NKX3.1 immunoreactivity is not identified in mesenchymal chondrosarcoma: a 25-case cohort study

NKX3.1 Expression in Non-Prostatic Tumors and Characterizing its Expression in Esophageal/Gastroesophageal Adenocarcinoma

The NKX3.1 immunohistochemical stain is widely recognized as a highly sensitive and specific marker for prostate adenocarcinoma. Nevertheless, its expression has been documented in various nonprostatic tissues and malignancies. This review aims to provide an overview of NKX3.1 expression in diverse tumor types, with a specific focus on its aberrant expression in esophageal/gastroesophageal adenocarcinoma (E/GE-ADC). In our investigation, we explored the expression of NKX3.1 in a series of E/GE-ADC to shed light on its prevalence in this tumor category. A total of 50 samples, comprising primary and metastatic E/GE-ADC specimens from 34 patients, were subjected to immunohistochemical analysis. Stained sections were scored based on the intensity and distribution-categorized as negative, weak, moderate, or strong in either a focal or diffuse pattern. Strong staining corresponds to the intensity observed in normal prostate controls, while focal and diffuse staining denote <50% and ≥50% of tumor nuclei staining positive, respectively. Our semiquantitative scoring revealed that 6 (12%) of the primary and metastatic E/GE-ADC specimens exhibited variable positivity for NKX3.1. This finding suggests that E/GE-ADC can sporadically stain positive for NKX3.1, introducing potential challenges in definitively determining the primary site of origin in certain clinical scenarios. Along with a literature review of NKX3.1 expression in other tumor types, our study provides additional important information about the extent to which this immunostain can be seen in E/GE-ADCs, which, to our knowledge, has not been reported.

Mesenchymal Chondrosarcoma from Diagnosis to Clinical Trials

Mesenchymal chondrosarcoma (MCS) is a rare subtype of chondrosarcoma with a poor prognosis. Although these tumors are sensitive to radiotherapy/chemotherapy, the standard treatment for localized MCS is only surgical resection, and there are no established treatment guidelines for patients with advanced and metastatic MCS. Due to the low incidence of MCS, the pathology of these tumors is still unknown, and other therapeutic options are lacking. Some studies show the potential role of the PDGF/PPI3K/AKT, PKC/RAF/MEK/ERK, and pRB pathways, and BCL2 overexpression in the pathogenesis of MCS. These findings provide an opportunity to use protein kinases and BCL2 inhibitors as potential therapy in MCS. In this review, we summarize the current knowledge about MCS diagnosis and treatment options. We show the immunological and molecular biomarkers used in the diagnosis of MCS. In addition, we discuss the known prognostic and predictive factors in MCS. Finally, we present the novel trends, including targeted therapies and ongoing clinical trials using protein kinase inhibitors and the death receptor 5 (DR5) agonist, which may be the focus of future MCS treatment studies.

NKX3.1 immunohistochemistry and methylome profiling in mesenchymal chondrosarcoma: additional diagnostic value for a well-defined disease?

Mesenchymal chondrosarcoma (MCS) is a rare and highly aggressive tumour of soft tissue and bone that is defined by an underlying and highly specific fusion transcript involving HEY1 and NCOA2. Histologically, the tumours show a biphasic appearance consisting of an undifferentiated blue and round cell component as well as islands of highly differentiated cartilage. Particularly in core needle biopsies, the chondromatous component can be missed and the non-specific morphology and immunophenotype of the round cell component can cause diagnostic challenges. We applied NKX3.1 immunohistochemistry which was recently reported as a highly specific marker as well as methylome and copy number profiling to a set of 45 well characterised MCS cases to evaluate their potential diagnostic value. Methylome profiling revealed a highly distinct cluster for MCS. Notably, the findings were reproducible also when analysing the round cell and cartilaginous component separately. Furthermore, four outliers were identified by methylome profiling for which the diagnosis had to be revised. NKX3.1 immunohistochemistry showed positivity in 36% of tumours, the majority of which was rather focal and weak. Taken together, NKX3.1 expression showed a low sensitivity but a high specificity in our analysis. Methylome profiling on the other hand represents a sensitive, specific and reliable tool to support the diagnosis of MCS, particularly if only the round cell component is obtained in a biopsy and the diagnosis is not suspected. Furthermore, it can aid in confirming the diagnosis in case RNA sequencing for the HEY1::NCOA2 fusion transcript is not available.

[Fusion-related round and spindle cell sarcomas of the bone (beyond Ewing)]

Round cell sarcomas represent a diagnostic challenge for pathologists due to the poorly differentiated pattern of these high-grade tumors. Their diagnosis often requires large immunohistochemical panels and the use of molecular pathology. These tumors are largely dominated by Ewing sarcomas, but new families are now well characterized, including in decreasing frequency order in bone, BCOR-altered sarcomas, NFATc2-rearranged sarcomas, mesenchymal chondrosarcomas and more rarely CIC-rearranged sarcomas and myoepithelial tumors. This progress report presents microscopic, immunohistochemical and molecular features of these tumors previously named by the inappropriate term "Ewing-like" sarcomas, in order to enable any pathologist to perceive the morphological features of these sarcomas, to select the immunohistochemical panel that will lead to the diagnosis and to better guide the molecular approach needed to establish the final diagnosis.

Advances in the classification of round cell sarcomas

Round cell sarcomas represent a diagnostic challenge for pathologists, owing to the poorly differentiated features of these high-grade tumours. The diagnosis of round cell sarcoma requires large immunohistochemical panels and molecular testing in many cases. This spectrum of malignancies is largely dominated by Ewing sarcomas (ESs), which represent the most common family of these tumours. Nonetheless, new families have been delineated in the past few years, with the addition of two additional families in the 2020 World Health Organization classification of bone and soft tissue tumours, namely sarcomas with CIC rearrangements and sarcomas with BCOR alterations. EWSR1, one of the genes involved in the driver fusion of ESs, is also implicated in the translocation of many other tumours with heterogeneous lineages and variable levels of aggressiveness. Round cell sarcomas associated with fusions inwhichEWSR1is partnered with genes encoding transcription factors distinct from those of the 'Ewing family' represent a heterogeneous group of rare tumours that require further study to determine whether their fusions may or not define a specific subgroup. They include mainly sarcomas with NFATc2 rearrangements and sarcomas with PATZ1 rearrangements. At this point, PATZ1 fusions seem to be associated with tumours of high clinical and morphological heterogeneity. Molecular studies have also helped in the identification of more consistent biomarkers that give tremendous help to pathologists in triaging, if not diagnosing, these tumours in practice. This review compiles the latest accumulated evidence regarding round cell sarcomas, and discusses the areas that are still under investigation.

Malignant Cartilage-Forming Tumors

Chondrosarcomas are heterogeneous matrix-producing cartilaginous neoplasms with variable clinical behavior. Subtypes include conventional (75%), dedifferentiated (10%), clear cell (2%), mesenchymal (2%), and periosteal chondrosarcoma (<1%). Tumor location and primary vs secondary also play a role. In conventional chondrosarcoma, histologic grading (I, II, and III) remains the gold standard for predicting recurrence and metastases. Due to the locally aggressive but overall nonmetastatic behavior, grade I chondrosarcomas (primary and secondary) of long and short tubular bones have been reclassified as atypical cartilaginous tumor. In this review, the pathologic features of malignant cartilage tumors are discussed with updates on recent genetic findings.

From the ashes of "Ewing-like" sarcoma: A contemporary update of the classification, immunohistochemistry, and molecular genetics of round cell sarcomas

Round cell sarcomas include a diverse group of bone and soft tissue tumors, which comprise well-defined entities as well as several nascent categories presented in the 2020 World Health Organization classification. The morphologic overlap yet disparate nosology, prognostic implications, and management strategies places a high value on ancillary testing, including a strategic immunohistochemical approach and directed confirmation by cytogenetic and molecular genetic methods. We review the diagnostic categories that have emerged from the former wastebasket "undifferentiated round cell sarcoma" ("Ewing-like" sarcomas), with an emphasis on algorithmic exclusion of nonsarcomatous entities, diagnostic stratification of well-defined entities (Ewing sarcoma, rhabdomyosarcomas, poorly differentiated synovial sarcoma), and a discussion of the new categories with novel genetic alterations (CIC-rearranged sarcomas, sarcomas with BCOR genetic alterations, and round cell sarcomas with EWSR1-non-ETS fusions).

Diagnostic Immunohistochemistry of Soft Tissue and Bone Tumors: An Update on Biomarkers That Correlate with Molecular Alterations

The diagnosis of benign and malignant soft tissue and bone neoplasms is a challenging area of surgical pathology, due to the large number, rarity, and histologic diversity of tumor types. In recent years, diagnosis and classification has been aided substantially by our growing understanding of recurrent molecular alterations in these neoplasms. Concurrently, the role of diagnostic immunohistochemistry has also expanded, with the development of numerous biomarkers based on underlying molecular events. Such biomarkers allow us to infer the presence of these events and can therefore substitute for other ancillary molecular genetic techniques (e.g., fluorescence in situ hybridization, polymerase chain reaction, and next-generation sequencing). In this review, we discuss a range of biomarkers currently available for these neoplasms, highlighting the accuracy, staining characteristics, and interpretation pitfalls of each antibody. These include immunohistochemical antibodies that represent reliable surrogates for the detection of gene fusions (e.g., STAT6, CAMTA1, FOSB, DDIT3) and more recently described breakpoint-specific antibodies (e.g., SS18-SSX, PAX3/7-FOXO1). Additionally, discussed are markers that correlate with the presence of gene amplifications (e.g., MDM2, CDK4), deletions (e.g., SMARCB1, SMARCA4), single nucleotide variants (e.g., G34W, K36M), aberrant methylation (H3K27me3), and increased expression as discovered through gene expression profiling (e.g., MUC4, DOG1, ETV4, NKX2.2, NKX3.1).