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Background: The aim of study was to determine the relative frequency of malignant lymphoma according to World Health Organization (WHO) classification in Korea. Methods: A total of 3,998 cases diagnosed at 31 institutes between 2005 and 2006 were enrolled. Information including age, gender, pathologic diagnosis, site of involvement and immunophenotypes were obtained. Results: The relative frequency of non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL) was 95.4% and 4.6%, respectively. B-cell lymphomas accounted for 77.6% of all NHL, while T/ natural killer (T/NK)-cell lymphomas accounted for 22.4%. The most frequent subtypes of NHL were diffuse large B-cell lymphoma (42.7%), extranodal marginal zone B-cell lymphoma (MZBCL) of mucosa-associated lymphoid tissue (19.0%), NK/T-cell lymphoma (6.3%) and peripheral T-cell lymphoma (PTCL), unspecified (6.3%), in decreasing order. The relative frequency of HL was nodular sclerosis (47.4%), mixed cellularity (30.6%), and nodular lymphocyte predominant (12.1%) subtypes. Compared with a previous study in 1998, increase in gastric MZBCL and nodular sclerosis HL, and slight decrease of follicular lymphoma, PTCL, and NK/T-cell lymphoma were observed. Conclusions: Korea had lower rates of HL and follicular lymphoma, and higher rates of extranodal NHL, extranodal MZBCL, and NK/T-cell lymphoma of nasal type compared with Western countries. Changes in the relative frequency of lymphoma subtypes are likely ascribed to refined diagnostic criteria and a change in national health care policy.

The development of resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) seems almost inevitable, even in patients with lung cancer that initially respond well to EGFR-TKIs. MET amplification was recently found to be a mechanism of escape from the anticancer effect of EGFR inhibitors. In the present study, we investigated the means whereby MET affects sensitivity to EGFR-TKIs in PC-9 cells. Gefitinib-or erlotinib-resistant sublines were established by exposing the parental PC-9 cell line to chronic, repeated treatments with these drugs. These resistant sublines showed more than 100-fold more resistance to gefitinib and erlotinib and acquired cross-resistance to other EGFR-TKIs. The T790M EGFR mutation was found by pyrosequencing, and this seemed to be the cause of drug resistance. Resistant cells also showed MET activation, although gene amplification was not detected. Furthermore, the induction of MET activity was not found to be associated with sensitivity to EGFR-TKIs. Interestingly, increased passage number without exposure to gefitinib or erlotinib caused MET activation, but this did not affect sensitivity to EGFR-TKIs. In addition, hepatocyte growth factor was found to block the ability of EGFR-TKIs to inhibit MET activation. However, sustained MET activation by hepatocyte growth factor did not modulate the cellular effects of gefitinib or erlotinib. Rather, activated MET enhanced migration and invasion abilities. Summarizing, MET activation may be acquired during cancer cell proliferation and enhances migratory and invasive abilities without affecting cellular sensitivity to EGFR-TKIs. Accordingly, the present study suggests that MET activation caused by factors other than MET gene amplification is not a suitable surrogate marker of resistance to EGFR-TKIs.

This study assessed the association of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection with non-Hodgkin's lymphoma in a highly HBV-endemic area. The prevalence of either HBV or HCV infection in 235 patients with non-Hodgkin's lymphoma was compared with that of an age- and sex-matched hospital control group of 235 patients. The prevalence of HBV infection was higher in B-cell non-Hodgkin's lymphoma (15.5%) than control (8.1%), but the prevalence of HCV infection in the non-Hodgkin's lymphoma patients (2.1%) and control group (3%) was similar. HBV prevalence increased significantly with age in the B-cell non-Hodgkin's lymphoma patients. The presence of HBV proteins and DNA in lymphoma tissues and peripheral blood mononuclear cells (PBMCs) from HBV-infected non-Hodgkin's lymphoma patients was also investigated using immunohistochemistry and PCR. HBV DNA was frequently detected in PBMCs from HBV-infected non-Hodgkin's lymphoma patients, but HBV antigens were not. Therefore, HBV infection, but not HCV infection, was associated with B-cell non-Hodgkin's lymphoma in Korea, suggesting a possible role for HBV in the development of non-Hodgkin's lymphoma.

Nodal marginal zone B-cell lymphoma (NMZL) is a relatively uncommon type of lymphoma. Because of the rarity, the natural history and the optimal treatment modality have not been well defined. Therefore, we performed a retrospective analysis of the clinical features and treatment outcomes of NMZL. Thirty-six patients who were histologically diagnosed as NMZL were included in the analysis. Fifty-three percent of the patients had localized disease (stages I and II), and 21.2% (7/33) had bone marrow involvement at presentation. B symptom was present in only three patients (8.3%). Most patients were categorized as low or low-intermediate risk group by international prognostic index (IPI) (77.1%). Majority (94.4%) of the patients with localized disease achieved complete remission (CR) after the initial treatment. Of the seven patients with disseminated disease, who were treated with anthracycline-based chemotherapy, four patients achieved CR. Of the seven patients who received nonanthracycline-based chemotherapy, no patient achieved CR. After the median follow-up duration of 36 months, the median progression-free survival (PFS) was 3.9 (95% CI; 2.9-5.6) years, and the estimated 5-year PFS and overall survival rates were 47.2 and 82.7%, respectively. The significant predictive factors for PFS were performance status, advanced stage, and follicular lymphoma IPI (FLIPI) in this study. This clinical feature is similar to FL rather than to MZL-MALT type.

EBV type and LMP1 variant had no significant influence on the clinicopathologic properties of tumor. However, there was a tendency toward a better survival in the EBV type B group. Histology and clinical staging were the two most important prognostic factors.

Combined inhibition of IGFR signaling enhances the growth inhibitory and apoptosis-inducing effects of gefitinib, suggesting that this approach could be useful to overcome the primary resistance to EGFR-TKIs in lung cancer.

Recently the origin of gastrointestinal stromal tumors (GISTs) is thought be the interstitial cells of Cajal or primitive stem cells. This study was performed to evaluate the roles of fine needle aspiration cytology (FNAC), cell block preparation, and immunohistochemistry in the diagnosis of GISTs. Nine cases of GIST in which FNAC was performed were included in this study. Cytologically, the tumor cells characteristically occurred in closely packed cohesive tissue fragments with high cellular density often in bloody background. The tumor cells often formed fascicles with parallel, side-by-side arrangements of the nuclei. Histologically, GISTs were highly cellular spindle or epithelioid tumor with basophilic appearance. Immunohistochemically, GISTs were c-kit positive in all of nine cases, CD34 positive in seven, focally SMA positive in two, and S-100 and GFAP negative in all. Both histologic and cell block sections showed the same histologic and immunohistochemical features. Cytomorphologically GISTs show a broad morphologic spectrum but rarely a significant nuclear pleomorphism and the assessment of malignant potential is difficult based on cytology alone. However, in the appropriate clinical and radiologic setting, a confident diagnosis of primary or metastatic GIST can be established by FNAC, cell block, and immunohistochemistry.