclei, bland morphology without high grade features, heterogeneity and angiocentricity [2,3,5,[10][11][12].…”

“…It remains a very rare entity despite a gradual increase in global incidence. The reason for the initial rise in incidence had been linked to a growing immunocompromised population, in part due to, acquired immune deficiency syndrome (AIDS), increased prevalence of human immunodeficiency virus (HIV) infection, organ transplantation and the elderly [2][3][4]. However, due to advances in antiretroviral therapy the incidence of PCNSL in the immunocompromised population has been decreasing, yet the incidence of PCNSL in the immunocompetent population has been rising without clear explanation.…”

“…The occurrence rate of B-cell lymphomas is much more common than T-cell lymphomas and this concept hold true both in systemic and CNS presentation of lymphomas [2,5,6]. Of the cases of PCNSL reported, 98% are B-cell and 2% are T-cell lymphomas [3,6]. The prevalence of T-cell PCNSL is much higher in eastern countries, such as Korea (16%) and Japan (8-14%) compared to that of western countries such as France (3.6%) and the United States.…”

Primary Central Nervous System Lymphoma in Miyazaki, Southwestern Japan, a Human T-Lymphotropic Virus Type-1 (HTLV-1)-Endemic Area: Clinicopathological Review of 31 Cases

“…9,10 Additionally, Dulai et al indicated that T-PCNSL may not be recognized unless examinations are performed to detect Tcell receptor gene rearrangements for CNS lesions composed of a polymorphous but predominant T-cell infiltrate, because of a high degree of overlap in morphologic and immunophenotypic features between T-PCNSL and reactive infiltrate. 15 Conversely, a lesion of reactive T-cell infiltrate in the CNS can be misdiagnosed as T-PCNSL unless detection of T-cell receptor gene rearrangements is performed. There have been only a few reports of adult T-cell leukemia/lymphoma (ATLL) in PCNSL, 2,16 and no T-PCNSL including ATLL was detected in the present study, which was performed in an HTLV-1-endemic area.…”