Posttransplant lymphoproliferative disorders (PTLDs) represent a spectrum ranging from Epstein-Barr virus (EBV)-driven polyclonal lymphoid proliferations to EBV+ or EBV- malignant lymphomas. Central nervous system (CNS) PTLDs have not been characterized fully. We reviewed the clinical, radiologic, and pathologic features of 12 primary CNS PTLDs to define them more precisely. Patients included 10 males and 2 females (median age, 43.4 years) who were recipients of kidney (n = 5), liver (n = 2), heart (n = 2), peripheral blood stem cells (n = 2), or bone marrow (n = 1). All received immunosuppressive therapy. CNS symptoms developed 3 to 131 months (mean, 31 months) after transplantation. By neuroimaging, most showed multiple (3 to 9) intra-axial, contrast-enhancing lesions. Histologic sections showed marked expansion of perivascular spaces by large, cytologically malignant lymphoid cells that were CD45+, CD20+, EBV+ and showed light chain restriction or immunoglobulin gene rearrangement. In distinction to PTLDs in other organ systems, CNS PTLDs were uniformly high-grade lymphomas that fulfilled the World Health Organization criteria for monomorphic PTLDs. Extremely short survival periods were noted for each CNS PTLD that followed peripheral blood stem cell transplantation. Survival of others with CNS PTLD varied; some lived more than 2 years.

We evaluated HER-2 receptor status by immunocytochemical and immunohistochemical analyses and fluorescence in situ hybridization (FISH) in 51 fine-needle aspiration (FNA) specimens together with the corresponding formalin-fixed, paraffin-embedded (FFPE) tissue samples obtained from surgically resected breast cancers. Three fixation methods were compared: ethanol, formalin, and CytoLyt-ThinPrep (Cytyc, Boxborough, MA). HER-2 was overexpressed and amplified in 8 (16%) of 51 FFPE specimens. Of the 8 cases, gene amplification was observed in 8 FNA specimens (100%) and overexpression in 2 (25%) ethanol-, 4 (50%) CytoLyt-, and 5 (63%) formalin-fixed FNA specimens. Strong pairwise kappa association between FISH results performed on FNA specimens and FFPE tissue samples (ethanol fixation, kappa = 0.848; ThinPrep, kappa = 0.918) and moderate (ThinPrep, kappa = 0.692; formalin fixation, kappa = 0.667) to poor (ethanol, kappa = 0.300) pairwise kappa agreement between tissue immunohistochemical and FNA immunocytochemical results was demonstrated. We conclude that HER-2 protein expression on cytologic preparations was insufficiently reliable for clinical use, whereas HER-2 gene amplification determined by FISH demonstrated strong and consistent correlation with HER-2 status of FFPE tissue samples.

The Ki67 stain alone is a powerful tool for distinguishing benign from malignant proliferations within the selected groups. Nuances and pitfalls in the interpretation of Ki67 staining pattern are discussed.

Objective Antibodies to glutamic acid decarboxylase (GAD) have been described in a few patients with temporal lobe epilepsies consistent with limbic encephalitis (LE). We studied a cohort of patients with recent‐onset temporal lobe epilepsy caused by LE to test for GAD antibody positivity and response to immunotherapies. Methods Over a period of 3.75 years, 138 patients aged ≥18 years investigated at the Department of Epileptology, University of Bonn, for recent‐onset epilepsy were prospectively collected and studied for cliniconeuroradiological features of LE, autoantibodies, and treatment responses. Results Fifty‐three adult patients fulfilled the criteria for LE: (1) limbic signs and symptoms for ≤5 years and (2) brain MRI revealing mediotemporal encephalitis (T2/fluid attenuated inversion recovery hyperintensity without atrophy). Nine had high‐titer GAD antibodies; 10 had voltage‐gated potassium channel (VGKC) antibodies. Patients with GAD antibodies were younger (median age, 23 years; range, 17‐66 years) (p = 0.003) and presented with seizures only, whereas polymorphic limbic features were more common in the VGKC antibody‐positive group (p < 0.001). None had tumors. Patients with GAD antibodies more frequently had cerebrospinal fluid oligoclonal bands (p = 0.009) and intrathecal secretion of the specific antibody (p = 0.01). Following monthly intravenous methylprednisolone pulses, GAD antibodies remained highly elevated in 6/6 patients, whereas VGKC antibodies normalized in 6/9 patients (p = 0.03). Despite more intense anticonvulsive treatment in the GAD antibody‐positive group (p = 0.01), none of these patients became seizure free, unlike all of the patients with VGKC antibodies (p < 0.001). Interpretation High‐titer GAD antibodies define a form of nonparaneoplastic LE. This is a chronic, nonremitting disorder and should be included in the differential diagnosis of patients with TLE and mediotemporal encephalitis. Therapeutic trials of other immunotherapies should be undertaken. ANN NEUROL 2010;67:470–478