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The patient, a 42-year-old man, was diagnosed as having an anterior mediastinal tumor. Examination of the resected tumor showed findings consistent with a primary thymic mucosa-associated lymphoid tissue lymphoma, stage IA. Postoperative (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography demonstrated fluorodeoxyglucose accumulation at the site of tumor excision. This accumulation was interpreted as representing a residual lesion, and the patient was treated with rituximab. The patient has since been in a state of complete remission for about 3 years. Sporadic mucosa-associated lymphoid tissue lymphoma cells that appeared to have a propensity for differentiating into plasma cells in this case were analyzed for IgG and IgG subclass expression by immunohistochemical staining. The mucosa-associated lymphoid tissue lymphoma cells that showed a propensity for differentiating into IgG-positive plasma cells were IgG3-positive and IgG1-, IgG2- and IgG4-negative. An increase in IgG3 or IgG1 expression in immune cells has been previously demonstrated in immune responses to continuous exposure to the same proteins or peptide antigens and most mucosa-associated lymphoid tissue lymphomas show increased IgG3 and/or IgG1 expression. It is consistent with the fact that inflammation due to stimulation by a pathogenic antigen is considered to be etiologically responsible for the development of mucosa-associated lymphoid tissue lymphoma.

A 39-year-old woman with a right frontal mass underwent a cranial bone tumor biopsy. Histopathologic examination of hematoxylin and eosin-stained slides showed spindle-shaped tumor cells in a storiform pattern, appearing somewhat like a sarcoma. However, the tumor cells were CD20-positive by immunohistochemical staining. Therefore, a diagnosis of spindle-shaped diffuse large B-cell lymphoma (Sp-DLBCL) was made. There have been at least 35 cases of Sp-DLBCL documented in the literature, and most were of the germinal center type, while the present case is the first report of a vimentin-positive primary Sp-DLBCL of the skull. The DLBCL in this case was immunohistochemically stained for six representative cytokines that might give rise to fibrosis, due to the evidence of fibroblastic proliferation. The DLBCL cells were positive for platelet-derived growth factor (PDGF), and some cells were also positive for tumor necrosis factor (TNF) α. Based on these findings, it was inferred that the PDGF and TNFα produced by DLBCL cells induced fibroblastic proliferation. The resultant conspicuous fibrosis caused interfibrous impingement on the DLBCL cells, which deformed them into a spindle shape. The present case is the first reported case of a PDGF-producing Sp-DLBCL.

A 22-year-old man sought medical advice for a swelling in the right side of the neck in December 2011. Histopathological examination of the lymph node biopsy initially suggested reactive lymphadenitis, on account of the only sparse presence of tumor cells. Bone marrow examination was performed in February 2012 revealed findings consistent with a diagnosis of T-cell lymphoblastic leukemia/lymphoma (T-LBL), and the patient was begun on remission induction therapy. The bone marrow showed an immature thymocytic pattern: cytoplasmic CD3+, surface CD3-, CD5+, CD4-, and CD8-. Re-assessment of the lymph node specimens revealed the same phenotype of the cells in the lymph node as that of the blasts in the bone marrow. In addition, a chromosomal aberration t(7;14)(p15;q32) was noted. The lymph node biopsy specimens were examined by paraffin-embedded tissue section-fluorescence in situ hybridization (PS-FISH), which revealed a fusion signal of T-cell receptor (TCR)γ gene (7p15) with T-cell leukemia/lymphoma 1A (TCL1A) gene (14q32.13). There have been at least 10 reported cases of T-LBL with t(7;14)(p15;q32), including the present case. However, this is the first reported case in which TCRγ-TCL1A translocation was confirmed by FISH.

A 63-year-old female suffering from hepatitis C virus infection and manic depression was admitted with a 4-month history of hoarseness. Endoscopic examination revealed the presence of a neoplasm with a smooth surface in the left supraglottic region extending to the left false vocal cord. Based on the histological findings, together with the results of systemic evaluation, the patient was diagnosed as having a mucosa-associated lymphoid tissue (MALT) lymphoma in clinical stage IE, according to the Ann Arbor classification. After one month of follow-up, the patient presented with involvement of multiple subcutaneous regions in the left neck area, etc. Biopsies revealed the same type of lymphoma as that in the supraglottis. The disease was considered to have progressed to clinical stage IV. Six courses of R-CVP (rituximab, cyclophosphamide, vincristine and prednisolone) treatment resulted in complete remission of all lesions. Primary MALT lymphoma in the larynx is extremely rare. Since the first description by Diebold et al in 1990, only 43 cases have been reported. Among these reported cases, only 7 (16%) with progressive stages were described. The R-CVP regimen appears to be effective for the treatment of progressive primary MALT lymphoma of the larynx. Furthermore, hepatitis C virus infection is thought to be closely associated with the aggressive malignant process and subcutaneous dissemination.

The patient was a 73-year-old male who came to our hospital with a chief complaint of pain and swelling of the left side of his jaw. Computed tomography revealed a mass in his left gingiva but no bone destruction. No lesions were observed at any other sites, and an incisional biopsy was performed on the gingival mass on the left side. Histologically, the mass was a diffuse large B-cell lymphoma (DLBCL), and it was CD20-positive, and CD5-negative, CD10-negative, surface immunoglobulin-negative, and Epstein-Barr virus-encoded RNA (EBER)-negative. A serum Human immunodeficiency virus (HIV)-antibody test was negative. A complete remission was achieved after 6 courses of systemic combination chemotherapy, and the complete remission has been maintained for approximately 3 years. According to the literature, primary gingival DLBCL have a high Ki-67-positive rate and many of the cases are stage I and international prognostic index low-risk. However, HIV patients have a high EBER-positive rate and a high risk of developing a CD20-negative, CD138-positive plasmablastic lymphoma, and they have a poor prognosis. By contrast, limited-stage primary gingival lymphomas whose data can be used have been rare in human immunodeficiency virus-negative patients, and only 12 cases, including our own, have ever been reported. Many of the patients have been around 65 years of age, and all of the cases have been CD20-positive, CD138-negative DLBCLs, and the CD5-negative, Epstein-Barr virus-positive rate has been low, with most cases having been non-germinal-center B-cell-like. The prognosis for relapse-free survival has been favorable.

The patient was a 52-year old woman with a history of mosquito-bite hypersensitivity since childhood. In July 2011, she developed pyrexia, headaches, and nausea, and Epstein-Barr virus (EBV)-positive aggressive natural killer leukemia (ANKL) was diagnosed on the basis of both a peripheral blood and bone marrow examination. An inguinal lymph node biopsy, on the other hand, revealed EBV-positive cytotoxic T-cell lymphoma plus the presence of a small number of EBV-positive ANKL cells, and a diagnosis of EBV-positive composite lymphoma was made. Both the cytotoxic T-cell lymphoma and ANKL exhibited EBV terminal repeat (Southern blot analysis) monoclonal patterns, and they were almost the same size, approximately 9.0 kb. If it was the identical EBV clone, it is possible that EBV infected progenitor cells common to both NK cells and T cells, that the progenitor cells then differentiated into NK cells and T cells, a chronic active Epstein-Barr virus infection developed, and neoplastic transformation occurred. If it was not the identical EBV clone, fairly similar EBVs must have infected NK cells and T cells separately, and they then underwent neoplastic transformation. Because the mechanism by which EBV infects NK cells or T cells is still unknown, we concluded that this case is also important from the standpoint of elucidating it. We are currently in the process of conducting gene analyses to determine whether the fairly similar EBVs that infected the ANKL and cytotoxic T-cell lymphoma are the identical clone.

The patient was a 72-year-old female with the chief complaint of abdominal fullness. A giant primary myoma of the uterine cervix was suspected, and total hysterectomy was performed. Based on a postoperative histopathological examination of the tumor a diagnosis of diffuse large B-cell lymphoma (DLBCL) was made in the uterus and a mass in the greater omentum was diagnosed as a marginal zone B-cell lymphoma (MZBCL). No flow-cytometry studies or chromosome or gene examinations were performed on a fresh specimen. The results of an examination of a paraffin block histopathology specimen by fluorescence in-situ hybridization (FISH) showed no mucosa associated lymphoid tissue lymphoma translocation gene 1 (MALT1) (18q21.1), B-cell lymphoma 2 (BCL2) (18q21.3), or BCL6 (3q27) split signals in either the uterus or the greater omentum, however, trisomy 18 was detected in approximately 50%-70% of the tumor cells in both the uterus and the greater omentum. Trisomy 18 was present in around 15-33% of the DLBCL cells and MZBCL cells. These findings suggested a strong possibility that the tumor cells in the uterus and greater omentum were the same clone and that transformation from MZBCL to DLBCL had occurred. Since DLBCLs that result from a transformation usually have a worse outcome than de novo DLBCLs, even when a DLBCL seems to have originated in the uterus the surrounding tissue should always be examined, and caution should be exercised in regard to transformation from a low-grade B-cell lymphoma to a DLBCL.

The patient was a 74-year-old man who was found to have a cutaneous mass on his left shoulder in February 2012. Because the mass bled easily and was tending to grow, total resection of the cutaneous tumor, which measured approximately 5 cm x 3 cm, was performed in July. Histopathological examination revealed a tumor that extended from the dermis to the cutaneous adipose tissue, but no invasion of the epidermis was seen. The tumor cells were plasmacytoid cells ranging in size from small to intermediate, and there was no nuclear irregularity. They had a high nuclear-cytoplasmic ratio, and nucleoli were observed. The tumor cells were CD4-positive, CD56-positive, and CD123-positive, and they were AE1/AE3-negative, CD3-negative, CD20-negative, and myeloperoxidase-negative. (18)F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT), a bone marrow examination, etc., were performed, but no lesions were detected at other sites. Based on the above findings a diagnosis of blastic plasmacytoid dendritic cell neoplasm (BPDCN), Stage IEA, was made. Because the patient had limited-stage BPDCN and was elderly, we treated him with a simultaneous combination of low-dose DeVIC (dexamethasone, VP16, ifosfamide, and carboplatin) therapy and local radiation therapy (LRT) and sustained a complete remission for approximately 1 year. Simultaneous combination of non-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy and LRT appeared to be useful in the treatment of limited-stage BPDCN even in the elderly.

An 85-year-old man presented with pain and numbness in the left buttock, and physical examination revealed an approximately 7 cm mass extending from the first to the third sacral vertebrae; biopsy of the mass led to the diagnosis of CD10-negative, BCL6-weakly positive, MUM1-positive, non-germinal center (non-GC) type diffuse large B-cell lymphoma (DLBCL). Furthermore, serological testing showed negative results for Epstein-Barr virus (EBV) infection, and fluorescence in situ hybridization (FISH) revealed a MYC translocation. Radiographs showed no remarkable osteolytic bone destruction, and the patient was staged with Stage IAE. After 8 cycles of rituximab therapy and 6 cycles of CHOP therapy, complete remission has been maintained until now, approximately 1 year after the treatment. Primary sacral lymphoma is very rare, with only 6 reported cases, including the present one. A review of the reported cases revealed that the disease predominantly affects elderly men, is usually non-GC-type DLBCL and stage IAE, measures approximately 2-7 cm in diameter in general, and does not show early recurrence after chemotherapy or chemoradiotherapy. There is no report in the literature yet of primary sacral DLBCL with MYC translocation, and this is the first case report. On the other hand, 35 cases of CD10-negative DLBCL with MYC translocation, including the present one, have been reported, and a review of the reported cases showed that the disease predominantly affects Asians, middle-aged or elderly men, shows positivity for either BCL6 or MUM1 and negativity for EBV, and has a high international prognostic index and poor prognosis.

Metastatic seminoma can potentially be confused with lymphoma in a lymph node biopsy. Here, we report a case in which the immunohistochemistry of CD10 was a pitfall in the differential diagnosis of a metastatic seminoma, and further present a brief study of CD10 expression in a seminoma series. A 67-year-old man, who had a history of lobectomy of the lung due to squamous cell carcinoma 2 years prior, showed lymphadenopathy of the neck and the paraaorta on follow-up study by fluorodeoxyglucose-positron emission computer tomography scan. The biopsy of the cervical node demonstrated infiltration of large atypical cells. The results of the screening immunohistochemistry were CD20(-), CD3(-), CD10(+), CD30(-), AE1/AE3(-), and placental alkaline phosphatase(-), providing the impression of CD10-positive lymphoma. However, the following studies revealed germ cell characteristics [OCT3/4(+), SALL4(+), and CLDN6(+)], confirming the diagnosis of seminoma. We further evaluated CD10 expression in a series of seminomas (n=16). Strong positivity was observed in 14 cases; partial and weak positivity, in 2 cases. These findings should be considered in the differential diagnosis of seminoma.

ALK-positive large B-cell lymphoma is a rare subtype of lymphoma, and most cases follow an aggressive clinical course with a poor prognosis. We examined an ALK-positive large B-cell lymphoma case showing an anti-ALK immunohistochemistry pattern distinct from those of 2 known ALK fusions, CLTC-ALK and NPM-ALK, for the presence of a novel ALK fusion; this led to the identification of SQSTM1-ALK. SQSTM1 is an ubiquitin binding protein that is associated with oxidative stress, cell signaling, and autophagy. We showed transforming activities of SQSTM1-ALK with a focus formation assay and an in vivo tumorigenicity assay using 3T3 fibroblasts infected with a recombinant retrovirus encoding SQSTM1-ALK. ALK-inhibitor therapies are promising for treating ALK-positive large B-cell lymphoma, especially for refractory cases. SQSTM1-ALK may be a rare fusion, but our data provide novel biological insights and serve as a key for the accurate diagnosis of this rare lymphoma.

A 53-year-old woman was referred to our hospital for further examination of a rectal polypoid lesion. Colonoscopy revealed a submucosal tumor in the rectum (Ra) and a diagnosis of MALT lymphoma was made on the histological examination of the biopsy specimens and Southern blot analysis of the immunoglobulin heavy chain gene rearrangement. Although the patient was negative for Helicobacter pylori, H. pylori eradication therapy was performed. Colonoscopy 3 months after the eradication therapy showed disappearance of the rectal tumor. H. pylori eradication appears to be a useful treatment for not only H. pylori-positive colonic MALT lymphoma but H. pylori-negative colonic MALT lymphoma.