Diagnostic approach for classic Hodgkin lymphoma in small samples with an emphasis on PD-L1 expression and EBV harboring in tumor cells: a brief review from morphology to biology.

Classic Hodgkin lymphoma (CHL) was first described in 1832 by Thomas Hodgkin, and is characterized by a small number of Hodgkin and Reed-Sternberg cells in a rich inflammatory background. However, even in this modern era, due to the histological and biological overlap with CHL and other B-cell malignancies, including mediastinal grey zone lymphoma and other lymphomas accompanied by "Hodgkinoid cells", their discrimination is challenging and sometimes impossible. The complexity and ambiguity of the boundaries of CHL and its related diseases make the definition of CHL unresolved. Our group has studied the significance of PD-L1 expression and infection of Epstein-Barr virus (EBV) in the diagnosis of CHL, emphasizing their pathological role, clinical significance, and high reproducibility even in daily clinical practice. In this review, we summarize the diagnostic strategy of CHL and its histological lookalikes based on neoplastic PD-L1 expression and infection of EBV, and attempt a reappraisal of the definition of CHL.

Which modality is better to diagnose high-grade transformation in retroperitoneal liposarcoma? Comparison of computed tomography, positron emission tomography, and magnetic resonance imaging.

BACKGROUND: Survival in patients with retroperitoneal liposarcoma (RPLS) depends on the surgical management of the dedifferentiated foci. The present study investigated the diagnostic yield of contrast-enhanced CT, 18F-fluorodeoxyglucose positron emission tomography (PET), and diffusion-weighted MRI in terms of dedifferentiated foci within the RPLS. METHODS: Patients treated with primary or recurrent RPLS who underwent the above imaging between January 2010 and December 2021 were retrospectively reviewed. The diagnostic accuracy of the three modalities for histologic subtype of dedifferentiated liposarcoma (DDLS) and French Federation of Cancer Center (FNCLCC) grade 2/3 were compared using receiver operating characteristic curves and areas under the curves (AUCs). RESULTS: The cohort involved 32 patients with 53 tumors; 30 of which exhibited DDLS and 31 of which did FNCLCC grades 2/3. The optimal thresholds for predicting DDLS were mean CT value of 31 Hounsfield Unit (HU) (AUC = 0.880, 95% CI 0.775-0.984; p < 0.001), maximum standardized uptake value (SUVmax) of 2.9 (AUC = 0.865 95% CI 0.792-0.980; p < 0.001), while MRI failed to differentiate DDLS. The cutoff values for distinguishing FNCLCC grades 1 and 2/3 were a mean CT value of 24 HU (AUC = 0.858, 95% CI 0.731-0.985; p < 0.001) and SUVmax of 2.9 (AUC = 0.885, 95% CI 0.792-0.978; p < 0.001). MRI had no sufficient power to separate these grades. CONCLUSIONS: Contrast-enhanced CT and PET were useful for predicting DDLS and FNCLCC grade 2/3, while MRI was inferior to these two modalities.

Laminectomy triggers symptomatic growth of spinal schwannoma in a patient with schwannomatosis.

Background: Schwannomatosis (SWN) is genetically similar to neurofibromatosis type 2 (NF2) and represents a NF2 gene mutation. Previous studies have shown that these mutations in both neurons and Schwann cells can lead to the development of schwannomas after nerve crush injuries. Here, we reviewed the potential pathoanatomical mechanisms for the development of a trauma-induced spinal schwannomas in a 55-year-old male with SWN. Case Description: A 49-year-old male had originally undergone a L3-L5 lumbar laminectomy for stenosis; the schwannomas seen on the preoperative magnetic resonance imaging (MRI) were not resected. Now at age 55, he newly presented with low back pain and numbness in the left L5 dermatome, and he was diagnosed with an L4 vertebral level cauda equina tumor on MRI. Following gross-total resection, the histopathological assessment revealed a Ki-67 labeling index 5-10% in hotspots (i.e., slightly higher than the normal range of schwannomas) and a 20% mosaic loss of SMARCB1. Based on these criteria, he was diagnosed as having SWN. Conclusion: In this patient with SWN, compression/physical trauma to nerves of the cauda equina during the L3-L5 laminectomy 6 years ago likely caused the progression of schwannoma.

Clinicopathologic Analysis of Primary Adrenal Diffuse Large B-Cell Lymphoma: A Reappraisal of 23 Japanese Patients Based on EBV Association and PD-L1 Expression in Tumor Cells.

Primary adrenal diffuse large B-cell lymphoma (PA-DLBCL) is rare. We investigate 23 Japanese patients with PA-DLBCL to understand the clinicopathologic features and biological behavior of this disease. The 17 males and 6 females had a median age of 74 years (range: 40 to 86 y). Tumor cells harbored Epstein-Barr virus-encoded small RNA (EBER) in 9 (39%) samples, including samples from the 2 patients with methotrexate-associated B-cell lymphoproliferative disorder. Programmed cell death ligand 1 (PD-L1) expression was detected in tumor cells of 6 (26%) samples, including 1 EBER+ and 5 EBER- samples. Four (17%) patients exhibited an intravascular proliferating pattern, and all 4 patient samples showed positive staining for PD-L1 in tumor cells. Among those patients, 3 showed intravascular proliferating pattern accompanied by a diffuse extravascular proliferation of tumor cells, and 1 patient was diagnosed with intravascular large B-cell lymphoma. We divided the 23 patients into 3 groups: EBER+ (n=9, 39%), EBER-PD-L1+ (n=5, 22%), and EBER-PD-L1- (n=9, 39%). A comparison of the outcomes among the 3 groups showed significant differences in overall survival (P=0.034). The EBER+ group had the worst prognosis, and the EBER-PD-L1- group had the best prognosis. We also compared the outcomes among the 3 groups that received rituximab-containing chemotherapies. Both the overall survival and progression-free survival were significantly different among these groups (P<0.001 and P=0.002, respectively). In conclusion, we evaluated 3 types of PA-DLBCL and found that each had unique clinical, pathologic, and prognostic features. Our results suggested that immune senescence, iatrogenic immunodeficiency, and immune evasion contribute to the development of PA-DLBCL.

Lymphocyte-depleted classic Hodgkin lymphoma with primary extranodal disease: Two cases that highlight the combination of immunodeficiency and immune escape in the pathogenesis.

Neoplastic programmed cell death ligand 1 (PD-L1) expression, activated by PD-L1 gene alterations, is strongly associated with classic Hodgkin lymphoma (CHL). This association enabled a diagnostic consensus for lymphocyte-depleted CHL (LD-CHL), a previously enigmatic disease. We describe two patients with LD-CHL and primary extranodal disease. One patient was a 92-year-old female (Case #1) with a large mass that involved the uterus combined with swollen lymph nodes in the pelvic cavity. The second patient was a 76-year-old female (Case #2) with human T-cell leukemia virus type 1 (HTLV-1) who initially exhibited massive bone marrow involvement without peripheral lymphadenopathies. Biopsies of these tumors from the cervix uteri and bone marrow, respectively, revealed lesions rich in Hodgkin and Reed-Sternberg (H-RS) cells and diminished populations of other cell populations. Immunohistochemistry demonstrated that these H-RS cells expressed CD30, BOB1, and fascin, but not CD15, CD20, PAX5, or OCT2. They also expressed PD-L1, which led to our preferred diagnosis of LD-CHL in both patients. Epstein-Barr virus was associated with LD-CHL in Case #1, but not in Case #2. Both patients were deemed too frail for treatment. They died of disease at 1 (Case #1) and 15 months (Case #2) after the diagnosis. These findings highlight the abnormal biological behavior of this immune-escape-related lymphoid neoplasm in patients with immunodeficiency due to immune senescence and HTLV1 infection.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) immunohistochemistry for malignant lymphoma and lymphoproliferative disorders: A brief review.

The programmed cell death 1 (PD1)/PD1 ligand (PD-L1) axis plays an important role in tumor cell escape from immune control and has been most extensively investigated for therapeutic purposes. However, PD-L1 immunohistochemistry is still not used widely for diagnosis. We review the diagnostic utility of PD-L1 (by clone SP142) immunohistochemistry in large-cell lymphomas, mainly consisting of classic Hodgkin lymphoma (CHL) and diffuse large B-cell lymphoma (DLBCL). Neoplastic PD-L1 (nPD-L1) expression on Hodgkin and Reed-Sternberg cells is well-established among prototypic CHL. Of note, EBV+ CHL often poses a challenge for differential diagnosis from peripheral T-cell lymphoma with EBV+ non-malignant large B-cells; their distinction is based on the lack of PD-L1 expression on large B-cells in the latter. The nPD-L1 expression further provides a good diagnostic consensus for CHL with primary extranodal disease conceivably characterized by a combined pathogenesis of immune escape of tumor cells and immunodeficiency. Compared with CHL, the nPD-L1 expression rate is much lower in DLBCL, highlighting some specific subgroups of intravascular large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and EBV+ DLBCL. They consist of nPD-L1-positive and -negative subgroups, but their clinicopathological significance remains to be elucidated. Microenvironmental PD-L1 positivity on immune cells may be associated with a favorable prognosis in extranodal DLBCL. PD-L1 (by SP142) immunohistochemistry has helped us to understand the immune biology of lymphoid neoplasms possibly related by immune escape and/or immunodeficiency. However, knowledge of these issues remains limited and should be clarified for diagnostic consensus in the future.

Follicular T-cell lymphoma mimicking lymphocyte-rich classic Hodgkin lymphoma: a case report of a diagnostic pitfall.

Follicular T-cell lymphoma (FTCL), one of the nodal T-cell lymphomas with T follicular helper (TFH) phenotype, is an uncommon disease. The diagnosis of FTCL is challenging on the distinction from the morphological mimics mostly exemplified by follicular lymphoma. Here, we described a case of FTCL that mimicked lymphocyte-rich classic Hodgkin lymphoma (LRCHL). A 47-year-old male presented with cervical lymphadenopathy. The biopsy specimen demonstrated nodular lymphoid proliferation, which included scattered CD30+ CD15- CD20- PAX5 weakly+ Hodgkin and Reed-Sternberg (HRS)-like cells and a rich distribution of CD3+ CD4+ PD1+ T-cells. Epstein Barr virus was not detected in HRS-like cells, but it was detected in a small proportion of the scattered lymphocytes. The large cells were also negative for programmed cell death ligand 1, which appeared to be coincidental as described in our previous report of LRCHL. However, flow cytometry showed a CD3- CD4+ T-cell population that constituted 37.4% of all gated lymphocytes. A PCR analysis showed a clonal T-cell receptor-gamma gene rearrangement, but not a clonal immunoglobulin heavy chain gene rearrangement, and showed RHOA G17V mutation. The constellation of these findings led us to revise the diagnosis to FTCL. This result indicated that our case belonged to a relatively indolent subgroup of nodal peripheral T-cell lymphoma of TFH phenotype, which affects patients ≤60 years old, recently proposed by our group. This case report expands our understanding of the morphologic spectrum of FTCL and its clinicopathologic significance.

Two cases of solitary fibrous tumor/hemangiopericytoma with different clinical features according to the World Health Organization classification: case report and review of the literature.

Solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs) have been classified as one entity by the World Health Organization in 2016 due to gene fusion between NAB2 and STAT6. In the Central Nervous System (CNS), a hypocellular, collagenized tumor with a classic SFT phenotype is considered grade I, whereas more densely cellular tumors mostly corresponding to the HPC phenotype are classified as grade II or III (anaplastic) depending in mitotic count (<5 vs. >5 mitoses per 10 high-power fields). Herein, we report two cases of targeted SFT/HPC in which pathological differences and WHO grading affect clinical features. A 75-year-old woman presented with headache and had an intradural extramedullary tumor at the C1 to C2 level. The tumor was well-circumscribed and attached only to the dura mater. It was totally removed and diagnosed SFT/HPC grade I. In contrast, a 68-year-old woman presented with numbness in the right upper limb and had an intradural extramedullary tumor at the medulla to C3 levels The tumor was irregularly marginated and strongly adherent to the spinal cord and involved the vertebral artery. It was sub totally removed and diagnosed SFT/HPC grade II. To the best of our knowledge, there are only 12 cases of SFT/HPC at the craniocervical junction, including the present two cases, of which four that were adherent to the spinal cord or involved the vertebral artery were grade II or III. Although the location of the tumor was almost the same, there were significant differences in the intraoperative findings according to the WHO grading.

Histiocytic and dendritic cell neoplasms: Reappraisal of a Japanese series based on t(14;18) and neoplastic PD-L1 expression.

Histiocytic and dendritic cell (H/DC) neoplasms are heterogeneous, originating from myeloid- or stromal-derived cells. Multiple reports describe the cross-lineage transdifferentiation of neoplastic B cells into H/DC neoplasms. Most such cases are from Western countries, and rarely from Japan or East Asia. Here we report 17 cases of H/DC neoplasms in Japanese patients, with analysis of t(14;18) by fluorescence in situ hybridization, and of neoplastic programmed death-ligand 1 (PD-L1) expression by immunostaining (clones SP142, E1J2J, and 28-8). These 17 cases were diagnosed according to the 2017 World Health Organization (WHO) classification, and included two histiocytic sarcomas (HS), two interdigitating cell (IDC) sarcomas, one Langerhans cell sarcoma, two dendritic cell sarcomas, and 10 follicular dendritic cell (FDC) sarcomas. No case had any past history of follicular lymphoma (FL). Two cases of HS and one IDC sarcoma, all of which were myeloid-driven, were found to exhibit t(14;18). In the latter case, at 30 months after IDC sarcoma diagnosis, FL development was detected. Three (30%) FDC sarcoma cases exhibited neoplastic PD-L1 expression with all the three PD-L1 antibody clones. This is the first report of t(14;18) and neoplastic PD-L1 expression on H/DC neoplasms among Japanese patients, each of which appeared to be associated with HS and FDC sarcoma, respectively.

Well-differentiated fetal adenocarcinoma of the lung: positron emission tomography features and diagnostic difficulties in frozen section analysis-a case report.

BACKGROUND: Well-differentiated fetal adenocarcinoma (WDFA) of the lung is a rare disease that resembles fetal lung tubules. Most of previous reports concerning WDFA have focused on histological features, while there are few reports describing radiological features. In addition, there are no reports evaluating the difficulty of intraoperative diagnosis of WDFA with frozen section. We report a case of WDFA and review the radiological features of WDFA including the findings of F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and assess the difficulty of intraoperative diagnosis with frozen section. CASE PRESENTATION: A chest radiography performed in a 20-year-old female revealed a mass in the hilum of the right lung. Computed tomography revealed a well-defined mass measuring 3.5 × 3.0 cm in diameter in the right upper lobe, whereas PET showed a high accumulation of FDG. The most likely diagnosis was clinical T2aN0M0 stage 1B non-small cell lung cancer. A right S3 segmentectomy was performed via thoracotomy, and a benign tumor that was possibly an adenoma was intraoperatively diagnosed based on frozen section analysis. The mass was a solid tumor measuring 2.9 × 2.5 cm in diameter. Microscopically, the tumor comprised abundant glands with single or double layers of nonciliated cells and bronchial structures resembling a fetal lung. Rounded morules of polygonal cells were frequently observed. Immunohistochemistry revealed that nuclei and cytoplasm of the tumor cell were positive for ß-catenin. Finally, the postoperative pathological diagnosis was well-differentiated fetal adenocarcinoma of the lung, and completion right upper lobectomy and mediastinal lymph node dissection were conducted 1 month after the initial segmentectomy. No residual tumor or lymph node metastasis was identified, and the final pathological stage was pT1cN0M0 stage 1A3. The patient did not wish to receive any adjuvant therapy. At the 1-year follow-up, no evidence of recurrence was noted. CONCLUSIONS: Here, we report a rare case of well-differentiated fetal adenocarcinoma of the lung that was difficult to diagnose based on radiological evaluations including FDG-PET and intraoperative diagnosis using frozen section analysis.

Age-related EBV-associated B-cell lymphoproliferative disorders and other EBV + lymphoproliferative diseases: New insights into immune escape and immunodeficiency through staining with anti-PD-L1 antibody clone SP142.

Epstein-Barr virus (EBV) is prevalent among healthy individuals, and is implicated in numerous reactive and neoplastic processes in the immune system. The authors originally identified a series of senile or age-related EBV-associated B-cell lymphoproliferative disorders (LPD) bearing a resemblance to immunodeficiency-associated ones. These LPDs may be associated with immune senescence and are now incorporated into the revised 4th edition of 2017 WHO lymphoma classification as EBV-positive (EBV+) diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS). These EBV+ B-cells often have a Hodgkin/Reed-Sternberg (HRS)-like appearance and are shared beyond the diagnostic categories of mature B-cell neoplasms, mature T-cell neoplasms, classic Hodgkin lymphoma, and immunodeficiency-associated LPD. In addition, peculiar new diseases, such as EBV+ mucocutaneous ulcer and EBV+ DLBCL affecting the young, were recognized. On the other hand, lymphoma classification is now evolving in accord with deeper understanding of the biology of programmed death ligand 1 (PD-L1). Assessing PD-L1 positivity by staining with the anti-PD-L1 monoclonal antibody SP142 provides new insight by discriminating between immune evasion and senescence or immunodeficiency. The aim of the present review is to briefly summarize the diagnostic use of immunostaining with SP142 in malignant lymphomas and/or LPDs that feature tumor and nonmalignant large B-cells harboring EBV.

PD-L1 (SP142) expression in neoplastic cells predicts a poor prognosis for patients with intravascular large B-cell lymphoma treated with rituximab-based multi-agent chemotherapy.

BACKGROUND: Intravascular large B-cell lymphoma (IVLBCL) is a rare form of diffuse large B-cell lymphoma (DLBCL) arising in extranodal sites. PD-L1 expression of tumor cells has been reported in IVLBCL cells, but its clinicopathological relevance remains to be elucidated. AIMS: This study was aimed to reveal the characteristics of PD-L1+ IVLBCL. METHODS AND RESULTS: Neoplastic PD-L1 expression was examined in 34 cases of IVLBCL and clinicopathological characteristics between patients with PD-L1+ and PD-L1- IVLBCL were compared. We assessed PD-L1 expression with SP142 antibody. Twelve (35%) of 34 cases showed positivity for PD-L1. The PD-L1+ group had significantly lower survival rates compared to the PD-L1- group. The PD-L1+ IVLBCL group also had a significantly lower age distribution and a lower frequency of patients older than 60 years compared to the PD-L1- group. Very recently, we speculate that there is possible link between PD-L1+ IVLBCL and PD-L1+ extranodal DLBCL-NOS (eDLBCL) because features of the two groups showed overlapping. Therefore, we compared the clinicopathological characteristics of the PD-L1+ IVLBCL and PD-L1+ eDLBCL. There were no significant differences in clinicopathological parameters and prognosis. CONCLUSION: The worse prognosis of the PD-L1+ group might be caused by immune evasion mechanisms, which are linked to PD-L1 expression. Therefore, PD-L1+ IVLBCL cases might be regarded as good candidates for targeted immunotherapy. We also highlighted the overlapping features of PD-L1+ IVLBCL and PD-L1+ eDLBCL. This result suggests that they should be regarded as one entity, immune evasion-related extranodal large B-cell lymphoma.

PD-L1 expression on tumor or stromal cells of nodal cytotoxic T-cell lymphoma: A clinicopathological study of 50 cases.

Inhibitors of programmed cell-death 1 (PD-1) and programmed cell-death ligand 1 (PD-L1) have revolutionized cancer therapy. Nodal cytotoxic T-cell lymphoma (CTL) is characterized by a poorer prognosis compared to nodal non-CTLs. Here we investigated PD-L1 expression in 50 nodal CTL patients, with and without EBV association (25 of each). We identified seven patients (14%) with neoplastic PD-L1 (nPD-L1) expression on tumor cells, including three males and four females, with a median age of 66 years. One of the seven cases was TCRαß type, three were TCRγδ type and three were TCR-silent type. Six of the seven cases exhibited a lethal clinical course despite multi-agent chemotherapy, of whom four patients died within one year of diagnosis. Morphological findings were uniform, with six cases showing centroblastoid appearance. Among nPD-L1+ cases, two of three examined had structural variations of PD-L1 disrupting 3'-UTR region. Notably, all of the TCRγδ-type nodal CTL cases showed nPD-L1 or miPD-L1 positivity (3 and 10 cases, respectively). TCRγδ-type cases comprised 42% of nPD-L1+ cases (P = 0.043 vs. PD-L1- ), and 35% of miPD-L1+ cases (P = 0.037 vs. PD-L1- ). The results indicate that PD-L1+ nodal CTL cases, especially of the TCRγδ type, are potential candidates for anti-PD-1/PD-L1 therapies.

Reappraisal of Primary Epstein-Barr Virus (EBV)-positive Diffuse Large B-Cell Lymphoma of the Gastrointestinal Tract: Comparative Analysis Among Immunosuppressed and Nonimmunosuppressed Stage I and II-IV Patients.

Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoproliferation encompasses a broad range of clinicopathologic findings, including specific subtypes, for example, EBV mucocutaneous ulcer. Here we reassessed 36 cases of primary EBV diffuse large B-cell lymphomas (16 men and 20 women; median age, 69.5 y; range, 35 to 84 y), including 8 immunosuppressed patients (Lugano stage II-IV; median age, 74 y), 7 nonimmunosuppressed patients with stage I disease (median age, 69 y), and 21 nonimmunosuppressed patients with stage II-IV disease (median age, 69 y). All immunosuppressed patients exhibited iatrogenic immunodeficiency and an ulcerative appearance, with ulcer sites including the stomach (1 patient), small intestine (6 patients), and rectum (1 patient). Four patients were in the setting of treated lymphoma-associated immunosuppression. Immunosuppressed patients had higher incidences of intestinal involvement (P=0.001) and perforation (n=2) compared with advanced stage nonimmunosuppressed patients. Among nonimmunosuppressed stage I patients, lesions were restricted to the stomach, none showed multiple lesions or elevated serum lactate dehydrogenase, and the overall survival curve plateaued, although it was not statistically significant (P=0.0581). One nonimmunosuppressed stage I patient with a polypoid lesion exhibited spontaneous regression within 2 months after diagnosis, while another with bulky disease pursued an aggressive clinical course. Nonimmunosuppressed stage I cases without bulky masses may be considered EBV mucocutaneous ulcer with local progression. Our results demonstrated that primary EBV gastrointestinal diffuse large B-cell lymphoma could be delineated into 3 groups based on immune status and clinical stage, revealing distinguishing features useful as a pragmatic guide for diagnostic and therapeutic approaches.

Immunohistochemical Assessment of the Diagnostic Utility of PD-L1 (Clone SP142) for Methotrexate-Associated Lymphoproliferative Disorders With an Emphasis of Neoplastic PD-L1 (Clone SP142)-Positive Classic Hodgkin Lymphoma Type.

OBJECTIVES: We describe results of programmed death ligand 1 (PD-L1) immunohistochemical assessment in methotrexate (MTX)-associated lymphoproliferative disorders (LPDs) and highlight the characteristics of classic Hodgkin lymphoma (CHL) type MTX-LPD. METHODS: Fifty cases of MTX-LPD, including CHL type (n = 9), diffuse large B-cell lymphoma type (n = 15), and polymorphic B-cell LPD (n = 21), were investigated. RESULTS: Staining with anti-PD-L1 clone SP142 was exclusively found in CHL type (89%) but not in the others. Cases of CHL type MTX-LPD involved nodal disease and were associated with Epstein-Barr virus. They were histopathologically characterized by a vaguely nodular pattern, predominance of mononuclear cells, and strong expression of at least one pan-B-cell marker. Their clinical course was variable, with spontaneous regression in 5 patients, relapse in 2, and a fatal course in 1. CONCLUSIONS: The PD-L1 (clone SP142) workup aids the diagnostic approach to patients with MTX-LPD. CHL type MTX-LPD appears to represent a unique morphologic variant of CHL.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) in mediastinal composite lymphoma: A report of two cases.

Composite lymphoma is a well-known diagnostic entity exhibiting the synchronous occurrence of two or more distinct types of lymphomas in the same specimen. Here we report two patients, a 14-year-old female (Case 1) and a 45-year-old male (Case 2), with mediastinal composite lymphoma, comprising nodular sclerosis classic Hodgkin lymphoma (NSCHL) and primary mediastinal large B-cell lymphoma (PMBL). Both patients had a mediastinal mass, and manifested two different histologic components in the same biopsy, one characteristic of NSCHL and the other PMBL. The NSCHL areas included Hodgkin and Reed-Sternberg (HRS) cells with typical immunophenotypic features (CD30-positive and CD20-negative), whereas the sheets of large tumor cells characteristic of PMBL were strongly and uniformly CD20-positive. Interestingly, although both cases showed neoplastic PD-L1 (nPD-L1) positivity on the HRS cells of NSCHL, they differed regarding nPD-L1 expression on the PMBL tumor cells. In Case 1, the nPD-L1-negative PMBL component was anatomically situated outside the NSCHL lesion. On the other hand, in Case 2, the nPD-L1-positive PMBL component was characterized by transitional or continuous areas with the NSCHL component. These findings suggested that nPD-L1 expression may define two subtypes of PMBL that are more similar to or distinct from classic Hodgkin lymphoma.

Syncytial variant of classic Hodgkin lymphoma: Four cases diagnosed with the aid of CD274/programmed cell death ligand 1 immunohistochemistry.

Although several reports have highlighted neoplastic PD-L1 (nPD-L1) expression in classic Hodgkin lymphoma (CHL), some have addressed associations between its expression and detailed histopathologic features. Here we describe four cases of syncytial variant of CHL (SV-CHL), with and without Epstein-Barr virus (EBV) association, and highlight the diagnostic utility of PD-L1 (clone SP142) immunohistochemistry. The patients were a 61-year-old male, 45-year-old male, 85-year-old female, and 89-year-old female. All presented with cervical or axillary lymphadenopathy, which on biopsy had the established histopathologic features of SV-CHL with a biphasic pattern of cohesive sheets of large tumor cells and typically scattered distribution of Hodgkin and Reed-Stenberg (HRS) cells. These tumor cells showed identical immunophenotypic findings for CD15, CD30, Fascin, PAX5, OCT2, BOB1 and EBV harboring, regardless of location. The exception was absent or decreased expression of nPD-L1 from tumor cells in the confluent sheets, contrasting with HRS cell positivity in typical areas of CHL. These findings offer the first suggestion of possible downregulation of nPD-L1 expression in association with the histopathologic progression of CHL. The results may be relevant for recognizing 'confluent' sheets in the diagnostic workup for SV-CHL.

Prognostic impact of PD-L1 expression in primary gastric and intestinal diffuse large B-cell lymphoma.

BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease and the most common gastrointestinal lymphoma. The prognostic/predictive indicators among patients with gastric and intestinal DLBCL (giDLBCL) are controversial beyond their anatomical sites. We compared giDLBCL cases and investigated the clinical utility of newly emerging indicators with an emphasis on programmed cell death ligand 1 (PD-L1) expression. METHODS: This retrospective study included 174 patients with primary gastric (n = 129) or intestinal (n = 45) DLBCL treated with rituximab-containing chemotherapy between 1995 and 2018. RESULTS: Compared with gastric DLBCL (gDLBCL) cases, patients with intestinal DLBCL (iDLBCL) had a significantly higher rate of advanced Lugano stage (71% vs 37%, P < 0.001), perforation (13% vs. 0.8%, P = 0.001), PD-L1 expression on microenvironment immune cells (miPD-L1, 70% vs 46%, P = 0.008), CD10 positivity (47% vs 28%, P = 0.027), and CD5 positivity (9% vs 1.6%, P = 0.040). The iDLBCL patients showed significantly worse progression-free survival (PFS) and overall survival (OS) than gDLBCL cases (P = 0.0338 and P = 0.0077, respectively). PD-L1 expression on tumor cells was detected in only 3 (2%) of 174 cases with early relapse and/or an aggressive clinical course; whereas, miPD-L1-positive cases had significantly better OS than the miPD-L1-negative gDLBCL and iDLBCL cases (P = 0.0281 and P = 0.0061, respectively). Multivariate analysis revealed that miPD-L1 negativity (P = 0.030) was an independent adverse prognostic factor for OS in giDLBCL. CONCLUSIONS: The anatomical site of disease did not influence outcome in giDLBCL cases treated with rituximab-containing chemotherapy; while, miPD-L1 expression had a favorable impact on the outcome.

Anaplastic variant of diffuse large B-cell lymphoma: Reappraisal as a nodal disease with sinusoidal involvement.

Anaplastic variant (av) of diffuse large B-cell lymphoma (DLBCL) is morphologically defined in the 2017 World Health Organization classification, but still an enigmatic disease in its clinicopathologic distinctiveness, posing the differential diagnostic problem from gray zone lymphoma (GZL) and classic Hodgkin lymphoma (cHL). Thirty-one cases previously diagnosed as avDLBCL were reassessed. Of these, 27 (87%) and 4 (13%) were node-based and extranodal diseases, respectively. They were further reclassified into nodal avDLBCL (n = 18), nodal CD30+ DLBCL with T-cell/histiocyte-rich large B-cell lymphoma-like features (CD30+ DLBCL-THRLBCL) (n = 6), GZL with features intermediate between DLBCL and cHL (n = 3) and CD30+ extranodal DLBCL, NOS (n = 4). The nodal avDLBCL cases had a sheet-like proliferation of large cells and/or Hodgkin/Reed-Sternberg (HRS)-like cells in 12 (67%) notably with a sinusoidal pattern in 16 (89%). They showed an expression of CD20 and/or CD79a in all and CD30 in 15 of 18. All of them were negative for PD-L1 on tumor cells, although HRS-like cells showed negativity or partial loss of other B-cell markers to varying degrees. The present study highlighted the distinctiveness of the nodal avDLBCL with sinusoidal pattern, but without neoplastic PD-L1 expression, which provide refined diagnostic criteria for a more precise pathologic and clinical characterization of this disease.