Nasal and nasal-type T/NK-cell lymphoma with cutaneous involvement.

Natural killer (NK) cells are a third lymphocyte lineage, in addition to B- and T-cells, that mediate cytotoxicity without prior sensitization. NK cells also have phenotypic and genotypic characteristics; they express the NK-related antigen CD56 and T-cell markers such as CD2 and CD3 epsilon, but their T-cell receptor (TCR) locus is not rearranged. Non-Hodgkin's lymphomas are divided into B- and T-cell neoplasms and NK-cell lymphomas. We describe 2 Japanese patients with nasal and nasal-type T/NK-cell lymphoma in which the skin, nasal/nasopharyngeal region, bone marrow, and lymph node were the sites of involvement. The clinical and histopathologic findings were recorded. In addition, immunophenotyping, TCR gene rearrangement, and the existence of Epstein-Barr virus (EBV) DNA by polymerase chain reaction amplification were determined. Clinically, the cutaneous eruptions were purplish, hard, multiple nodules. Histologically, angiocentric proliferation of small-to medium-sized, pleomorphic, lymphoid cells were observed. They revealed hand-mirror-shaped lymphocytes with azurophilic granules with the use of Giemsa staining by touch smear. These lymphocytes were found to be positive to immunophenotyping for CD2 (Leu5b), CD3 epsilon (DAKO), CD4 (Leu3a), and CD56 (Leu 19). No clonal rearrangement of TCR-beta, -gamma, and -delta genes and immunoglobulin gene markers were found, and no positive results of identification of EBV DNA were shown. The patients underwent cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy with complete remission; however, both had recurrence of disease. Because NK-cell lymphomas express some T-cell markers, they may be mistakenly diagnosed as peripheral T-cell lymphomas if they are not investigated for the NK-cell-specific marker, CD56. Therefore the importance of immunophenotypic investigations of CD56 should be stressed. Also, the importance of clinical investigation of nasal/nasopharyngeal lymphomas should be stressed when NK-cell lymphoma is diagnosed involving the skin, because NK-cell lymphomas are often associated with the nasal and nasopharyngeal region.