[1624] Challenges in the Differential Diagnosis and Subtyping of Primary Central Nervous System Lymphomas.

Ellen F Krasik, Melike Pekmezci, Tarik Tihan. University of California San Francisco

Background: In surgical neuropathology, the challenges in the diagnosis of primary central nervous system lymphoma (PCNSL) include defining prognostic markers and the difficulties in being able to exclude a systemic lymphoma. Recent studies identified two general subtypes of diffuse large B-cell lymphoma (DLBCL) with different prognostic features based on MUM-1, BCL6 and CD10 expression. The utility of this subtyping in the CNS is not entirely clear.
Design: In order to determine the challenges in the diagnosis and prognostication of PCNLS, we reviewed the Department of Pathology archives over the last 20 years. Cases without sufficient information or pathological material were excluded. Clinicopathological and immunohistochemical features of were correlated with outcome parameters.
Results: Among 136 cases diagnosed as PCNSL during the last 20 years, we included 97 patients into the study. Sixteen patients (17%) were subsequently proven to have systemic lymphoma. Among the remaining 81 patients, 58 (32 male 26 female) had no evidence of immunosuppression. The median age of this group was 63 and all tumors were in the cerebral hemispheres except for 3 in the cerebellum and one in the midbrain. In 18 patients (15 males, 3 females), HIV/AIDS was established both clinically and serologically. In this group, the median age was 38 and only two tumors were outside the cerebral hemispheres. In addition, 5 patients fulfilled the criteria for monomorphic B-cell PTLD. The diagnosis could be established only after immunohistochemical stains in 38 of the 97 patients. The primary suspicion was demyelinating disease in 6 cases and a poorly differentiated malignancy (undifferentiated carcinoma, glioblastoma or melanoma) in 36 cases. Markers utilized in this study were not helpful to distinguish a systemic DLBCL from PCNSL.
Conclusions: Most pertinent diagnostic challenges in PCNSL include “treated” lymphoma versus demyelinating disease and other malignant small blue round cell tumors. Work-up of PCNSL should include exclusion of a systemic disease, especially in older individuals without HIV/AIDS. Our results also support the conclusion of recent reports on the phenotypic aspects of PCNLS and question the utility of the recent DLBCL subtyping in the CNS.
Category: Neuropathology

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 240, Tuesday Afternoon

 

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