Immunohistochemical Evaluation of FLI-1 in Acute Lymphoblastic Lymphoma (ALL): A Potential Diagnostic Pitfall

FLI-1 is expressed in a wide variety of hematolymphoid neoplasms: a special concern in the differential diagnosis

Friend Leukemia Virus Integration 1 (FLI-1) is a member of E26 transformation-specific family of transcription factors that participates in hematopoietic and vascular endothelial cell development. Immunohistochemical detection of FLI-1 has been widely used to diagnose vascular tumors or, more evidently, Ewing's sarcoma. However, the expression pattern of FLI-1 in hematolymphoid neoplasms remains unclear. Therefore, in this study, we aimed to investigate the expression of FLI-1 in these tumors, focusing on high-grade lesions, which presents a diagnostic challenge by mimicking Ewing's sarcoma. We evaluated the expression FLI-1 in various types of lymphoid and plasmacytic tumors, including 27 plasmablastic lymphomas, 229 diffuse large B-cell lymphomas, 22 precursor T- or B-lymphoblastic lymphomas, 24 angioimmunoblastic-type nodal T-follicular helper cell lymphomas, 52 peripheral T-cell lymphomas, NOS, 18 Burkitt lymphomas, 18 non-gastric lymphomas of mucosa-associated lymphoid tissue, 38 chronic lymphocytic leukemia/small lymphocytic lymphomas, 15 mantle cell lymphomas, 23 gastric MALT lymphomas, 50 plasma cell myelomas, and 38 follicular lymphomas. We calculated the H-scores of FLI-1 immunostaining, ranging from 0 to 200, and used the scores to analyze the clinicopathological significance of FLI-1 statistically. FLI-1 was expressed to varying degrees in all types of hematological tumors. FLI-1 expression was detected in 84.1% of patients (466/554). FLI-1 was highly expressed in precursor T- or B-lymphoblastic lymphomas. Follicular lymphomas exhibited low FLI-1 expression. In plasmablastic lymphoma, 85.2% of the patients were focally positive for FLI-1. FLI-1 expression did not correlate with clinicopathological variables, such as demographic data or disease stage, in patients with plasmablastic lymphoma and diffuse large B-cell lymphoma. However, FLI-1 overexpression was associated with poorer overall survival in patients with plasmablastic lymphoma. This study demonstrates that FLI-1 is expressed in various hematolymphoid neoplasms. FLI-1 expression can lead to diagnostic confusion, especially in small blue round cell tumors, such as lymphoblastic lymphoma, plasmablastic lymphoma, and plasma cell myeloma, when distinguishing tumors positive for CD99 and CD56 without CD3, CD20, or CD45. Our findings also suggested the possibility of FLI-1 as a potential prognostic biomarker for plasmablastic lymphoma.

FLI1 and MIC2 expression in precursor B-lymphoblastic leukemia with Burkitt-like morphology and extensive extramedullary involvement: A diagnostic challenge in pediatric small round cell tumor

Pediatric small round cell tumors (PSRCTs) constitute a large proportion of childhood malignancies with overlapping diagnostic and clinical features but radically different therapies. Here, we report a case of 16-year-old male child presenting with diffuse abdominal and mediastinal mass, axillary lymphadenopathy, and pleural effusion. Bone marrow aspirate showed near total replacement by small round malignant cells. The bone marrow biopsy showed interstitial infiltration by malignant cells, which were CD45- CD3- CD20- MIC2+ FLI1+ and diagnosis of Ewing's sarcoma was established. In contrast, flowcytometric immunophenotyping of the bone marrow aspirate showed CD45- cells, which were CD19+ cytCD79a+ CD10+ CD81+ CD38+ HLA-DR+ CD22+ CD20- consistent with B-cell acute lymphoblastic leukemia (B-ALL). The extended immunostaining panel on bone marrow biopsy also showed positivity for cytCD79a, CD10, CD19, and BCL-2, whereas fluorescent in-situ hybridization for EWSR1 gene rearrangement was negative. Thus, a final diagnosis of CD45- FLI1+ MIC2+ B-ALL was established. Rare cases of CD45- B-ALL with immunoreactivity for MIC2 and Friend leukemia virus integration 1 (FLI1) have posed a diagnostic challenge for PSRCTs in the recent past. This case report highlights the role of multimodality approach in establishing a correct diagnosis in CD45- PSRCTs to ensure definitive therapy and better clinical outcome.

ZBTB16: A new biomarker for primitive neuroectodermal tumor element / Ewing sarcoma

Primitive neuroectodermal tumor (PNET) traditionally encompasses two different classes of tumors with similar morphology - PNET of the peripheral nervous system (pPNET) and PNET of the central nervous system (cPNET). The latter also includes germ cell tumor-derived PNET (gPNET). There are currently no specific markers for gPNET. This study seeks to investigate the expression of ZBTB16 in PNET and other small round blue cell tumors as well as its potential diagnostic utility. Immunohistochemical expression of the ZBTB16 was studied in a total of 27 PNETs (12 pPNETs, 8 cPNETs, 3 primary testicular gPNETs, and 4 metastatic gPNETs) and 38 small round blue cell tumors. Positive expression for ZBTB16 was seen diffusely in 9/12 (75%), moderately in 2/12 (17%) and focally in 1/12 (8%) of pPNETs, diffusely in 3/7 (43%) and moderately in 4/7 (57%) of gPNETs, and diffusely in 2/8 (25%), moderately in 2/8 (25%) and focally in 4/8 (50%) of cPNETs. Whereas, all of the 38 non-PNET small round blue cell tumors were nonreactive. The results suggest that ZBTB16 is a highly sensitive and specific biomarker for both pPNET and gPNET/cPNET. ZBTB16 effectively differentiates PNETs from other small round blue cell tumor mimics, including the two most common germ cell tumor-derived somatic malignancies - rhabdomyosarcoma and nephroblastoma. Of note, compared to the expression of ZBTB16 in pPNET/Ewing sarcoma and gPNET, the expression of ZBTB16 in cPNET was more variable, which appears consistent with the heterogeneity of cPNET. The close proximity of ZBTB16 and FLI-1 genes on chromosome 11q may explain the overexpression of ZBTB16 in PNET, especially in pPNET with t(1122) translocation.

Extraskeletal Ewing's sarcoma/peripheral primitive neuroectodermal tumor of the small bowel presenting with gastrointestinal perforation

Extraskeletal Ewing’s sarcoma (E-EWS)/peripheral primitive neuroectodermal tumor (pPNET) is a rare soft tissue tumor that arises from a multipotent progenitor cell and is considered to be of neuroectodermal origin. Although soft tissue E-EWS/pPNETs are common, they are exceedingly rare in the small bowel. Only 30 cases of E-EWS/pPNET of the small bowel have been reported. However, only one case of gastrointestinal perforation has been reported till today. Here, we report the second case of E- EWS/pPNET with gastrointestinal perforation.

Practical Application of Cytology and Core Biopsy in the Diagnosis of Mesenchymal Tumors

Soft tissue neoplasms are increasingly being sampled by core needle biopsy and fine-needle aspiration (FNA), and these small biopsy specimens pose unique diagnostic challenges. Many advances in ancillary testing enable detection of characteristic immunophenotypes and molecular alterations, allowing accurate classification of soft tissue tumors in these small biopsy samples. This review outlines pattern-based diagnostic approaches to core biopsies and FNAs of soft tissue neoplasms, including formulation of practical differential diagnoses and relevant application of ancillary tests.

Comprehensive analysis of multi Ewing sarcoma microarray datasets identifies several prognosis biomarkers

Ewing sarcoma (ES) is a common primary malignancy in children and adolescents. Progression of treatment methods hasn't contributed a lot to the imrovement of prognosis. To identify potential prognostic biomarkers, a meta-analysis pipeline of multi-gene expression datasets for ES from the Gene Expression Omnibus (GEO) was performed. Three datasets were screened and differential expression genes (DEGs) in ES samples compared with normal tissues were identified through limma package and subjected to network analysis. As a result, 1,470 DEGs were obtained which were mainly involved in biological processes associated with immune response and transcription regulation. Network analysis obtained 22 core genes with high network degree and fold change. Kaplan-Meier analysis based on ES datasets from The Cancer Genome Atlas identified five genes, including glycogen phosphorylase, muscle-associated, myocyte-specific enhancer factor 2C, tripartite motif containing 63, budding uninhibited by benzimidazoses1 and Ras GTPase-activating protein 1, whose altered expression profiles are significantly associated with survival. Changes of their expression values were further confirmed through RT-qPCR in ES cell and normal cell lines. Those genes may be considered as potential prognostic biomarkers of ES and should be helpful for its early diagnosis and treatment.

Cytodiagnosis of Extraskeletal Ewing's Sarcoma and its Confirmation by Fluorescence in situ Hybridization

Extraskeletal Ewing's sarcoma is an aggressive malignant small round cell tumour usually occuring in children and adolescents. It needs to be differentiated from other malignant small round cell tumours and immunohistochemistry plays a pivotal role in establishing the diagnosis. Fluorescence in situ hybridization or real time-polymerase chain reaction helps in confirming the diagnosis by demonstration of EWS-FLI1 translocation, which is found in approximately 85% of the cases. We report a case of extraskeletal Ewing's sarcoma in a10-year-old male, who presented with a right gluteal region mass. Fine needle aspiration and cell block preparation followed by a panel of immunohistochemical markers were performed. Immunohistochemistry for CD99 and FLI1 was positive. EWS-FLI1 translocation was confirmed by fluorescence in situ hybridization.

Ewing sarcoma: a chronicle of molecular pathogenesis

Sarcomas have traditionally been classified according to their chromosomal alterations regardless of whether they accompany simple or complex genetic changes. Ewing sarcoma, a classic small round cell bone tumor, is a well-known mesenchymal malignancy that results from simple sarcoma-specific genetic alterations. The genetic alterations are translocations between genes of the TET/FET family (TLS/FUS, EWSR1, and TAF15) and genes of the E26 transformation-specific (ETS) family. In this review, we intend to summarize a chronicle of molecular findings of Ewing sarcoma including recent advances and explain resultant molecular pathogenesis.

SEPTIN2 and STATHMIN Regulate CD99-Mediated Cellular Differentiation in Hodgkin's Lymphoma

Hodgkin’s lymphoma (HL) is a lymphoid neoplasm characterized by Hodgkin’s and Reed-Sternberg (H/RS) cells, which is regulated by CD99. We previously reported that CD99 downregulation led to the transformation of murine B lymphoma cells (A20) into cells with an H/RS phenotype, while CD99 upregulation induced differentiation of classical Hodgkin’s lymphoma (cHL) cells (L428) into terminal B-cells. However, the molecular mechanism remains unclear. In this study, using fluorescence two-dimensional differential in-gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), we have analyzed the alteration of protein expression following CD99 upregulation in L428 cells as well as downregulation of mouse CD99 antigen-like 2 (mCD99L2) in A20 cells. Bioinformatics analysis showed that SEPTIN2 and STATHMIN, which are cytoskeleton proteins, were significantly differentially expressed, and chosen for further validation and functional analysis. Differential expression of SEPTIN2 was found in both models and was inversely correlated with CD99 expression. STATHMIN was identified in the A20 cell line model and its expression was positively correlated with that of CD99. Importantly, silencing of SEPTIN2 with siRNA substantially altered the cellular cytoskeleton in L428 cells. The downregulation of STATHMIN by siRNA promoted the differentiation of H/RS cells toward terminal B-cells. These results suggest that SEPTIN2-mediated cytoskeletal rearrangement and STATHMIN-mediated differentiation may contribute to changes in cell morphology and differentiation of H/RS cells with CD99 upregulation in HL.

Immunohistochemistry as potential diagnostic pitfall in the most common solid tumors of children and adolescents

Making a correct diagnosis when dealing with a small round blue cell tumor (SRBCT) of children and adolescents may be relatively straightforward if the tumor arises in the typical clinical setting and the classic pathologic features are all recognizable. However it is widely known that diagnostic difficulties may arise because of: (i) many tumors share overlapping morphological and/or immunohistochemical features; (ii) considerable clinical, pathologic, and immunohistochemical variations do exist; (iii) the increasing use of small biopsies in daily practice makes the diagnosis of these neoplasms more challenging. Accordingly, immunohistochemical analyses are currently mandatory in establishing the correct diagnosis. In this regard there is the need to identify more sensitive and specific immunomarkers useful in the distinction of the several tumor entities. Over the last decades, several markers, such as CD99, WT1 protein, desmin, myogenin, NB84, and INI1 have been identified, providing a considerable help in recognition of the most common solid tumors (ESW/pPNET, rhabdomyosarcoma, neuroblastoma, Wilms' tumor, desmoplastic small round cell tumor; malignant rhabdoid tumor) in children and adolescents. However, at the same time, their unusual, unexpected expression can result in a misinterpretation of the immunohistochemical results, especially by pathologists who are not familiar with oncologic pediatric pathology. Therefore the present review focuses on the potential immunohistochemical pitfalls which should be kept in mind by pathologists to prevent diagnostic errors when dealing with SRBCTs.

[Value of core needle biopsy in preoperative diagnostics of soft tissue tumors: possibilities and limitations]

The differential diagnosis of soft tissue swellings encompasses a variety of benign, intermediate, low-grade malignant and high-grade neoplastic lesions in addition to tumor-like reactive processes. As treatment of these heterogeneous conditions varies greatly from conservative observation and simple local excision up to extensive radical surgical resection, treatment decisions are based mainly on a precise preoperative histological diagnosis on limited biopsy material. Even for clinically unequivocal sarcomas, the importance of the preoperative histological diagnosis has been increasingly emphasized as different therapeutic regimens have been established for different sarcoma types and the indications for preoperative treatment is influenced by the tumor grade and by the entity itself. Other factors positively influencing the increasing use of core needle biopsy for preoperative tumor diagnosis in soft tissue pathology are the availability of modern high-resolution imaging modalities as well as the establishment of several new second generation immunohistochemical markers and the discovery of entity-specific translocations detected by fluorescence in situ hybridization (FISH) in several sarcoma subtypes. In this review it will be shown that a targeted approach for processing core needle biopsies oriented towards the characteristic topographical, demographic, cytomorphological and architectural features of soft tissue lesions facilitates a precise diagnosis of soft tissue neoplasms in most cases. However, profound knowledge of the different aspects of soft tissue tumor diagnostics and familiarity with the frequent as well as the less common and rare tumor entities and variants is a prerequisite for appropriate interpretation of core needle biopsy findings and for selecting a limited but well-suited marker panel. The utilization of modern immunohistochemistry and/or FISH methods is highly useful for establishing the diagnosis of rare and unusual neoplasms in core needle biopsies.

Round cell tumors of bone: an update on recent molecular genetic advances

Round cell tumors of bone are a divergent group of neoplasms that largely constitute Ewing sarcoma/primitive neuroectodermal tumor, small cell osteosarcoma, Langerhans cell histiocytosis, mensenchymal chondrosarcoma, and hematopoietic malignancies including lymphoma and plasmacytoma/myeloma, along with metastatic round cell tumors including neuroblastoma, rhabdomyosarcoma, and small cell carcinoma. These lesions share many histomorphologic similarities and often demonstrate overlapping clinical and radiologic characteristics, but typically have a diverse clinical outcome, thus warranting differing therapeutic modalities/regimens. Recent advances in molecular and cytogenetic techniques have identified a number of additional novel entities, including round cell sarcomas harboring CIC-DUX4 and BCOR-CCNB3 fusions, respectively. These novel findings have not only enhanced our understanding of the pathogenesis of round cell tumors, but also allowed us to reclassify some entities with potential therapeutic and prognostic significance. This article provides an overview focusing on recent molecular genetic advances in primary, nonhematologic round cell tumors of bone.

Ewing sarcoma

Classification of small round cell tumors of bone is often challenging due to overlapping clinicopathologic features. The purpose of this article is to review the clinical, radiological, histologic, and molecular features of Ewing sarcoma and to provide a discussion of the differential diagnosis of small round cell tumors of bone.

Usefulness of a monoclonal ERG/FLI1 antibody for immunohistochemical discrimination of Ewing family tumors

Ewing family tumors (EFTs) and prostate carcinomas are characterized by rearrangement of ETS genes, most commonly FLI1 (EFTs) and ERG (prostate carcinomas). Previously, we characterized an antibody against ERG (EPR3864) for detecting ERG-rearranged prostate carcinoma. Because EPR3864 also cross-reacts with FLI1, we evaluated the usefulness of EPR3864 for discriminating EFTs from other small round blue cell tumors (SRBCTs) with immunohistochemistry. Of 57 evaluable EFTs, 47 (82%) demonstrated at least moderate, diffuse, nuclear ERG/FLI1 staining (including 89% and 100% of cases with confirmed EWSR1:FLI1 and EWSR1:ERG fusions, respectively), of which 1, 3, and 43 showed negative, cytoplasmic, or membranous CD99 staining, respectively. Among other SRBCTs (61 cases, 7 types), at least moderate, diffuse, nuclear EPR3864 staining was seen in all precursor B-lymphoblastic lymphomas/leukemias and subsets of Burkitt lymphomas (10%) and synovial sarcomas (45%). In summary, EPR3864 may be useful in detecting EWSR1:FLI1 and EWSR1:ERG rearranged EFTs in addition to prostate carcinomas.

Small Round Cell Tumors of Bone

Diagnosing small round cell tumors (SCRTs) can be a difficult task for pathologists due to overlapping clinicopathologic features. This review highlights the clinical, radiographic, histologic, immunohistochemical, and genetic features of the most common SRCTs involving bone with an emphasis on differential diagnosis. SRCTs are a heterogeneous group of neoplasms characterized by poorly differentiated cells with small, blue, round nuclei and scant cytoplasm. They can occur as primary tumors in bone or soft tissue.

Anaplastic large cell lymphoma: another entity in the differential diagnosis of small round blue cell tumors

We saw in consultation a biopsy specimen from a 6-year old girl with anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL). The tumor arose in soft tissue of the neck, and diagnostic tissue was obtained by core needle biopsy. Histologically, the neoplasm was cellular without pattern. Immunohistochemical workup with a large panel of antibodies at another institution showed immunoreactivity for NB84 and neuron specific enolase (dim). Antibodies specific for CD3, CD20, and CD45/LCA were negative; CD30 or ALK were not assessed. Electron microscopy showed cytoplasmic structures thought to be neurosecretory granules. The neoplasm was interpreted initially as a neuroblastoma. At the time of our review, we considered the possibility of ALCL. Immunohistochemical analysis for CD30 showed bright, uniform expression and ALK was positive in a nuclear and cytoplasmic pattern, confirming the diagnosis of ALK+ ALCL. The purpose of this review is to discuss ALK+ ALCL and many of the other entities included under the rubric of small round blue cell tumor, with a focus on tumors that occur in children.