Stereotaxic biopsy diagnosis of central nervous system lymphoma.

Twelve cases of central nervous system lymphoma diagnosed by stereotaxic brain biopsy are reviewed to determine the most effective method to establish the diagnosis given the small amount of tissue obtained by this technique. The stereotaxic biopsy material was examined cytologically, histologically, and immunocytochemically. The diagnosis was established by a smear made at the time of biopsy in eight cases. Histologic sections were diagnostic of lymphoma in 11 of 12 cases. Accurate classification according to the Working Formulation was possible in six cases, with diagnosis of diffuse small non-cleaved non-Burkitt's in three, large cell immunoblastic in two, and mixed small and large cell type in one. Five additional cases were diagnosed as high-grade lymphoma but could not be further subclassified because of the small biopsy size or formalin fixation. Immunocytochemical stains for lymphoid markers on paraffin-embedded material confirmed the diagnosis in ten cases, and, in one of these, the demonstration of monoclonality on air-dried cytospins identified an atypical polymorphous lymphocytic population as neoplastic.