부산대학교 도서관

Natural killer (NK) cells are an element of innate immunity and distributed in lymphoid tissue, spleen, and extranodal sites. NK cell-associated lymphoproliferative disorder includes NK/T cell lymphoma; nasal type and aggressive NK cell leukemia (ANKL) exhibit poor outcomes. Here, we describe a case of young man who presented with fever, nausea, vomiting, diarrhea, and lymphadenopathy accompanied by crampy abdominal pain. Gastrointestinal work-up colonoscopy/endoscopy/HiDA scan was negative. Laboratory examination revealed atypical lymphocytes (WBC 9 × 109/L, hemoglobin 14.3 g/dL, and platelets 114 × 109/L). Serum Epstein-Barr virus (EBV) DNA level detected by PCR was elevated (7,000 copies/uL), and LDH ~447 IU. The bone marrow aspirate smears showed increased atypical lymphocytes cells intermediate in size, with round to irregular nuclear contours, basophilic cytoplasm, and some with cytoplasmic azurophilic granules. Flow reveals an atypical NK cell population (~28% of total), positive for CD8; expressing CD2, CD7, and CD56; and negative for CD4, TCR alpha/beta, TCR gamma/delta, and CD57. By immunohistochemistry, neoplastic cells were positive for CD2 (partial), CD8, CD7, CD56, and cytotoxic granules granzyme B and TIA-1; they were negative for CD3, CD30, CD5, CD10, CD4, CD57, CD25, and perforin. EBV by EBER in situ hybridization was strongly positive in the neoplastic cells. Extensive examination revealed absence of any skin lesions, predominantly systemic (blood and bone marrow) presentation and an interstitial leukemic pattern of infiltration in the marrow favored a diagnosis of ANKCL. Cytogenetic studies revealed normal karyotype without any abnormal clone. In conclusion, we describe a rare case characterized by atypical NK-cell proliferative lesions involving the bone marrow in young patient but without any cytogenetic studies and indolent clinical course. Morphologic and phenotypic overlap with non-neoplastic NK-cells and other mature NK-cell neoplasms, lack of specific cytogenetic abnormalities, and lack of a clonality marker in NK-cells make the diagnosis of ANKL challenging as described in this case. [ABSTRACT FROM AUTHOR]