Primary Ki-1 (anaplastic large cell) lymphoma of the brain and spinal cord.

The authors report a case of primary Ki-1 lymphoma of the brain. The patient was a 4 1/2-year-old black girl who presented with a 4- and 5-day history of headaches, nausea, vomiting, neck stiffness, and difficulty in walking. Computed tomography (CT) scan of the brain showed two discrete densities in the left occipital lobe and in the brain stem. Magnetic resonance imaging (MRI) showed multiple densities scattered over the brain surface and brain stem. Microscopically, the tumor was an anaplastic neoplasm that diffusely infiltrated brain parenchyma. The neoplastic cells were large with amphophilic cytoplasm, large nuclei with irregular nuclear contours and prominent nucleoli. A high mitotic rate including atypical mitotic figures was noted. Immunohistochemical stains showed diffuse strong positivity for CD30 and moderate focal staining for epithelial membrane antigen. Leukocyte common antigen, cytokeratin, neuron specific enolase, monocyte/macrophage and B- and T-marker stains were negative. The histology was characteristic for Ki-1 large cell lymphoma. Cytologic examination of cerebrospinal fluid (CSF) demonstrated similar neoplastic cells. This is one of the first reports of this variant in the pediatric population.