Primary pulmonary myxoid sarcoma with an unusual gene fusion between exon 7 of EWSR1 and exon 5 of CREB1

Primary pulmonary myxoid sarcoma in the interlobar fissure of the left lung lobe: a case report

BACKGROUND

Primary pulmonary myxoid sarcoma (PPMS) is a rare, low-grade malignant tumor, constituting approximately 0.2% of all lung tumors. Despite its rarity, PPMS possesses distinctive histological features and molecular alterations, notably the presence of EWSR1-CREB1 gene fusion. However, its precise tissue origin remains elusive, posing challenges in clinical diagnosis.

CASE DEMONSTRATION

A 20-year-old male patient underwent a routine physical examination 6 months prior, revealing a pulmonary mass. Following surgical excision, microscopic evaluation unveiled predominantly short spindle-shaped tumor cells organized in a fascicular, beam-like, or reticular pattern. The stromal matrix exhibited abundant mucin, accompanied by lymphocytic and plasma cell infiltration, with Russell bodies evident in focal areas. Immunophenotypic profiling revealed positive expression of vimentin and epithelial membrane antigen in tumor cells, whereas smooth muscle actin and S-100, among others, were negative. Ki-67 proliferation index was approximately 5%. Subsequent second-generation sequencing identified the characteristic EWSR1-CREB1 gene fusion. The definitive pathological diagnosis established PPMS. The patient underwent no adjuvant chemotherapy or radiotherapy and remained recurrence-free during a 30-month follow-up period.

CONCLUSIONS

We report a rare case of PPMS located within the left lung lobe interlobar fissure, featuring Russell body formation within the tumor stroma, a novel finding in PPMS. Furthermore, the histomorphological characteristics of this case highlight the diagnostic challenge it poses, as it may mimic inflammatory myofibroblastic tumor, extraskeletal myxoid chondrosarcoma, or hemangiopericytoma-like fibrous histiocytoma. Therefore, accurate diagnosis necessitates an integrated approach involving morphological, immunohistochemical, and molecular analyses.

Primary Pulmonary Myxoid Sarcoma and Thoracic Angiomatoid Fibrous Histiocytoma: Two Sides of the Same Coin?

Primary pulmonary myxoid sarcoma (PPMS) and thoracic angiomatoid fibrous histiocytoma (AFH) are rare neoplasms with EWSR1 fusions and overlapping morphology. Both tumor types often show epithelial membrane antigen expression, but AFH characteristically co-expresses desmin. We encountered a case of PPMS with the unexpected finding of patchy, strong anaplastic lymphoma kinase (ALK) (previously reported in AFH) and synaptophysin expression. We evaluated a cohort of PPMS and thoracic AFH with systematic morphologic comparison and surveyed for aberrant expression of ALK and synaptophysin. Medical records and slides were reviewed for 16 molecularly confirmed cases of PPMS (n=5) and thoracic AFH (n=11). Each case was scored for morphologic characteristics typical of PPMS and/or AFH. ALK, synaptophysin, chromogranin, desmin, and epithelial membrane antigen immunostains were performed on cases with available tissue. AFH and PPMS cases showed similar age at presentation and long-term tumor behavior. Almost all cases of PPMS and AFH had a fibrous pseudocapsule and lymphoid rim. All PPMS had myxoid stroma and reticular growth pattern, but these features were also present in a subset of AFH. Synaptophysin expression was present in 6 of 11 AFH and 1 of 5 PPMS; all tested cases were negative for chromogranin (n=15). One case of AFH and 1 case of PPMS showed focally strong coexpression of synaptophysin and ALK. AFH and PPMS show considerable clinicopathologic overlap. When supportive, the immunohistochemical findings described may aid in diagnosis before molecular confirmation. PPMS and AFH may be morphologic variants of the same clinicopathologic entity, which can show more immunophenotypic variability than previously reported.

Primary pulmonary myxoid sarcoma with EWSR1::CREB1 fusion: a literature review

PURPOSE

This review primarily aims to review the epidemiology, clinical characteristics, imaging, pathology, immunohistochemistry, diagnosis, differential diagnosis, treatment, and prognosis of Primary pulmonary myxoid sarcoma (PPMS) with EWS RNA binding protein 1::cAMP response element binding protein 1 (EWSR1::CREB1) fusion. It provides reference for the diagnosis and treatment of this disease.

METHODS

Retrospectively collected the literature about PPMS with EWSR1::CREB1 fusion, its clinical, radiology, histology, molecular characteristics and current treatment strategies were collated and analyzed. This review provides a detailed differential diagnosis of the disease.

RESULTS

PPMS is an exceptionally rare, low-grade malignant tumor of the lung. This tumor commonly infiltrates lung tissue and develops within bronchial passages. It is identified by a genetic rearrangement involving the EWSR1 gene and a distinct chromosomal translocation t(2; 22)(q33; q12). Variants include EWSR1::CREB1 fusion and EWS RNA binding protein 1::activating transcription factors (EWSR1::ATF1) fusion. PPMS with EWSR1::CREB1 fusion is more prevalent among middle-aged individuals and affects both sexes almost equally. Clinical symptoms are relatively non-specific, primarily including cough, hemoptysis, and weight loss. Most patients undergo surgery and experience a favorable prognosis. Further research is required to validate the effectiveness of alternative treatments for PPMS with EWSR1::CREB1 fusion.

CONCLUSION

EWSR1 rearrangement and EWSR1::CREB1 fusion are crucial genetic features of PPMS and serve as important diagnostic markers. Immunohistochemically, PPMS tests positive for EMA. In terms of treatment, surgery has been the primary approach in recent years. Therefore, the efficacy of other treatments still requires further investigation.

Comprehensive genomic profiling of EWSR1/FUS::CREB translocation-associated tumors uncovers prognostically significant recurrent genetic alterations and methylation-transcriptional correlates

To elucidate the mechanisms underlying the divergent clinicopathologic spectrum of EWSR1/FUS::CREB translocation-associated tumors, we performed a comprehensive genomic analysis of fusion transcript variants, recurrent genetic alterations (mutations, copy number alterations), gene expression, and methylation profiles across a large cohort of tumor types. The distribution of the EWSR1/FUS fusion partners-ATF1, CREB1, and CREM-and exon involvement was significantly different across different tumor types. Our targeted sequencing showed that secondary genetic events are associated with tumor type rather than fusion type. Of the 39 cases that underwent targeted NGS testing, 18 (46%) had secondary OncoKB mutations or copy number alterations (29 secondary genetic events in total), of which 15 (52%) were recurrent. Secondary recurrent, but mutually exclusive, TERT promoter and CDKN2A mutations were identified only in clear cell sarcoma (CCS) and associated with worse overall survival. CDKN2A/B homozygous deletions were recurrent in angiomatoid fibrous histiocytoma (AFH) and restricted to metastatic cases. mRNA upregulation of MITF, CDH19, PARVB, and PFKP was found in CCS, compared to AFH, and correlated with a hypomethylated profile. In contrast, S100A4 and XAF1 were differentially upregulated and hypomethylated in AFH but not CCS. Unsupervised clustering of methylation profiles revealed that CREB family translocation-associated tumors form neighboring but tight, distinct clusters. A sarcoma methylation classifier was able to accurately match 100% of CCS cases to the correct methylation class; however, it was suboptimal when applied to other histologies. In conclusion, our comprehensive genomic profiling of EWSR1/FUS::CREB translocation-associated tumors uncovered mostly histotype, rather than fusion-type associated correlations in transcript variants, prognostically significant secondary genetic alterations, and gene expression and methylation patterns.

Distinct clinicopathological features of pulmonary primary angiomatoid fibrous histiocytoma: A report of four new cases and review of the literature

BACKGROUND

The aim of this study was to highlight the clinicopathological features of pulmonary primary angiomatoid fibrous histiocytoma (PPAFH) to assist with a differential diagnosis.

METHODS

There were 10 previous reports in the literature and four new PPAFH cases reviewed in this study. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH) and DNA and RNA-based next-generation sequencing (NGS) was performed in the four new cases reported here.

RESULTS

In the four new PPAFH cases, the ages of occurrence were in patients age from 33 to 55 years and tumor sizes were from 1.5 to 8 cm. Three of four (75.0%) tumors were located in the endobronchus. The most common morphological changes included delineated fibrous capsule (100%, 4/4), lymphoplasmacytic cuff (100%, 4/4), and dense or richly lymphoplasmatic infiltration (100%, 4/4). IHC analysis revealed that the tumor cells of four cases expressed vimentin and TLE1, ALK and CD163 or CD68 was positive in three cases, epithelial membrane antigen (EMA), desmin was positive in two cases, and SMA focal positive expression was observed in two cases. EWSR1 gene rearrangement was positive in all PPAFH cases (100%, 4/4) by FISH detections and four cases were confirmed as EWSR1-CREB1 fusion variant by DNA and RNA based NGS. No regional lymph nodes and distal metastasis, recurrences and death of disease after surgical excision were recorded in all four cases.

CONCLUSIONS

PPAFH is a very unusual pulmonary primary mesenchymal tumor and the clinicopathological features are like other unusual sites counterparts, but with a smaller tumor size, related with large airway, with a tendency to exhibit benign biological behavior, with EWSR1 gene rearrangement and higher frequency of EWSR1-CREB1 gene fusion.

KEY POINTS

Significant findings in the study: In comparison with "classic somatic" and nonpulmonary visceral angiomatoid fibrous histiocytoma, pulmonary primary angiomatoid fibrous histiocytoma display distinct clinicopathological features and prognosis. What this study adds The study provided the pathological differential diagnostic criteria and clinico-pathological features for pulmonary primary angiomatoid fibrous histiocytoma.