Brachyury expression in intracranial SMARCB1-deficient tumors: important points for distinguishing poorly differentiated chordoma from atypical teratoid/rhabdoid tumor

Poorly differentiated extra-axial extraskeletal chordoma diagnosed by methylation profiling: case report and analysis of brachyury expression in SWI/SNF-deficient tumors

Chordoma is a rare malignant tumor with notochordal differentiation, usually affecting the axial skeleton of young patients. We report a case of a high-grade epithelioid tumor involving the synovium and soft tissues of the knee in a 74-year-old male patient. The preliminary biopsy was inconclusive, but a diagnosis of metastatic clear-cell carcinoma of unknown origin was suggested. However, imaging studies did not reveal any primary lesions. The resection specimen consisted of nests and sheets of oval to polygonal cells with discernible cell borders, clear or lightly amphophilic cytoplasm, and round to oval nuclei with occasional well-visible eosinophilic nucleoli. Rare atypical mitoses, necrotic areas, and bizarre nuclei were noted. The biopsy and resection specimens underwent a wide molecular genetic analysis which included methylation profiling. The DKFZ sarcoma classifier assigned the methylation class chordoma (dedifferentiated) with a calibrated score of 0.96, and additionally, a loss of SMARCB1 locus was noted in the copy number variation plot. To verify these findings, T-brachyury and SMARCB1 immunostaining was performed afterward, showing diffuse nuclear positivity and complete loss in the tumor cells, respectively. To assess the prevalence of T-brachyury immunopositivity among SWI/SNF-deficient tumors and to evaluate its specificity for poorly differentiated chordoma, we analyzed a series of 23 SMARCB1- or SMARCA4-deficient tumors, all of which were negative. After incorporating all the available data, including the absence of any morphological features of conventional chordoma, the case was diagnosed as poorly differentiated chordoma. As illustrated herein, the utilization of methylation profiling in the diagnostic process of some carefully selected unclassifiable soft tissue neoplasms may lead to an increased detection rate of such extremely rare soft tissue tumors and enable their better characterization.

A Rare Case of Adult Poorly Differentiated Chordoma of the Skull Base With Rapid Progression and Systemic Metastasis: A Review of the Literature

Chordoma is a rare tumor that arises from chordal tissue during fetal life. Recently, the concept of poorly differentiated chordoma, a subtype of chordoma characterized by loss of SMARCB1/INI1 with a poorer prognosis than conventional chordomas, was established. It predominantly occurs in children and is rare in adults. Here, we report a rare adult case of poorly differentiated chordoma of the skull base with a unique course that rapidly systemically metastasized and had the shortest survival time of any adult chordoma reported to date. The patient was a 32-year-old male with a chief complaint of diplopia. MRI showed a widespread neoplastic lesion with the clivus as the main locus. Endoscopic extended transsphenoidal tumor resection was performed. Pathological findings showed that the tumor was malignant, and immunohistochemistry revealed a Ki-67 labeling index of 80%, diffusely positive brachyury, and loss of INI1 expression. The final diagnosis was poorly differentiated chordoma. Postoperatively, the residual tumor in the right cavernous sinus showed rapid growth. The patient was promptly treated with gamma knife three fractions. The residual tumor regressed, but the tumor developed systemic metastasis in a short period, and the patient died seven months after diagnosis. This report of a rapidly progressing and fatal adult poorly differentiated chordoma shows the highest Ki-67 labeling index reported to date. Prompt multidisciplinary treatment should be considered when the Ki-67 labeling index is high.

Bibliometric analysis of the global research trends and hotspots in chordoma from 2000 to 2020

INTRODUCTION

Chordoma is formed from embryonic residues or ectopic chordae and locally aggressive or malignant tumors. We visually analyzed the research tendency and hotspot of chordoma.

METHODS

The bibliometric analysis was conducted from the Web of Science Core Collection database over the past two decades. The term and strategies were as follows: "TS = (chordoma) OR TS = (chordoblastoma) OR TS = (chordocarcinoma) OR TS = (chordoepithelioma) OR TS = (chordosarcoma) OR TS = (notochordoma). AND Language: English. AND Reference Type: Article OR Review". A total of 2,118 references were retrieved and used to make a visual analysis by VOSviewer 1.6.15.

RESULTS

The chordoma was on a steady rise and chordoma but remained the focus of scholars and organizations over the last two decades. The Chinese institutions and scholars lacked cooperation with their counterparts in other countries. The citations of documents and co-citation analysis of cited references suggested that M.L. McMaster, B.P. Walcott, P. Bergh, and S. Stacchiotti were leading researchers in this field of chordoma and their papers had been widely accepted and inspired recent researches. Keywords associated with recent chemotherapy, PD-1-related immunotherapy, and SMARCB1/integrase interactor 1 (INI1) in chordoma were a shortage of research and there may be more research ideas in the future by scholars. The research of chordoma will continue to be the hotspot.

CONCLUSIONS

Thus, explaining the molecular mechanism and potential role of transcriptional inhibition and immunologic responses to SMARCB1/INI1-negative poorly differentiated chordoma will be available for preclinical experiments and clinical trials and lead to new therapeutic opportunities for chordoma patients.

Poorly differentiated chordoma showing loss of SMARCB1/INI1: Clinicopathological and radiological spectrum of nine cases, including uncommon features of a relatively under-recognized entity

Poorly differentiated chordoma is a newly recognized entity in the recent World Health Organization (WHO) classification of tumors of soft tissue and bone. Slightly over 60 such cases have been documented. Herein, we present a clinicopathological profile, including radiological features, of nine cases, which occurred in five males and four females, with age varying from 1 to 29 years (median = 43), in the cervical spine (n = 2), skull base (n = 2), clivus (n = 2), thoracic spine (n = 1) lumbar spine (n = 1) and coccyx (n = 1) Average tumor size was 4.8 cm. None of the 6-referral cases was diagnosed as a poorly differentiated chordoma at the referring laboratory. Histopathologically, all cases displayed a cellular tumor comprising polygonal cells (n = 9) displaying moderate to marked nuclear pleomorphism with prominent nucleoli (n = 7), eosinophilic (n = 9) to vacuolated cytoplasm (n = 7), rhabdoid morphology (n = 4), interspersed mitotic figures (n = 5), focal necrosis (n = 6) and inflammatory cells (n = 9). A single tumor displayed areas resembling classic chordoma, transitioning into poorly differentiated areas. There were multinucleate giant cells and physaliphorous cells in two tumors, each, respectively. Immunohistochemically, tumor cells were positive for AE1/AE3 (7/7), EMA (7/7), cytokeratin (CK) MNF116 (1/1), OSCAR (1/1), brachyury (9/9, diffusely), S100P (4/7, mostly focally), and glypican 3(2/4). SMARCB1/INI1 was completely lost in all nine tumors. A single case tested by FISH showed homozygous deletion of the SMARCB1 gene. Therapeutically (n = 7), all patients were treated with surgical resection (invariably incomplete) (n = 5), followed by adjuvant radiation therapy (n = 4) and chemotherapy (n = 4). While a single patient partially responded to treatment and another patient is alive with no evidence of disease after 23 years, three patients died of disease, six, eight, and 11 months post-diagnosis, despite adjuvant treatments. A single patient presented with a metastatic lung nodule, while another developed widespread metastasis. Poorly differentiated chordomas display a spectrum of features, are associated with a lower index of suspicion for a diagnosis, and display aggressive outcomes. Critical analysis of radiological and histopathological features, including necessary immunostains (brachyury and SMARCB1/INI1), is necessary for their timely diagnosis. These tumors show loss of SMARCB1/INI1 immunostaining and homozygous deletion of INI1/SMARCB1 gene.