Hydroxymethylcytosine (hmC) is a natural nucleobase, which is converted from methylcytosine (mC) by tet methylcytosine dioxygenase (TET) family (TET1-3) enzymes. Decrease of genomic hmC is postulated to confer a risk for myeloid-lineage as well as T-cell neoplasms, based on the fact that loss-of-function mutations in the TET2 gene were frequently identified in these diseases. The relationship between hmC and aging remains to be elucidated. Here, we demonstrated that hmC content decreased with age in the peripheral blood T cells of 53 human volunteers. We further identified that the mRNA expression levels of TET1 and TET3 decreased with age, while those of TET2 were not influenced by age. The genomic hmC content was correlated with the mRNA expression level of TET3, but not those of TET1 and TET2. Our study suggests the presence of new epigenetic regulatory mechanisms in aging T cells.

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We analyzed the histopathological characteristics of lymphomas biopsied from the upper aerodigestive tract between 2000 and 2014 at the National Cancer Center Hospital in Japan. Of a total of 309 consecutive cases, the following incidences were observed: mature B-cell neoplasms, 77% (n = 239); mature T- and NK-cell neoplasms, 20% (n = 63); classical Hodgkin lymphomas, 0.7% (n = 2); and lymphoblastic lymphomas, 2% (n = 5). Lymphomas were most frequently (57%) detected in the oropharynx. The majority of cases (89%) were mature B-cell neoplasms (diffuse large B-cell lymphoma, 60%; follicular lymphoma, 10%), and 10% of cases were mature T-cell neoplasms. Six cases of plasma cell neoplasm (4 primary and 2 secondary involvement) and 2 cases of plasmablastic lymphoma in the upper aerodigestive tract were observed. Two out of 3 cases of extraosseous plasmacytoma with available biopsy material were positive for EBER1. All 3 patients received irradiation and achieved complete response; 1 had not relapsed after 17 months and the remaining 2 relapsed as plasma cell myeloma and solitary plasmacytoma of the bone. Of 47 extranodal NK/T-cell lymphoma, nasal-type cases in the upper aerodigestive tract, 38 (81%) were present in the sinonasal region and the remaining 9 (19%) were in the oropharynx (n = 4), nasopharynx (n = 3), and oral cavity (n = 2). In conclusion, since both primary lymphoma and secondary involvement of lymphoma are often diagnosed using biopsied materials from the upper aerodigestive tract, pathologists and hematologists should recognize the characteristics of lymphoma in this tissue.

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Adult T-cell leukemia/lymphoma (ATLL) is a T-cell neoplasm caused by human T-cell leukemia virus type I (HTLV-I). ATLL is classified into four clinical subtypes based on the clinical manifestation: acute, lymphoma, chronic and smoldering. Approximately half of chronic type ATLL cases progressed to the acute type. We previously demonstrated that genomic alterations related to the cell cycle de-regulation such as CDKN2A and immune escape such as CD58 alteration can serve as predictive biomarkers for acute transformation of the chronic type. Although alteration of TP53, which is known to be a major regulator of cell cycle, has been identified in several types of cancers including acute type ATLL, no copy number alteration of TP53 was found in the chronic type by array comparative genomic hybridization. In the present study, mutation of TP53 was further analyzed by sequencing for these cases as well as HTLV-I carriers with oligo-clonality. However, no TP53 mutation was identified. These results suggested that TP53 mutation plays a role for the later stage of ATLL development.

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T-cell prolymphocytic leukemia, small cell variant (T-PLL-s), is a rare lymphoid neoplasm associated with a poor prognosis. We encountered a case of T-PLL-s with a characteristic phenotype. A 67-year-old female was referred to our hospital because of lymphocytosis in August 2013. Hepatosplenomegaly, lymphadenopathy, and skin lesions were absent. Hematologic examination revealed a white blood cell count of 17.9 × 10⁹/L with 81.2% mature lymphocytes, which were small with a high nuclear/cytoplasmic ratio, lacking a nucleolus and cytoplasmic granules. Anemia and thrombocytopenia were not observed. Flow cytometric analysis showed that these lymphocytes were positive for CD2, cyCD3, CD4, CD5, CD7, CD21, and CD38 (partially), but negative for smCD3, smTCR-αβ and -γδ, cyTCR-β, CD1a, CD8, CD25, HLA-DR, and terminal deoxynucleotidyl transferase. Polymerase-chain reaction analysis of cells from both the peripheral blood and the bone marrow demonstrated monoclonal rearrangement of TCR-γ. A possible rearranged band of the TCR-β gene was observed by Southern blot analysis. The karyotype of the marrow cells was 46, XX. A diagnosis of T-PLL-s, possibly at the stage of cytoplasmic CD3 expression in the ontogenesis of T-cells, was made. The patient has been asymptomatic, and the white blood cell count has gradually increased during one-year observation, being 69.0 × 10⁹/L with 89.7% lymphocytes in August 2014.

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A 35-year-old man was referred to our hospital because of left supraclavicular and cervical lymphadenopathies. Histopathological examination of the lymph nodes revealed reactive lymphadenopathy. He visited our hospital three years after the initial diagnosis because of enlarged left cervical lymph nodes. Histopathologically, both Hodgkin/Reed-Sternberg (H/RS) and lymphocyte-predominant (LP) cells were found in the lymph node. We first suspected nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL), because these cells were CD15^- and CD30^-. However, the diagnosis of lymphocyte-rich classical Hodgkin lymphoma (LRCHL) was finally confirmed, because these cells were found to be CD20^-, Bob.1⁺, Oct.2^-, and BCL6^- by additional immunostaining. The patient was treated with six cycles of ABVD chemotherapy, and a complete response was achieved. However, he underwent autologous stem-cell transplantation after high-dose chemotherapy owing to a relapse 10 months after primary treatment. Distingushing LRCHL from NLPHL was difficult in this patient, because histopathological examination showed both H/RS and LP cells, and immunostaining revealed these cells to be triple negative (CD15^-, CD30^- and CD20^-). Accumulation of such cases are necessary to establish better criteria for the differential diagnosis and assessment of clinical behavior.

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A case of secondary acute myeloid leukemia (AML) was identified following adult T-cell leukemia/lymphoma (ATL), for which combination chemotherapy had been administered, including epipodophyllotoxin, anthracycline, and alkylating agents. AML with maturation was diagnosed by the cytological findings, cell surface markers, and chromosomal abnormalities. We previously reported two cases of AML accompanied by ATL. In this case of AML after chemotherapy for ATL, we considered that the AML was probably associated with previous chemotherapy for ATL. Although the ATL remained in remission, the therapy-related AML with complex chromosomal abnormalities proved resistant to chemotherapy, and the patient died from complications associated with AML.

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Interdigitating dendritic cell sarcoma (IDCS) is a rare and aggressive neoplasm that is thought to arise from dendritic cells. This disease usually involves the lymph nodes and, rarely, extra-nodal sites. We report a 62-year-old man presenting skin nodules in the head, body, and extremities, as well as bone marrow involvement. Morphologic analysis of a biopsied specimen from the skin lesion was consistent with IDCS. Immunohistochemical staining demonstrated that the tumor cells were positive for IDCS-associated antigens such as CD4, CD45, CD68 (KP-1), and S-100 protein. Complete remission was achieved by treatment with 6 cycles of ABVD (adriamycin, bleomycin, vinblastine, and dacarbazine) chemotherapy. Although the optimal treatment of IDSC remains unknown, the experience in the current case supports the notion that ABVD chemotherapy may be effective for IDCS, and further extends this idea to rare patients presenting multiple skin lesions.

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A 64-year-old woman had suffered from painful livedo reticularis for 2 years and was referred to us due to fever, anasarca and paresthesia of the lower limbs. Serum proteinase-3-anti-neutrophil cytoplasmic antibody (ANCA) was positive. Abnormal lymphocytes were found in the cerebrospinal fluid and bone marrow. Skin biopsy revealed large atypical lymphoid cells with CD20 positivity lodged in the small vessels and neutrophilic infiltration into the arterial vascular wall with fibrinoid degeneration. A diagnosis of intravascular large B-cell lymphoma complicated by ANCA-associated vasculitis was made, and rituximab-containing chemotherapy followed by prednisolone was quite effective for both lymphoma and ANCA-associated vasculitis.

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We report a 16-year-old male with histiocytic sarcoma (HS) originating in the lung. Partial resection of the lung was performed for a 3-cm mass with a clear boundary detected in the right inferior pulmonary lobe on a health checkup. Histologically, the tumor infiltrated into the surrounding tissue, and was comprised of spindle cells, mainly, and foam cells accompanied by mild nuclear atypia. The tumor cells were immunohistochemically positive for CD68 and CD163, indicating histiocytic lineage and the MIB-1-positive rate was low. Spindle cell morphology of HS is quite rare and only 3 cases of pulmonary HS have previously been reported.

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