Rare Presentation of Relapsed Extranasal Natural Killer/T Cell Leukemia Lymphoma Involving the Hypothalamus

42 year old male was diagnosed with stage IV extranasal natural killer T cell leukemia/lymphoma in the liver in 2013. He was treated with 5 cycles of SMILE regimen and one cycle of gemcitabine based chemotherapy after which he achieved complete remission. He had 10/10 matched unrelated donor myeloablative allogeneic transplant on 2/26/2014. His Day 100 and 1 year work up showed complete remission and 100% donor chimerism. He had no chronic graft-versus-host-disease (cGVHD). In March 2015 he presented with change in mental status and electrolyte abnormalities. Patient was oriented to self only without focal neurologic deficits and initially presented with hypovolemic hypernatremia. His work up showed Central Diabetes Insipidous. CT head was unremarkable. MRI of brain showed bilateral hypothalamic, cerebellar and frontal hyperdensity concerning for tumor infiltration. Brain Biopsy of frontal lesion showed tumor cells diffusely infiltrating the neutrophil with perivascular predilection, tumor cells were positive for CD 3, CD 7, CD 56, bcl-2, and cytoplasmic positivity for granzyme B consistent with NK T cell leukemia/lymphoma. Cells were negative for EBV, CMV HSV, HHV-8, Polyoma virus and CD 20. This was similar to his pathologic finding at initial diagnosis. Further work up including bone marrow biopsy and aspirate, CSF analysis, and peripheral blood flow cytometry were unremarkable. He was treated with 6 cycles of high dose methotrexate. MRI brain at the end of treatment showed improvement in his brain lesion.

Mature T or NK/T-cell lymphoma makes up only 5-18% of all cases of non-Hodgkin lymphoma. In a case study among 1153 adult cases of peripheral T cell lymphoma, 11.8% were classified as extranodal NK/T cell lymphoma and only 26% of these were extranasal type. In published studies, NK/T-cell lymphoma extranasal type typically involve the skin, testis, cervix, intestine, liver, spleen, soft tissue, and orbit but CNS involvement is rare and has only been reported in only a select number of clinical cases. Primary CNS involvement of extranasal NK T cell lymphoma and direct intracranial extension and progression of nasal NK/T cell lymphoma have been reported as rare presentations however, to our knowledge, recurrence or relapse of extranasal NK/T cell lymphoma within the brain parenchyma and more importantly involving the hypothalamus after a year of disease remission has not yet been reported.