Nobuhiko Ohnishi

Frequent MYD88 L265P and CD79B Mutations in Primary Breast Diffuse Large B-Cell Lymphoma.

Primary breast diffuse large B-cell lymphoma (PB-DLBCL) is a rare disease comprising <3% of extranodal lymphomas. It frequently reveals an activated B-cell (ABC)-like phenotype. ABC-like DLBCL was reported to have gain-of-function mutations in MYD88, CD79B, CARD11, and TNFAIP3, resulting in constitutive activation of the NF&kgr;B pathway. Because of the rare occurrence of PB-DLBCL, the frequency of MYD88 and CD79B mutations is still unknown. We used Sanger sequencing to study these mutations from 46 breast DLBCL cases and also investigated the associated clinicopathologic factors. MYD88 L265P was confirmed by allele-specific polymerase chain reaction and compared with the Sanger sequencing results. MYD88 L265P and CD79B mutations were detected in 27/46 (58.7%) and 11/33 (33.3%) cases, respectively. Twenty-eight of 46 cases met the criteria for PB-DLBCL, and the latter 18 cases were further classified as clinical breast DLBCL (CLB-DLBCL). The frequency of MYD88 L265P and CD79B mutations was 16/28 (57.1%) and 9/23 (39.1%), respectively, in PB-DLBCL and 11/18 (61.1%) and 2/10 (20%), respectively, in CLB-DLBCL. When the cutoff value was set at &Dgr;Ct⩽1, the result of allele-specific polymerase chain reaction for MYD88 corresponded to those of the Sanger sequence at 92.6% sensitivity and 100% specificity. According to Choi’s algorithm, 16/27 (59.3%) demonstrated an ABC-like phenotype in PB-DLBCL, and 15/18 (83.3%) demonstrated an ABC-like phenotype in CLB-DLBCL. In conclusion, MYD88 L265P and CD79B mutations were frequently detected in PB-DLBCL, and they may be key molecules associated with PB-DLBCL lymphomagenesis. Further analysis will be required to clarify the mechanism of its pathogenesis.

Clinicopathological features of 49 primary gastrointestinal diffuse large B‐cell lymphoma cases; comparison with location, cell‐of‐origin, and frequency of MYD88 L265P

The gastrointestinal (GI) tract is the most common primary site of extranodal diffuse large B‐cell lymphoma (DLBCL), with approximately one‐third of extranodal DLBCL occurring in the GI tract. We investigated the clinicopathological features and immunohistochemically‐assessed cell‐of‐origin of 49 GI DLBCL cases (stomach, 24; small intestine, 10; colon, 15) and also examined the presence of MYD88 L265P as recently this mutation has been frequently identified in ABC‐like DLBCL, particularly in extranodal sites. Small intestinal DLBCL was characterized by the preponderance of women (P = 0.041) and elevated LDH (P = 0.002) and soluble interleukin‐2 receptor (P = 0.033). Small intestinal DLBCL more frequently showed anemia (P = 0.031) and elevated CRP (P = 0.029) than gastric DLBCL. ABC‐like phenotype was seen in 71.4 % cases (stomach, 79 %; small intestine, 70 %; colon, 60 %). MYD88 L265P was detected in 6.1 % cases; all were primary gastric DLBCL with ABC‐like phenotype but had no distinct clinicopathological features. In conclusion, GI DLBCL had different clinicopathological features according to the primary site especially in the small intestine. Also, MYD88 L265P had little involvement in GI DLBCL compared with other extranodal DLBCLs, suggesting that its pathogenesis might be different from that of organs with a high frequency of MYD88 L265P.

CD10 down expression in follicular lymphoma correlates with gastrointestinal lesion involving the stomach and large intestine.

Follicular lymphoma (FL) shows co‐expression of B‐cell lymphoma 2 (BCL2) and CD10, whereas downexpression of CD10 is occasionally experienced in gastrointestinal (GI) FL with unknown significance. Gastrointestinal FL is a rare variant of FL, and its similarity with mucosa‐associated lymphoid tissue lymphoma was reported. We investigated the clinicopathological and genetic features of CD10 downexpressed (CD10down) GI‐FL. The diagnosis of CD10down FL was carried out with a combination of pathological and molecular analyses. The incidence of CD10down GI‐FL was shown in 35/172 (20.3%) cases, which was more frequent than nodal FL (3.5%, P < 0.001). The difference was additionally significant between GI‐FL and nodal FL when the analysis was confined to primary GI‐FL (55.2% vs 3.5%, P < 0.001). Compared to CD10+ GI‐FL, CD10down GI‐FL significantly involved the stomach or large intestine (P = 0.015), and additionally showed the downexpression of BCL6 (P < 0.001). The follicular dendritic cell meshwork often showed a duodenal pattern in the CD10down group (P = 0.12). Furthermore, a lymphoepithelial lesion was observed in 5/12 (40%) gastric FL cases, which indicated caution in the differentiation of mucosa‐associated lymphoid tissue lymphoma. Molecular analyses were undertaken in seven cases of CD10down GI‐FL, and an identical clone was found between CD10down follicles and CD10+BCL2+ neoplastic follicles. In the diagnosis of cases with CD10down BCL2+ follicles, careful examination with molecular studies should be carried out.

Frequent downregulation of BTB and CNC homology 2 expression in Epstein-Barr virus-positive diffuse large B-cell lymphoma

Diffuse large B‐cell lymphoma (DLBCL) is the most common B‐cell lymphoma subtype, and the Epstein–Barr virus (EBV)‐positive subtype of DLBCL is known to show a more aggressive clinical behavior than the EBV‐negative one. BTB and CNC homology 2 (BACH2) has been highlighted as a tumor suppressor in hematopoietic malignancies; however, the role of BACH2 in EBV‐positive DLBCL is unclear. In the present study, BACH2 expression and its significance were studied in 23 EBV‐positive and 43 EBV‐negative patient samples. Immunohistochemistry revealed BACH2 downregulation in EBV‐positive cases (P < 0.0001), although biallelic deletion of BACH2 was not detected by FISH. Next, we analyzed the contribution of BACH2 negativity to aggressiveness in EBV‐positive B‐cell lymphomas using FL‐18 (EBV‐negative) and FL‐18‐EB cells (FL‐18 sister cell line, EBV‐positive). In BACH2‐transfected FL‐18‐EB cells, downregulation of phosphorylated transforming growth factor‐β‐activated kinase 1 (pTAK1) and suppression in p65 nuclear fractions were observed by Western blot analysis contrary to non‐transfected FL‐18‐EB cells. In patient samples, pTAK1 expression and significant nuclear p65, p50, and p52 localization were detected immunohistochemically in BACH2‐negative DLBCL (P < 0.0001, P = 0.006, and P = 0.001, respectively), suggesting that BACH2 downregulation contributes to constitutive activation of the nuclear factor‐κB pathway through TAK1 phosphorylation in BACH2‐negative DLBCL (most EBV‐positive cases). Although further molecular and pathological studies are warranted to clarify the detailed mechanisms, downregulation of BACH2 may contribute to constitutive activation of the nuclear factor‐κB pathway through TAK1 activation.

Characteristic Distribution Pattern of CD30-positive Cytotoxic T Cells Aids Diagnosis of Kikuchi-Fujimoto Disease.

Introduction: Histiocytic necrotizing lymphadenitis (or Kikuchi-Fujimoto disease) frequently occurs in Asian young adult females and typically presents as cervical lymphadenopathy with unknown etiology. Although large immunoblasts frequently appear in Kikuchi-Fujimoto disease, the diffuse infiltration of these cells can cause difficulty in establishing a differential diagnosis from lymphoma. In such cases, CD30 immunostaining may be used; however, the extent or distribution pattern of CD30-positive cells in Kikuchi-Fujimoto disease remains largely unknown. Here we investigated the expression of CD30 and its clinicopathologic significance. Materials and Methods: We investigated 30 Kikuchi-Fujimoto disease and 16 control [6, systemic lupus erythematosus (SLE); 10, reactive lymphoid hyperplasia (RLH)] cases. Results: The number of CD30-positive cells in Kikuchi-Fujimoto disease was significantly more than that in SLE and RLH, and majority of these cells were located around necrotic areas. Moreover, double immunohistochemical staining showed these CD30-positive cells to be CD8-positive cytotoxic T cells, suggesting that activated cytotoxic T cells around necrotic areas are a characteristic feature of this disease. Clinicopathologic analysis showed that cases with abundant CD30-positive cells were predominantly female with only mild symptoms and normal laboratory data. Conclusions: In Kikuchi-Fujimoto disease cases, CD30-positive cytotoxic T cells were abundant around necrotic areas; this histologic feature may be helpful to differentiate this disease from SLE and RLH.