Marked Increase of Circulating Double-Negative γδ T Cells in a Patient With Hydroa Vacciniforme-Like Lymphoma.

Dear Editor, Hydroa vacciniforme-like lymphoma (HVLL) is a disorder of childhood that is associated with Epstein–Barr virus (EBV). The characteristic clinical sign of HVLL is papulovesicular eruption and subsequent ulceration/scarring primarily on the face and upper extremities [1]. The neoplastic cells of HVLL are usually T cells and natural killer (NK) cells. Recently, increase of circulating EBV-infected γδ T cells has been demonstrated in patients with HVLL [2-4]. We report an unusual case of marked doublenegative (CD4-negative/CD8-negative) γδ T cell lymphocytosis, wherein the morphological findings resembled those of larger granular lymphocytic leukemia (LGL). A 4-yr-old girl presented with multiple facial erythematous papules and crust/patches. She had a history of persistent lymphocytosis (for seven months). At the time of visit to our hospital, her white blood cell (WBC) count, hemoglobin, and platelet levels were 29.44×10/L (lymphocytes: 76.6%, 22.55×10/L), 12.2 g/dL, and 364×10/L, respectively. Serologic results for EBV infection were as follows: EBV-viral capsid antigen (EBVCA) IgG, positive; EB-VCA IgM, negative; EBV-early antigen (EBV-EA), negative; EBV-nuclear antigen (EBNA) IgG, positive. The quantitative PCR result for EBV DNA was 186,620 copies/ mL. Large granular lymphocytes and small lymphocytes without significant atypia increased in the peripheral blood (PB) (Fig. 1A). Immunophenotyping revealed increase of double-negative γδ T cells in the PB (83% of lymphocytes); surface CD3-positive/CD4-negative/CD8-negative/CD16-negative/CD56-negative/ CD57-negative/T cell receptor (TCR)-γδ-positive (Fig. 1B). The flow cytometer, FACSCantoII, and monoclonal antibodies were purchased from Becton Dickinson (San Jose, CA, USA). Immunohistochemical staining results for the facial skin biopsies were as follows: CD3-positive, TCR-βF1-negative, TCR-CγM1-positive, CD4-negative, CD8-negative, CD20-negative, EBV in situ hybridization-positive, and Ki-67-positive (30%). To exclude T cell LGL (T-LGL), we analyzed STAT3 using PCR and sequencing after obtaining informed consent [5]. Primers for STAT3 were as follows: exon 19, Forward 5 ́-TTGGAACGAAGGGTAGGTTG-3 ́ and Reverse 5 ́-TTTGCGAGTCTGAGTGAAACA-3 ́; exon 20, Forward 5 ́-CCCCTTCGAGGAAAGAAAAA-3 ́ and Reverse 5 ́-CCAGGTTATTCAGGCATTTG-3 ́; exons 21-22, Forward 5 ́-GCAGATGGAGCTTTCCAGAC-3 ́, Reverse 5 ́-TCCTACCATTCCGAGTGACC-3 ́. Sequencing was performed by using the BigDye Terminator Cycle Sequencing Ready Reaction Kit on the ABI Prism 3130 Genetic Analyzer (Applied Biosystems, Foster City, CA, USA). No mutations were found in STAT3. HVLL was diagnosed according to the 2008 WHO Classification [6].