Squash cytology of primary central nervous system lymphoma in an immunocompetent patient.

The diagnosis of primary central nervous system lymphoma (PCNSL) can be suggested by magnetic resonance imaging (MRI). Cerebral PCNSL in immunocompetent patients generally shows marked homogeneous contrast enhancement in MRI. However, confirmation of it requires demonstration of lymphoma cells in stereotactic biopsy of the lesion or in cerebrospinal fluid. In the present case, with radiologic diagnosis of glioma, complete resection of the lesion by micro-neurosurgical technique was performed. The tumor tissue was examined by squash smear, frozen section and paraffin sections. Cytologic appreciation of tumor cells as lymphoid origin in squash smears negated the other possibilities. The immunocytochemistry on squash smear and immunohistochemistry on paraffin sections confirmed the diagnosis of diffuse large B cell lymphoma of non-germinal center B cell phenotype.