Central nervous system lymphomas: a histologic and immunophenotypic analysis

To observe the spectrum of non-Hodgkin's lymphomas involving the central nervous system including morphological subtypes and immunophenotypic status.

Retrospective analysis of eleven years (1986 to 1996) data from surgical pathology files of Department of Pathology.

Forty-three cases of non-Hodgkin's lymphomas were diagnosed during the period of eleven years (from 1986 to 1996), all of which were diffuse types. A total of 1177 Central Nervous CNS biopsies were examined, out of which 937 cases were diagnosed as CNS neoplasms, the remaining were non-neoplastic in nature. Among 937 CNS neoplasms, 43 cases (4.6%) were reported as non-Hodgkin's lymphomas. As most of the cases were outside referrals, the primary or secondary nature of the lymphomatous process could not be assessed. Seventeen cases were intracranial, while 26 cases were spinal in location. Majority of the intracranial lymphomas were biopsied from the cerebrum (12 cases). Male to female ratio was 1:2. The median age for intracranial lymphomas was 50 years and for spinal lymphomas 29 years. There were 16 cases (37%) of diffuse large cell lymphomas; 7 cases (16%) of diffuse mixed small and large cell lymphomas; 3 cases (7%) of diffuse large cell immunoblastic lymphomas; 2 cases (4.6%) of lymphoblastic lymphomas and diffuse small non-cleaved cell lymphomas and one case of small lymphocytic lymphoma and diffuse small cleaved cell lymphoma. One case of T cell rich B cell lymphoma was also diagnosed in the thoracic spine as primary extranodal lymphoma. Eight cases were unclassifiable and in 2 cases the features were suggestive of lymphoma. Immunophenotypic analysis was performed in 20 cases, however, in 2 cases the results were inconclusive. Fifteen cases (83%) showed immunoreactivity for B cell markers and 3 cases showed T cell phenotype out of which one case was lymphoblastic lymphoma.

CNS lymphomas were uncommon tumors and comprised 4.6% of the total CNS neoplasms in our study. Moreover, these CNS lymphomas accounted for 2.2% of the total non-Hodgkin's lymphomas, including both nodal and extranodal. There was a higher incidence of location of these lymphomas within the spinal cord than brain. Most of the lymphomas were of intermediate or high grade (75%) according to the working formulation. Immunophenotypical status revealed B-cell phenotype in 84% of the lymphomas, in which it was tested (JPMA 50:141, 2000).