Growth hormone increase by luteinizing hormone-releasing hormone reflects gonadotroph-related characteristics in acromegaly.

PURPOSE: We previously showed the clinical characteristics of acromegaly with a paradoxical growth hormone (GH) response to oral glucose or thyrotropin-releasing hormone. However, the clinical characteristics of acromegaly with an increased GH response to luteinizing hormone-releasing hormone (LHRH responders) remain unclear. The aim of the present study was to evaluate the clinical characteristics, especially gonadotroph-related characteristics of LHRH responders in acromegaly. METHODS: The clinical characteristics of 33 LHRH responders and 81 LHRH nonresponders were compared. RESULTS: No differences in age, sex or basal serum levels of GH, insulin-like growth factor-1 (IGF-1), and gonadotropin were observed between the two groups. Steroidogenic factor 1 (SF-1), gonadotropin-releasing hormone receptor (GnRHR), and LH expression was more frequently observed in LHRH responders (P < 0.05). In addition, a greater increased rate of GH after LHRH loading, and the proportion of GnRHR and gonadotropin expression was observed in pituitary tumor with SF-1 expression than that without the expression (P < 0.01). LHRH responders showed a greater GH decrease in the octreotide test and a greater IGF-1 decrease after first-generation somatostatin ligand than LHRH nonresponders (P < 0.05). Furthermore, the proportion of hypointense pituitary tumors on T2-weighted magnetic resonance imaging and tumors with densely granulated type was higher in LHRH responders than in LHRH nonresponders, respectively (P < 0.05). No difference between the two groups was observed in either somatostatin receptor 2 or 5 expression. CONCLUSIONS: The increased GH response to LHRH is associated with the gonadotroph-related characteristics. This response may reflect the biological characteristics of somatotroph tumors.

Neural-net-based cell deconvolution from DNA methylation reveals tumor microenvironment associated with cancer prognosis.

DNA methylation is a pivotal epigenetic modification that defines cellular identity. While cell deconvolution utilizing this information is considered useful for clinical practice, current methods for deconvolution are limited in their accuracy and resolution. In this study, we collected DNA methylation data from 945 human samples derived from various tissues and tumor-infiltrating immune cells and trained a neural network model with them. The model, termed MEnet, predicted abundance of cell population together with the detailed immune cell status from bulk DNA methylation data, and showed consistency to those of flow cytometry and histochemistry. MEnet was superior to the existing methods in the accuracy, speed, and detectable cell diversity, and could be applicable for peripheral blood, tumors, cell-free DNA, and formalin-fixed paraffin-embedded sections. Furthermore, by applying MEnet to 72 intrahepatic cholangiocarcinoma samples, we identified immune cell profiles associated with cancer prognosis. We believe that cell deconvolution by MEnet has the potential for use in clinical settings.

Comprehensive phenotypic and genomic characterization of venous malformations.

Venous malformations (VMs) are the most common vascular malformations. TEK and PIK3CA are the causal genes of VMs, and may be involved in the PI3K/AKT pathway. However, the downstream mechanisms underlying the TEK or PIK3CA mutations in VMs are not completely understood. This study aimed to identify a possible association between genetic mutations and clinicopathological features. A retrospective clinical, pathological, and genetic study of 114 patients with VMs was performed. TEK, PIK3CA, and combined TEK/PIK3CA mutations were identified in 49 (43%), 13 (11.4%), and 2 (1.75%) patients, respectively. TEK-mutant VMs more commonly occurred in younger patients than TEK and PIK3CA mutation-negative VMs (other-mutant VMs), and showed more frequent skin involvement and no lymphocytic aggregates. No significant differences were observed in sex, location of occurrence, malformed vessel size, vessel density, or thickness of the vascular smooth muscle among the VM genotypes. Immunohistochemical analysis revealed that the expression levels of phosphorylated AKT (p-AKT) were higher in the TEK-mutant VMs than those in PIK3CA-mutant and other-mutant VMs. The expression levels of p-mTOR and its downstream effectors were higher in all the VM genotypes than those in normal vessels. Spatial transcriptomics revealed that the genes involved in "blood vessel development", "positive regulation of cell migration", and "extracellular matrix organization" were up-regulated in a TEK-mutant VM. Significant genotype-phenotype correlations in clinical and pathological features were observed among the VM genotypes, indicating gene-specific effects. Detailed analysis of gene-specific effects in VMs may offer insights into the underlying molecular pathways and implications for targeted therapies.

Identification of invasive subpopulations using spatial transcriptome analysis in thyroid follicular tumors.

BACKGROUND: Follicular tumors include follicular thyroid adenomas and carcinomas; however, it is difficult to distinguish between the two when the cytology or biopsy material is obtained from a portion of the tumor. The presence or absence of invasion in the resected material is used to differentiate between adenomas and carcinomas, which often results in the unnecessary removal of the adenomas. If nodules that may be follicular thyroid carcinomas are identified preoperatively, active surveillance of other nodules as adenomas is possible, which reduces the risk of surgical complications and the expenses incurred during medical treatment. Therefore, we aimed to identify biomarkers in the invasive subpopulation of follicular tumor cells. METHODS: We performed a spatial transcriptome analysis of a case of follicular thyroid carcinoma and examined the dynamics of CD74 expression in 36 cases. RESULTS: We identified a subpopulation in a region close to the invasive area, and this subpopulation expressed high levels of CD74. Immunohistochemically, CD74 was highly expressed in the invasive and peripheral areas of the tumor. CONCLUSIONS: Although high CD74 expression has been reported in papillary and anaplastic thyroid carcinomas, it has not been analyzed in follicular thyroid carcinomas. Furthermore, the heterogeneity of CD74 expression in thyroid tumors has not yet been reported. The CD74-positive subpopulation identified in this study may be useful in predicting invasion of follicular thyroid carcinomas.

Ovarian high-grade serous carcinoma cells with low SMARCA4 expression and high SMARCA2 expression contribute to platinum resistance.

Platinum resistance is a major obstacle to the treatment of ovarian cancer and is correlated with poor clinical outcomes. Intratumor heterogeneity plays a key role in chemoresistance. Recent studies have emphasized the contributions of genetic and epigenetic factors to the development of intratumor heterogeneity. Although the clinical significance of multi-subunit chromatin remodeler, switch/sucrose nonfermenting (SWI/SNF) complexes in cancers has been reported, the impacts of SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4/subfamily A, member 2 (SMARCA4/A2) expression patterns in human cancer tissues have not been fully elucidated. Here, we show that low expression of SMARCA4 and high expression of SMARCA2 are associated with platinum resistance in ovarian high-grade serous carcinoma (HGSC) cells. We used fluorescence multiplex immunohistochemistry (fmIHC) to study resected specimens; we examined heterogeneity in human HGSC tissues at the single-cell level, which revealed that the proportion of cells with the SMARCA4low /SMARCA2high phenotype was positively correlated with clinical platinum-resistant recurrence. We used stable transfection of SMARCA2 and siRNA knockdown of SMARCA4 to generate HGSC cells with the SMARCA4low /SMARCA2high phenotype; these cells had the greatest resistance to carboplatin. Bioinformatics analyses revealed that the underlying mechanism involved in substantial alterations to chromatin accessibility and resultant fibroblast growth factor (FGF) signaling activation, MAPK pathway activation, BCL2 overexpression, and reduced carboplatin-induced apoptosis; these were confirmed by in vitro functional experiments. Furthermore, in vivo experiments in an animal model demonstrated that combination therapy with carboplatin and a fibroblast growth factor receptor (FGFR) inhibitor promoted cell death in HGSC xenografts. Taken together, these observations reveal a specific subpopulation of HGSC cells that is associated with clinical chemoresistance, which may lead to the establishment of a histopathological prediction system for carboplatin response. Our findings may facilitate the development of novel therapeutic strategies for platinum-resistant HGSC cells. © 2023 The Pathological Society of Great Britain and Ireland.

Myasthenia gravis-specific aberrant neuromuscular gene expression by medullary thymic epithelial cells in thymoma.

Myasthenia gravis (MG) is a neurological disease caused by autoantibodies against neuromuscular-associated proteins. While MG frequently develops in thymoma patients, the etiologic factors for MG are not well understood. Here, by constructing a comprehensive atlas of thymoma using bulk and single-cell RNA-sequencing, we identify ectopic expression of neuromuscular molecules in MG-type thymoma. These molecules are found within a distinct subpopulation of medullary thymic epithelial cells (mTECs), which we name neuromuscular mTECs (nmTECs). MG-thymoma also exhibits microenvironments dedicated to autoantibody production, including ectopic germinal center formation, T follicular helper cell accumulation, and type 2 conventional dendritic cell migration. Cell-cell interaction analysis also predicts the interaction between nmTECs and T/B cells via CXCL12-CXCR4. The enrichment of nmTECs presenting neuromuscular molecules within MG-thymoma is further confirmed immunohistochemically and by cellular composition estimation from the MG-thymoma transcriptome. Altogether, this study suggests that nmTECs have a significant function in MG pathogenesis via ectopic expression of neuromuscular molecules.

PIK3CA mutation correlates with mTOR pathway expression but not clinical and pathological features in Fibfibroipose vascular anomaly (FAVA).

BACKGROUND: Fibro-adipose vascular anomaly (FAVA) is a rare and new entity of vascular anomaly. Activating mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gene were identified at a frequency of 62.5% in FAVA cases. The PIK3CA mutations excessively activate mammalian target of rapamycin (mTOR) pathway, which promotes angiogenesis and lymphangiogenesis, implying that PIK3CA mutations may act as drivers of FAVAs. This study investigated the correlations between PIK3CA mutational status, clinicopathological features and immunohistochemical expression of the mTOR pathway in a series of FAVA. METHODS: We retrospectively evaluated the clinical and pathological findings of four FAVA cases. We performed next-generation sequencing (NGS) with a custom panel of genes associated with the mTOR pathway and genes responsible for other vascular anomalies; followed by direct sequencing and immunohistochemical analysis of the mTOR pathway. RESULTS: Two PIK3CA-mutation cases and two PIK3CA-wild-type (wt) cases exhibited similar typical clinical features of FAVA. Histological analysis revealed venous malformation, lymphatic malformation, nerves containing enlarged abnormal vessels and fibrofatty tissue were observed regardless of PIK3CA mutational status. In contrast to clinical and histological findings, the immunohistochemical expression of activated AKT and mTOR that are upstream of the mTOR pathway was detected in abnormal vessels of PIK3CA-mutation cases but not in those of PIK3CA-wt cases. However, activated eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1) and ribosomal protein S6 kinase 1 (S6K1), both of which are downstream effectors of the mTOR pathway, were expressed in abnormal vessels of both PIK3CA-mutation and PIK3CA-wt cases. Furthermore, targeting NGS did not find any common genetic mutations involved in the mTOR pathway among PIK3CA-wt cases. CONCLUSIONS: There was no significant association between the presence of PIK3CA mutations and the clinicopathological features of FAVA, suggesting that the PIK3CA gene is not necessarily involved in the onset of FAVA. FAVAs lacking PIK3CA mutations may be caused by other gene mutations that activate 4EBP1 and S6K1.

Clear Cell Carcinoma in the Oral Cavity with Three Novel Types of EWSR1-ATF1 Translocation: A Case Report.

Clear cell carcinoma (CCC) is a rare epithelial malignant tumor of the salivary glands. It is characterized by tumor cells with clear cytoplasm, hyalinized stroma, and most importantly the fusion genes EWSR1-ATF1, EWSR1-CREM, and EWSR1-PLAG1. Break-apart FISH has been performed for multiple CCC cases, but direct sequencing analysis has been performed in relatively few. Herein, we report an interesting case of CCC harboring three EWSR1-ATF1 translocations: EWSR1 exon 8-ATF1 exon 4, EWSR1 exon 7-ATF1 exon 4, and EWSR1 exon 7-ATF1 exon 5. This case indicates the possibility of independent EWSR1-ATF1 gene translocations, and could provide insight into CCC tumorgenesis.

Strong expression of PD-L1 in invasive front of MELF pattern in endometrioid carcinoma.

Endometrioid carcinoma (EC) is classified into 3 histological subtypes; Grade 1 (G1), Grade 2 (G2), and Grade 3 (G3). Although the prognosis is relatively good in G1, some G1 cases are more aggressive, which are called G1 with MELF (microcystic, elongated, and fragmented) pattern. Current therapy, such as radiotherapy and chemotherapy, is not effective in MELF, and more effective treatment is needed. The Cancer Genome Atlas (TCGA) performed an integrated genomic, transcriptomic, and proteomic analysis and classified EC into 4 groups: DNA polymerase epsilon (POLE) ultramutated, microsatellite instability hypermutated, copy-number low, and copy-number high, in which MELF was associated with microsatellite instability hypermutated. Microsatellite instability is detected in a wide variety of cancer, and PD-1 (programmed cell death 1) and PD-L1 (programmed cell death-ligand 1) are received a lot of attention as a therapeutic target. To date, no studies have been focused on PD-L1 expression in EC with MELF pattern. Then we performed immunohistochemical analysis of the distribution of PD-L1 expressing cells in G1 with MELF pattern. In cases of G1 with MELF pattern, tumor cells expressed PD-L1 significantly higher in invasive front area than in surface area. We often found lymphovascular invasion of PD-L1 expressing tumor cells. PD-L1 expressing tumor cells in MELF would be the cause of recurrence or lymph node metastasis. Moreover, in most G1 cases with MELF pattern, PD-L1 was expressed in inflammatory cells as well as tumor cells in invasive front area. PD-L1 expression in both tumor and immune cells contribute to immune suppression and both cells could be sensitive to therapeutic agents targeting the PD-L1/PD-1 axis. Therefore, significant therapeutic effect can be expected by applying PD-1/PD-L1 immunotherapy to the treatment of G1 with MELF.

Primary Alveolar Soft Part Sarcoma of Cheek: Report of a Case and Review of the Literature.

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma characterized by an alveolar or organoid arrangement of polygonal tumour cells separated by fibrovascular septa. A specific fusion gene [ASPS critical region 1 (ASPSCR1)-TFE3] was detected in ASPS. Despite being a slow-growing tumour without pain and dysfunction, ASPS is characterized by early metastasis, which leads to poor prognosis. Herein, we report a rare case of primary ASPS of the cheek harbouring ASPSCR1 (exon 7)-TFE3 (exon 5) fusion gene in a 21 year-old woman. This tumour was a well-circumscribed, smooth, round mass that was clinically suspected as a benign tumour. However, histologically, it was observed that the polygonal tumour cells were arranged in solid and alveolar growth patterns. Post-operative examination of the whole body excluded the possibility of metastasis at other sites. Thus, careful immunohistochemical and genetic analyses, as well as whole-body examination, demonstrated that the tumour was a primary ASPS of the cheek.

Usefulness of immunohistochemistry to distinguish between secretory carcinoma and acinic cell carcinoma in the salivary gland.

Secretory carcinoma (SC) of the salivary gland is a relatively newly described disease, separate from acinic cell carcinoma (ACC), which frequently displays ETV6-NTRK3 gene fusion. However, the differences between SC and ACC remain unclear. Here, histological reevaluation of 12 formerly diagnosed ACC cases was performed, which yielded a new diagnosis of SC in four cases due to a lack of obvious acinar-like cells. Immunohistochemically, phosphorylated signal transducer and activator of transcription 5 (p-STAT5) was expressed in SC but not in ACC, whereas discovered on GIST-1 (DOG1) was expressed in ACC but not in SC. Molecular analysis was possible in three SC cases, of which two showed the ETV6-NTRK3 fusion transcript on reverse-transcription polymerase chain reaction, as well as breaks in the ETV6 gene on fluorescence in situ hybridization. However, the remaining SC cases did not show this fusion transcript. Recently, several reports have suggested that SC might not be adequately diagnosed if the focus is placed solely on the ETV6-NTRK3 fusion gene due to genetic diversity. In this regard, immunohistochemistry of p-STAT5 and DOG1 is expected to be a useful alternative diagnostic tool to discriminate SC from ACC.

Clear Cell Carcinoma of Palatal Minor Salivary Gland Harboring a Novel EWSR1-ATF1 Fusion Gene: Report of a Case and Review of the Literature.

Clear cell carcinoma (CCC) is a rare low-grade malignant salivary gland carcinoma. EWSR1-ATF1 fusion has been characterized as a consistent finding in CCC, with breakpoints described between EWSR1 exon 11 and ATF1 exon 3. So far, over 100 cases of CCC harboring EWSR1 rearrangement arising from salivary gland of the oral cavity have been reported. Although EWSR1 involvement in these cases was confirmed by EWSR1 break-apart FISH indicating the translocation, sequence analysis for EWSR1-ATF1 fusion type has been reported only in three cases of CCC so far. Herein, we report a CCC case with novel EWSR1-ATF1 fusion (EWSR1 exon 15 and ATF1 exon 5) arising in minor salivary gland and review the role of the chimeric variants in some malignancies with EWSR1-ATF1 rearrangement. Current tumor was composed of the small nests of clear tumor cells and hyalized fibrous stroma. Immunohistochemically, the tumor was positive for AE1/AE3, CK5/6 and p63, negative for S100, Melan-A, SMA and CD10. After 8 months of follow-up, there are no evidence of recurrence.

Fibro-adipose vascular anomaly (FAVA): three case reports with an emphasis on the mammalian target of rapamycin (mTOR) pathway.

BACKGROUND: Fibro-adipose vascular anomaly (FAVA) is a new entity of vascular anomalies with somatic and mosaic gain-of-function mutations of the phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA). PIK3CA mutation excessively activates mammalian target of rapamycin (mTOR) pathway, which promotes angiogenesis and lymphangiogenesis. Histologically, FAVA is composed of intramuscular fibrous and adipose tissues with venous malformation (VM). Although sirolimus known as a mTOR inhibitor has good response to FAVA, expression pattern of the mTOR pathway was still unclear. Herein, we immunohistochemically investigated three novel FAVA patients with an emphasis on the mTOR pathway (p-S6K1, p-4EBP1 and p-AKT). CASE PRESENTATION: Case 1: A 10-year-old female had complained of pain in the left thigh since she was 6-year-old. Under the clinical diagnosis of VM, she underwent surgical resection for the lesion. Case 2: A 29-year-old female patient had complained of discomfort and mild pain in the left shoulder since she was 18-year-old. After childbirth, she had severe ongoing pain and contracture of the shoulder. Under clinical diagnosis of VM, surgical resection was performed. Case 3: A 53-year-old female had complained of pain and knee restriction after surgical treatment of a knee tumor at the age of 31. Under the clinical diagnosis of atypical lipomatous tumor or high grade liposarcoma, surgical resection was performed. Histologically, all three patients presented with characteristic features of fibrous and adipose tissues with abnormal vessels within the skeletal muscle, leading to diagnosis of FAVA. Although VM has been reported as an important finding in FAVA, immunohistological findings demonstrated that abnormal vessels comprised complex of VM and lymphatic malformation (LM) in all cases. Furthermore, besides vascular malformation, abnormal fibrous and adipose tissues of FAVA expressed mTOR pathway components. CONCLUSIONS: We presented three new cases of FAVA. Histological and immunohistochemical analyses revealed that VM and LM complex was an important finding in FAVA, and that the mTOR pathway components were expressed in abnormal fibrous tissue, adipose tissue and vascular malformation. These findings suggested that FAVA might be a mesenchymal malformation caused by PI3K/AKT/mTOR pathway.

Analysis of mTOR pathway expression in lymphatic malformation and related diseases.

The mammalian target of rapamycin (mTOR) inhibitor sirolimus is an effective treatment for difficult-to-treat lymphatic anomalies. However, little is known about the expression of mTOR pathway components in lymphatic anomalies. Here we investigated the expression pattern of mTOR pathway components and their phosphorylated forms (mTOR, p-mTOR, 4EBP1, p-4EBP1, S6K1 and p-S6K1) in normal lymphatic vessels and lymphatic anomalies using immunohistochemistry. We studied 18 patients of lymphatic anomalies, including lymphatic malformation (LM, n = 14), Kaposiform lymphangiomatosis (KLA, n = 2) and Kaposiform hemangioendothelioma (KHE, n = 2). Normal lymphatic vessels expressed 4EBP1, S6K1 and p-S6K1, but not p-4EBP1, mTOR or p-mTOR. The mTOR was detected in all lymphatic anomalies, whereas its activation form p-mTOR was detected in half cases of KLA and KHE but not in LM. All lymphatic anomalies expressed S6K1 and its activated form p-S6K1. The expression of 4EBP1 was also found in all lymphatic anomalies, but its activation was detected in approximately half of them. The activation of mTOR was seen in tumor (KLA and KHE) but not in malformation (LM), whereas the activation of S6K1 and 4EBP1 was seen in all and half of lymphatic anomalies, respectively.

Origin of cancer-associated fibroblasts and tumor-associated macrophages in humans after sex-mismatched bone marrow transplantation.

Cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) in tumor stroma play a key role in disease progression. Recent studies using mice models suggest that CAFs are partly derived from bone marrow and TAMs primarily originate from bone marrow-derived inflammatory monocytes. However, the origin of these cells in humans remains unclear. Hence, we investigated their human origin, using specimens from human secondary tumors that developed after sex-mismatched bone marrow transplantation, by modified immunofluorescent in situ hybridization analysis and triple immunostaining. We observed that most of the α-smooth muscle actin (αSMA)-positive CAFs in the mammary gland, liver, and oral mucosa specimens obtained 3-19 years after bone marrow transplantation are recipient-derived cells. In contrast, the majority of the peritumoral αSMA-negative fibroblast-like cells are actually bone marrow-derived HLA-DR-positive myeloid cells, such as macrophages and dendritic cells. Furthermore, almost all CD163-positive TAMs and macrophages present in the non-tumor areas are derived from bone marrow.

A case of ectopic ACTH syndrome due to DDAVP-sensitive but V1b receptor-negative bronchial typical carcinoid with lymphatic metastasis and plasma ProGRP elevation.

Ectopic ACTH syndrome (EAS) is a potentially fatal endocrine disease that results from a variety of neuroendocrine tumors (NETs), such as small cell lung cancer (SCLC) and bronchial typical carcinoid. Typical carcinoid is usually slow growing, not associated with plasma progastrin releasing peptide (ProGRP) elevation. Here, we report a 47-year-old female smoker with progressive typical carcinoid and plasma ProGRP elevation. Several types of Cushingoid features were found on physical examination. In addition, laboratory examination showed elevated plasma ACTH and serum cortisol levels. These findings indicated ACTH-dependent Cushing's syndrome. Moreover, the serum cortisol level was not suppressed by overnight high-dose dexamethasone treatment, suggesting the presence of an extra-pituitary tumor. Contrast-enhanced brain MRI revealed no pituitary adenoma, which also supported the idea that EAS occurred in the present case. Strikingly, chest computed tomographic (CT) scan showed a single 18-mm peripheral nodule in the right middle lobe of the lung. Tumor marker analysis revealed an elevation in plasma ProGRP. These data suggested a possibility that SCLC secreted ACTH and caused EAS in this patient. Of note, the plasma ACTH level was increased (1.7 fold) in l-desamino-8-D-arginine vasopressin (DDAVP) test, also suggesting the specific clinical feature in this case. After additional imaging examinations, we performed surgical resection with the suspicion of limited SCLC. As a result, pathological examination revealed a vasopressin receptor Ib (V1b) receptor-negative bronchial typical carcinoid with ACTH production and mediastinal lymphatic metastasis. In summary, we present a case of EAS caused by progressive bronchial typical carcinoid with plasma ProGRP elevation. We propose a novel subtype of lung typical carcinoid.

An unusual case of Epstein-Barr virus-positive large B-cell lymphoma lacking various B-cell markers.

BACKGROUD: Epstein-Barr virus (EBV) is associated with B-cell lymphoma in various conditions, such as immunodeficiency and chronic inflammation. We report an unusual case of EBV-positive diffuse large B-cell lymphoma (DLBCL) lacking the expression of many B-cell markers. CASE PRESENTATION: An 83-year-old man presented with a submandibular tumor. Histology of a lymph node biopsy specimen revealed diffuse proliferation of centroblast- or immunoblast-like lymphoid cells with plasmacytic differentiation. Scattered Hodgkin/Reed-Sternberg-like cells were also visible. A routine immunohistochemistry antibody panel revealed that the tumor cells were negative for B-cell and T-cell markers (i.e., CD3, CD19, CD20, CD38, CD45RO, CD79a, CD138, and Pax-5), but were positive for CD30 and MUM-1, not defining the lineage of tumor cells. The final diagnosis of EBV-positive DLBCL was confirmed based on the expression of B-cell-specific transcription factors (Oct-2 and BOB.1), PCR-based identification of monoclonal rearrangement of the immunoglobulin genes, and the presence of EBV-encoded small RNAs in the tumor cells (identified using in situ hybridization). CONCLUSION: The downregulation of broad band of B-cell markers in the present case with EBV-positive DLBCL posed a diagnostic dilemma, as the possible diagnoses included differentiation from anaplastic large cell lymphoma and CD20-negative B-cell lymphomas. Results of immunohistochemical panel including B-cell-specific transcription factors and gene rearrangement analyses critically support the correct diagnosis.

Immunohistochemical analysis of the novel marginal zone B-cell marker IRTA1 in malignant lymphoma.

Marginal zone lymphoma (MZL) is a low-grade B-cell lymphoma derived from marginal zone B cells. Because of a lack of specific immunohistochemical markers, MZL is mainly diagnosed based on the cytological appearance and growth pattern of the tumor. Marginal zone B cells were recently shown to selectively express immunoglobulin superfamily receptor translocation-associated 1 (IRTA1), but the antibody used in that study is not commercially available. We therefore investigated the IRTA1 expression in nonneoplastic lymphoid tissues and 261 malignant lymphomas, examining the ability of a commercially available antibody to accurately diagnose MZL. Among 37 MZLs, 23 of 25 extranodal MZLs of mucosa-associated lymphoid tissue (MALT lymphomas), 3 of 6 splenic MZLs and 3 of 6 nodal MZLs were positive for IRTA1. Among the 98 diffuse large B-cell lymphomas, 33 were positive for IRTA1, including 1 of 38 follicular lymphomas, and all precursor B-lymphoblastic (2/2) and T-lymphoblastic (7/7) leukemia/lymphomas. Other mature B-cell and T-cell lymphomas, and Hodgkin lymphoma were negative for IRTA1. In MALT lymphoma, positive cells were detected mainly in intraepithelial and subepithelial marginal zone B cells. In 1 case of grade 3 follicular lymphoma, IRTA1 was also expressed in the area of large cell transformation. When tumors were classified as germinal center B cell-like (GCB) or non-GCB using the algorithm of Hans, positive expression of IRTA1 was correlated significantly with non-GCB diffuse large B-cell lymphomas (P < .05). These results demonstrated the ability of the commercially available IRTA1 antibody to distinguish MALT lymphoma from other low-grade B-cell lymphomas.