Monomorphic epitheliotropic intestinal T-cell lymphoma involving the central nervous system: a rare case report with comprehensive autopsy neuropathological examinations.

Monomorphic epitheliotropic T-cell lymphoma (MEITL) of gastrointestinal tract is an aggressive T-cell lymphoma that can rarely involve the brain. We present detailed descriptions of clinical and autopsy neuropathological findings of a rare case of an elderly woman who had surgery and chemotherapy for MEITL of the small intestine. Following her surgery, she progressively exhibited neurologic decline towards the end of her treatment. The patient eventually succumbed to her illness and was found to have MEITL with intracranial involvement on autopsy. Brain autopsy was performed and examination of tissues with hematoxylin-eosin staining under optical microscopy with 100 X magnification. Immunostaining for CD3, CD4, CD5, CD7, CD8, CD56, CD20, beta-amyloid, c-Myc, TCR-beta, TCR-delta, and EBER-ish was conducted on the formalin-fixed paraffin-embedded (FFPE) brain tissues. A neuropathological exam revealed multifocal friable necrotic and hemorrhagic areas in the supratentorial region. Histologically, monotonous small to medium-sized atypical lymphocytes infiltrated the brain parenchyma, prominently around the vessels. The immunophenotype of the atypical lymphocytes was positive for CD-3, CD-7, and CD-56 and negative for CD-5, CD-4, CD-8, CD-20, and c-Myc. EBER-ish was negative. The histology and immunophenotype confirmed the MEITL brain involvement. Neurologic decline and cognitive changes in patients with known MEITL can be the first clue of brain involvement upon which prompt evaluation is warranted.