Numerous spindle-shaped lymphoma cells in lymphomatosis cerebri: An autopsy case report

Lymphomatosis cerebri (LC) is a rare variant of primary central nervous system lymphoma (PCNSL). It is characterized by diffuse infiltration of atypical lymphoid cells with no mass formation and little or no contrast enhancement on magnetic resonance imaging (MRI). Interestingly, some lymphoma cells form characteristic spindle shapes; these cells are found in some variants of malignant lymphoma, such as primary cutaneous follicle center lymphoma, but they have not been reported in PCNSL or LC. Here, we provide an autopsy case report of LC in a 69-year-old immunocompetent man who developed rapidly progressive cognitive decline and died on day 68 after the episode despite treatment with intravenous methylprednisolone administration. MRI revealed high signal intensities on T2-weighted images of the cerebral hemispheres, cerebellum, brainstem, and spinal cord without gadolinium enhancement on T1-weighted images. On autopsy, diffuse infiltrative atypical cells were seen; these cells were positive for CD20 and CD79a and negative for GFAP, CD3, and CD5 on immunohistochemistry, resulting in a diagnosis of diffuse large B-cell lymphoma, specifically LC. We found characteristic spindle-shaped cells, especially in the cerebral cortex. This is the first report showing that lymphoma cells in PCNSL can take on a spindle-shaped form. It is difficult to recognize these spindle-shaped cells as lymphoma cells on hematoxylin and eosin staining and diagnose them correctly with small biopsy specimens without immunohistochemistry. This case suggests that we should add atypical, spindle-shaped cells to the differential diagnosis of PCNSL.