A case of a pilocytic astrocytoma with histological features of anaplasia and unprecedent genetic alterations.

We report a case of pediatric glioma with uncommon imaging, morphological, and genetic features. A one-year-old boy incidentally presented with a tumor in the fourth ventricle. The tumor was completely resected surgically and investigated pathologically. The mostly circumscribed tumor had piloid features but primitive and anaplastic histology, such as increasing cellularity and mitosis. The Ki-67 staining index was 25% at the hotspot. KIAA1549::BRAF fusion and KIAA1549 partial deletions were detected by direct PCR, supported by Sanger sequencing. To the best of our knowledge, this is the first report of a glioma with both deletion of KIAA1549 p.P1771_P1899 and fusion of KIAA1549::BRAF. The tumor could not be classified using DNA methylome analysis. The present tumor fell into the category of pilocytic astrocytoma with histological features of anaplasia (aPA). Further studies are needed to establish pediatric aPA.

Increased expression of leucine-rich α-2 glycoprotein 1 as a predictive biomarker of favorable progression-free survival in meningioma.

Most meningiomas, which are frequent central nervous system tumors, are classified as World Health Organization (WHO) grade 1 because of their slow-growing nature. However, the recurrence rate varies and is difficult to predict using conventional histopathological diagnoses. Leucine-rich α-2 glycoprotein 1 (LRG1) is involved in cell signal transduction, cell adhesion, and DNA repair and is a predictive biomarker in different malignant tumors; however, such a relationship has not been reported in meningiomas. We examined tissue microarrays of histological samples from 117 patients with grade 1 and 2 meningiomas and assessed their clinical and pathological features, including expression of LRG1 protein. LRG1-high meningiomas showed an increased number of vessels with CD3-positive cell infiltration (P = 0.0328) as well as higher CD105-positive vessels (P = 0.0084), as compared to LRG1-low cases. They also demonstrated better progression-free survival (hazard ratio [HR] 0.11, 95% confidence interval [CI] 0.016-0.841) compared to LRG1-low patients (P = 0.033). Moreover, multivariate analysis indicated that high LRG1 expression was an independent prognostic factor (HR, 0.13; 95% CI, 0.018-0.991; P = 0.049). LRG1 immunohistochemistry may be a convenient tool for estimating the prognosis of meningiomas in routine practice. Further studies are required to elucidate the key role of LRG1 in meningioma progression.

Intratumoral thrombosis as a histological biomarker for predicting epidermal growth factor receptor alteration and poor prognosis in patients with glioblastomas.

PURPOSE: Intratumoral thrombosis is a specific finding in glioblastomas and considered the origin of palisading necrosis. Its distribution and contribution to the glioblastoma pathophysiology and systemic thrombosis are obscure, although deep vein thrombosis is a common complication in glioblastoma cases. METHODS: Clinicopathological and genetic analyses were performed on 97 glioblastoma tissue specimens to elucidate the role of thrombotic events and associated molecular abnormalities. RESULTS: Morphologically, intratumoral thrombosis was observed more frequently in vessels composed of single-layered CD34-positive endothelium and/or αSMA-positive pericytes in the tumor periphery, compared to microvascular proliferation with multi-channeled and pericyte-proliferating vessels in the tumor center. Intratumoral thrombosis was significantly correlated with the female sex, high preoperative D-dimer levels, and epidermal growth factor receptor (EGFR) amplification. The presence of one or more thrombi in 20 high-power fields was a predictive marker of EGFR amplification, with a sensitivity of 81.5% and specificity of 52.6%. RNA sequencing demonstrated that the group with many thrombi had higher EGFR gene expression levels than the group with few thrombi. The tumor cells invading along the vessels in the tumor periphery were positive for wild-type EGFR but negative for EGFRvIII, whereas the cells around the microvascular proliferation (MVP) in the tumor center were positive for both wild-type EGFR and EGFRvIII. Intratumoral thrombosis is an independent poor prognostic factor. CONCLUSIONS: Aberrant but exquisitely regulated EGFR can induce thrombosis in non-MVP vessels in the tumor invasion area and then promote palisading necrosis, followed by hypoxia, abnormal angiogenesis, and further tumor cell invasion.

Pediatric and elderly polymorphous low-grade neuroepithelial tumor of the young: Typical and unusual case reports and literature review.

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY), one of the pediatric-type diffuse low-grade gliomas, is characterized by a diffuse infiltrating pattern of oligodendroglioma-like tumor cells showing CD34 positivity and harbors mitogen-activated protein kinase (MAPK) alteration, such as vRAF murine sarcoma viral oncogene homolog B1 (BRAF) p.V600E or fibroblast growth factor fusion genetically. It occurs mainly in pediatric and adolescents with seizures due to the dominant location of the temporal lobe. However, there have been a few cases of PLNTY in adult patients, suggesting the wide range of this tumor spectrum. Here, we describe two cases of PLNTY, one in a 14-year-old female and the other in a 66-year-old female. The pediatric tumor showed typical clinical course and histopathology with BRAF p.V600E mutation, whereas the elderly tumor was unusual because of non-epileptic onset clinically and ependymal differentiation histopathologically harboring KIAA1549-BRAF fusion. There might be unusual but possible PLNTY, as in our elderly case. We also compared typical pediatric and unusual elderly tumors by reviewing the literature.

Clinicopathological analysis of immunohistochemical expression of immune checkpoint molecules in follicular lymphoma.

Follicular lymphoma (FL) is characterized by an indolent clinical course and a high relapse rate, and often exhibits a diffuse pattern beyond the follicular area. Our group previously reported that immune checkpoint (ICP) pathways, such as programmed cell death (PD-1) and programmed death ligand 1 (PD-L1), are poor prognostic factors for diffuse large B-cell lymphoma and adult T-cell leukemia/lymphoma. In this study, the association between the expression of multiple ICP molecules according to immunohistochemistry and clinicopathological features in FL was determined via immunostaining of 173 biopsy samples. Membrane and/or cytoplasm expression of CD86 (nCD86) and PD-L1 (nPD-L1) was found in tumor cells, whereas PD-1 (miPD-1), Galectin-9 (miGalectin-9), OX40 (miOX40), CTLA-4 (miCTLA-4), Tim-3 (miTim-3), OX40L (miOX40L), and LAG-3 (miLAG-3) were expressed in non-neoplastic stromal cells. MiPD-1 expression was significantly higher in the follicular area than in the diffuse area (p = 0.0450). Expression of miOX40 and miCTLA-4 was significantly higher in the diffuse area than in the follicular area (respectively, p = 0.0053 and p = 0.0092). MiTim-3 tended to be higher in the diffuse area than in the follicular area (p = 0.0616). MiTim-3 was significantly higher in relapse cases than in new-onset cases (p = 0.0440); miLAG-3 tended to be higher in relapse cases than in new-onset cases (p = 0.0622, not significant). The miOX40L-high FL group had a significantly worse overall survival than the miOX40L-low group (p = 0.0320). The expression of multiple ICP molecules on several cells reflects activated anti-tumor immunity and the unique FL microenvironment. Further studies on gene expression or genomic abnormalities will reveal the clinical and biological significance of ICP molecules in FL.

CD37 expression in follicular lymphoma.

CD37 is a tetraspanin protein expressed in various B-cell lymphomas that mediates tumor survival signaling. Follicular lymphoma (FL) is a representative B-cell neoplasm composed of germinal center B cells. In recent years, CD37 has been focused on as a therapeutic target for B-cell lymphoma. The purpose of this study was to characterize CD37 expression in FL patients to identify risk factors associated with various prognostic factors. We retrospectively reviewed 167 cases of FL and evaluated the immunohistochemical expression of CD37 and its statistical association with clinicopathological features. Immunohistochemically, CD37 was observed in the cytoplasm and/or membrane of neoplastic cells, mainly in neoplastic follicles to various extents. One hundred cases (100/167, 60.0%) were categorized as CD37-positive, and 67 cases were CD37-negative. In cases with high Follicular Lymphoma International Prognostic Index (FLIPI), CD37-negative cases had a poor overall survival compared with CD37-positive cases (P = 0.047), although no significant differences were observed in other clinicopathologic factors, including histological grade, BCL2-IGH translocation, and immunohistochemical phenotype. Therefore, CD37 protein may play a role in tumor progression and may serve as a therapeutic target. However, further studies are needed to explore its significance.

Elevated expression of transforming acidic coiled-coil-containing protein 3 (TACC3) reflects aggressiveness of primary central nervous system lymphomas.

Transforming acidic coiled-coil-containing protein 3 (TACC3) plays an important role in centrosome/microtubule dynamics. Deregulation of centrosomes/microtubules causes mitotic spindle defects, leading to tumorigenesis. However, the correlation between TACC3 and primary central nervous system lymphomas (PCNSLs) is unknown. The present study investigated the association between the immunohistochemical expression of TACC3, p53, and Ki-67, and the clinical factors in 40 PCNSLs. We evaluated the staining of TACC3 based on the histoscore (H-score) that contains a semiquantitative evaluation of both the intensity of staining, and the percentage of positive cells. Expression level of each component was classified as low or high according to the median H-score value. Patients with PCNSLs were divided into groups depending on TACC3 expression levels (no expression and low expression, 18; high expression, 22). Disease-free survival and overall survival of patients with high TACC3 expression were significantly shorter (p < 0.01 and p < 0.05, respectively). These results suggest that elevated expression of TACC3 could reflects aggressiveness of primary central nervous system lymphomas.

Gliosarcoma with unusual glial components: Two case reports.

Gliosarcoma is characterized by the presence of alternating lesions of glial and mesenchymal components. Although many mesenchymal components have been reported, there are few reports on glial components. We here report two cases of gliosarcoma. Case 1 was a 42-year-old woman with right hemiparesis and motor aphasia. Magnetic resonance imaging (MRI) identified a tumor in the left frontal lobe. Pathological analysis of the tumor removal specimen revealed gliosarcoma, with a glial component resembling pleomorphic xanthoastrocytoma. Postoperatively, radiotherapy and chemotherapy were conducted, and the patient was symptom-free over 12 months after surgery. Case 2 was a 67-year-old woman with a consciousness disorder and left hemiparesis. MRI revealed a tumor in the right frontal lobe. Pathological analysis of the first tumor removal specimen identified gliosarcoma, with a glial component characterized by large tumor cells. Additionally, the Ki-67 labeling index of the glial component was greater than that of the mesenchymal component, and molecular genetic analysis disclosed a mutation in the telomerase reverse transcriptase (TERT) gene (TERT). Chemotherapy and radiotherapy were performed. Four months later, MRI revealed recurrence, and the second surgery was performed. Pathological analysis revealed giant cell glioblastoma without TERT mutation. The patient died due to tumor progression 12 months after the first surgery. It is essential to continue histopathological evaluation of glial components, and further genetic evaluation on gliosarcoma is required.

Deep learning shows the capability of high-level computer-aided diagnosis in malignant lymphoma.

A pathological evaluation is one of the most important methods for the diagnosis of malignant lymphoma. A standardized diagnosis is occasionally difficult to achieve even by experienced hematopathologists. Therefore, established procedures including a computer-aided diagnosis are desired. This study aims to classify histopathological images of malignant lymphomas through deep learning, which is a computer algorithm and type of artificial intelligence (AI) technology. We prepared hematoxylin and eosin (H&E) slides of a lesion area from 388 sections, namely, 259 with diffuse large B-cell lymphoma, 89 with follicular lymphoma, and 40 with reactive lymphoid hyperplasia, and created whole slide images (WSIs) using a whole slide system. WSI was annotated in the lesion area by experienced hematopathologists. Image patches were cropped from the WSI to train and evaluate the classifiers. Image patches at magnifications of ×5, ×20, and ×40 were randomly divided into a test set and a training and evaluation set. The classifier was assessed using the test set through a cross-validation after training. The classifier achieved the highest levels of accuracy of 94.0%, 93.0%, and 92.0% for image patches with magnifications of ×5, ×20, and ×40, respectively, in comparison to diffuse large B-cell lymphoma, follicular lymphoma, and reactive lymphoid hyperplasia. Comparing the diagnostic accuracies between the proposed classifier and seven pathologists, including experienced hematopathologists, using the test set made up of image patches with magnifications of ×5, ×20, and ×40, the best accuracy demonstrated by the classifier was 97.0%, whereas the average accuracy achieved by the pathologists using WSIs was 76.0%, with the highest accuracy reaching 83.3%. In conclusion, the neural classifier can outperform pathologists in a morphological evaluation. These results suggest that the AI system can potentially support the diagnosis of malignant lymphoma.

Comprehensive immunohistochemical analysis of immune checkpoint molecules in adult T cell leukemia/lymphoma.

Acute or lymphomatous type adult T cell leukemia/lymphoma (ATLL) is an aggressive hematopoietic malignancy with poor prognosis. We previously reported that programmed cell death ligand 1 (PD-L1) expression could predict ATLL outcomes. However, the roles of other immune checkpoint molecules remain largely unknown in ATLL. Our aim in this study was to explore the clinicopathological impacts of immune checkpoint molecules in ATLL. Immunohistochemistry was performed in 69 ATLL patients with antibodies against the following: PD-L1, programmed cell death ligand 2 (PD-L2), OX40, OX40 ligand (OX40L), CD137, CD137 ligand (CD137L), Galectin-9, T cell immunoglobulin mucin-3 (Tim-3), cytotoxic T lymphocyte associated protein-4 (CTLA-4), lymphocyte activating-3 (LAG-3), CD80, CD86, glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR), GITR ligand (GITRL), and programmed death-1 (PD-1). Immune checkpoint molecules were variably expressed on neoplastic and/or microenvironmental cells. Expression of PD-1, OX40L, Galectin-9, and PD-L1 was nearly mutually exclusive on neoplastic cells, suggesting that immune checkpoint pathways differ in patients. Microenvironmental expression of PD-L1, OX40L, and Tim-3 was significantly associated with better overall survival (log-rank test; P =0.0004, 0.0394, and 0.0279, respectively). Univariate and multivariate analyses with clinical prognostic factors identified microenvironmental expression of PD-L1 and OX40L, and age (> 70 years) as significant prognostic factors. This is the first comprehensive analysis of ATLL immune checkpoint molecules. Our results may provide information on new therapeutic strategies in ATLL.

RHOA mutation in follicular T-cell lymphoma: Clinicopathological analysis of 16 cases.

Follicular T-cell lymphoma (FTCL) is considered to originate from follicular helper T-cell (Tfh) cells. Angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphomas with the Tfh phenotype, derived from Tfh cells, often harbor RHOA G17V mutation. We investigated whether RHOA mutations affect the clinicopathological features of FTCL. We performed deep sequencing and Sanger sequencing for RHOA exon 2 in 16 cases of FTCL. Nine cases showed RHOA mutations, including eight with c.G50T, p.Gly17Val and one with c.G50A, p.Gly17Glu, c.A52G, p.Lys18Glu, c.T102C, p.Tyr34Tyr and c.G145T, p.Asp49Tyr. Compared to the RHOA mutation-negative group, the RHOA mutation-positive group had a higher tendency for B-immunoblasts (P = 0.06), the AITL component (P = 0.09), and higher positive rate for CD10 (P = 0.09) and BCL6 (P = 0.09), and a significantly higher positive rate for CXCL13 (P = 0.04). Although not statistically significant, the RHOA mutation-positive group showed higher values for almost all characteristic AITL features. There was no significant difference in overall survival between RHOA mutation-positive and -negative groups. The RHOA mutation may play an important role in clinicopathological characteristics and lymphomagenesis of FTCL. A more detailed investigation is needed to highlight the importance of RHOA mutations in FTCL.

Human leukocyte antigen class II expression is a good prognostic factor in adult T-cell leukemia/lymphoma.

Attenuated human leukocyte antigen (HLA) class I expression is implicated as a major immune escape mechanism in several types of tumor. We previously reported that HLA class I/ß2 microglobulin and programmed death ligand-1 expression are prognostic factors in adult T-cell leukemia/lymphoma. A recent report suggested that HLA class II expression is also an important prognostic factor for the clinical outcome of programmed death-1 blockade therapy in recurrent/refractory Hodgkin lymphoma. This prompted us to evaluate HLA class II expression in adult T-cell leukemia/lymphoma and to compare the findings with the patients' clinicopathological features. Of the 132 biopsy specimens examined from newly diagnosed patients, lymphoma cells were positive for HLA class II expression in 44 patients (33.3%), whereas programmed death ligand-1 expression was observed on neoplastic cells from nine patients (6.9%) and on stromal cells in the tumor microenvironment in 83 cases (62.9%). HLA class II-positive cases showed a significantly better overall survival compared to the HLA class II-negative cases (P<0.0001). Patients positive for HLA class II and programmed death ligand-1 microenvironmental expression had significantly better prognosis than the other groups (P<0.0001). HLA class II-positive and HLA class II-negative groups also showed a significant difference in complete remission rate (P=0.0421), HLA class I/ß2 microglobulin expression (P=0.0165), and the number of programmed death-1-positive tumor infiltrating cells (P=0.0020). HLA class II expression was a prognostic factor for overall survival both in univariate and multivariate analyses (P<0.0001 and P=0.0007, respectively). Our study reveals that HLA class II is a novel prognostic factor in adult T-cell leukemia/lymphoma.

Clinicopathological analysis of CD47 and signal regulatory protein alpha expression in myeloid sarcoma patients: CD47 expression is a favourable prognostic factor.

Myeloid sarcoma is a rare extramedullary haematopoietic malignancy. Interaction between CD47 and signal regulatory protein α (SIRPα) inhibits phagocytosis. CD47-positive tumours confer poor prognoses in various malignant tumours, including acute myeloid leukaemia. This study aimed to investigate the clinicopathological effects of CD47 and SIRPα expression in myeloid sarcoma. Immunohistochemistry (IHC) of CD47 and SIRPα was performed in 84 biopsy samples obtained from patients with myeloid sarcoma, some of which were CD47-positive. Patients were categorised into the following two groups based on IHC of SIRPα: those with SIRPα-positive neoplastic cells (nSIRPα) and, SIRPα expression on non-neoplastic stromal cells in tumour microenvironment (miSIRPα). In addition, patients with CD47 positivity had higher lymphocytic infiltration into the tumour microenvironment. Overall, these patients had significantly higher overall survival, however, no significant difference was observed in progression-free survival. No significant prognostic differences were observed between the nSIRPα and miSIRPα groups. This is the first study to demonstrate an association between CD47 expression and improved prognosis in myeloid sarcoma. Nonetheless, it will be necessary to conduct additional research on gene expression and genomic abnormalities to elucidate the corresponding pathogenesis of myeloid sarcoma.

Co-expression of regulatory B-cell markers, transforming growth factor ß and interleukin-10 as a prognostic factor in diffuse large B-cell lymphoma.

Regulatory B cells (Bregs) suppress antitumor immunity by producing anti-inflammatory cytokines such as transforming growth factor ß (TGF-ß) and interleukin-10 (IL-10) and promoting tumor growth. It is unknown whether diffuse large B-cell lymphoma (DLBCL), a common subtype of B-cell malignancy, exhibits characteristics similar to those of Bregs. This study aimed to clarify the features of DLBCLs carrying Breg markers. In 123 DLBCL cases, we evaluated TGF-ß and IL-10 expression in tumor biopsy samples using immunohistochemical staining and retrospectively analyzed their clinicopathological characteristics. Fifteen cases (12.2 %) classified as Breg-type DLBCL were positive for both TGF-ß and IL-10. Breg-type DLBCL is mainly classified as having activated B cell-like cells of origin. Breg-type DLBCL cases showed significantly worse progression-free survival and overall survival (OS) than other DLBCL cases (P = 0.0016 and P = 0.042, respectively). In multivariate analysis, Breg-type DLBCL significantly affected OS (hazard ratio, 3.13; 95 % confidence interval 1.15-8.55; P = 0.025). Gene expression analysis showed that the expression of follicular dendritic cell-associated genes (FCER2, PIK3CD, FOXO1) was downregulated in Breg-type DLBCLs compared to other DLBCLs. These results suggest that the double expression of Breg markers, TGF-ß and IL-10, in tumor cells indicates a poor prognosis in DLBCL patients. Further studies evaluating genomic abnormalities could confirm the characteristics of Breg-type DLBCL.

Clinicopathological comparison between PTCL-TBX21 and PTCL-GATA3 in Japanese patients.

AIM: Peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) is a heterogeneous disease that can be classified into the PTCL-TBX21 and PTCL-GATA3 subtypes. METHODS: In this study, we compared the clinicopathological features of PTCL-NOS in a Japanese cohort, classified using an IHC algorithm. RESULTS: One hundred patients with PTCL-NOS were categorized as having PTCL-TBX21 (n = 55), PTCL-GATA3 (n = 24), or PTCL-unclassified (n = 21). When comparing PTCL-TBX21 and PTCL-GATA3, PTCL-TBX21 showed significantly lower CD4 positivity (p = 0.047), lower counts of high endothelial venules (p = 0.032), and a tendency for a better response to initial treatment (p = 0.088). Gene expression analysis using the nCounter system showed higher expression of tumor immunity-related genes, such as PD-L1, LAG3, and IDO1, in PTCL-TBX21 than in PTCL-GATA3. PTCL-GATA3 had significantly worse overall survival (OS) than those with PTCL-TBX21 (p = 0.047), although a similar tendency was observed for progression-free survival (PFS) (p = 0.064). PTCL-GATA3 was a prognostic factor for OS in univariate analysis (HR 2.02; 95% CI, 1.09-3.77; p = 0.027), although multivariate analysis did not show significance (HR 2.07; 95% CI, 0.93-4.61; p = 0.074). In the PFS analysis, PTCL-GATA3 was an independent prognostic factor by univariate analysis (HR 1.96; 95% CI, 1.08-3.56; p = 0.027) and multivariate analysis (HR 2.34; 95% CI, 1.07-5.11; p = 0.032). CONCLUSION: The classification of PTCL-NOS into PTCL-TBX21 and PTCL-GATA3 is useful for predicting the prognosis of Japanese patients and stratifying the administration of tumor immune checkpoint inhibitors in clinical practice.

Digital spatial profiling of CD4+ T cells in classic Hodgkin lymphoma.

Classic Hodgkin lymphoma (CHL) harbors a small number of Hodgkin-Reed-Sternberg (HRS) cells scattered among numerous lymphocytes. HRS cells are surrounded by distinct CD4+ T cells in a rosette-like manner. These CD4+ T cell rosettes play an important role in the tumor microenvironment (TME) of CHL. To elucidate the interaction between HRS cells and CD4+ T cell rosettes, we completed digital spatial profiling to compare the gene expression profiles of CD4+ T cell rosettes and other CD4+ T cells separated from the HRS cells. Immune checkpoint molecules including OX40, programed cell death-1 (PD-1), and cytotoxic T lymphocyte associated protein 4 (CTLA-4) expression was higher in CD4+ T cell rosettes compared to other CD4+ T cells. Immunohistochemistry confirmed variable PD-1, CTLA-4, and OX40 expression in the CD4+ T cell rosettes. This study introduced a new pathological approach to study the CHL TME, and provided deeper insight into CD4+ T cells in CHL.

Case-based similar image retrieval for weakly annotated large histopathological images of malignant lymphoma using deep metric learning.

In the present study, we propose a novel case-based similar image retrieval (SIR) method for hematoxylin and eosin (H&E) stained histopathological images of malignant lymphoma. When a whole slide image (WSI) is used as an input query, it is desirable to be able to retrieve similar cases by focusing on image patches in pathologically important regions such as tumor cells. To address this problem, we employ attention-based multiple instance learning, which enables us to focus on tumor-specific regions when the similarity between cases is computed. Moreover, we employ contrastive distance metric learning to incorporate immunohistochemical (IHC) staining patterns as useful supervised information for defining appropriate similarity between heterogeneous malignant lymphoma cases. In the experiment with 249 malignant lymphoma patients, we confirmed that the proposed method exhibited higher evaluation measures than the baseline case-based SIR methods. Furthermore, the subjective evaluation by pathologists revealed that our similarity measure using IHC staining patterns is appropriate for representing the similarity of H&E stained tissue images for malignant lymphoma.

Expression of telomerase reverse transcriptase in peripheral T-cell lymphoma.

Telomere length is maintained by the activation of telomerase, which causes continuous cell division and proliferation in many carcinomas. A catalytic reverse transcriptase protein (TERT) encoded by the TERT gene plays a critical role in the activation of telomerase. We performed a molecular and pathological analysis of the TERT against three different peripheral T-cell lymphoma (PTCL) subtypes: PTCL, not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), and adult T-cell leukemia/lymphoma (ATLL). Immunohistochemical analysis demonstrated TERT expression in 31% of AITL, 11% of PTCL-NOS, and 5% of ATLL. Among them, AITL frequently showed high TERT expression with statistical significance. TERT promoter mutation analysis and genomic copy number evaluation were performed. TERT promoter mutation was observed in two cases of PTCL-NOS (2/40) and not in other PTCLs. Genome copy number amplification was detected in 33% of PTCL-NOS, 33% of AITL, and 50% of ATLL cases. We evaluated the relationship between the analyzed TERT genomic abnormalities and protein expression; however, no apparent relationship was observed. Furthermore, immunostaining showed TERT expression in the PTCL cytoplasm, suggesting the existence of mechanisms other than the maintenance of telomere length. Statistical analysis of the effect of TERT expression on the prognosis in PTCL cases revealed that TERT expression tended to have a poor prognosis in PTCL-NOS. Since TERT expression was not an independent factor in multivariate analysis, further research will be needed to clarify the poor prognosis of PTCL-NOS in TERT expression.