At the intersection of primary pulmonary myxoid sarcoma and pulmonary angiomatoid fibrous histiocytoma: observations from three new cases

Application of 18F-FDG PET/CT imaging in a primary angiomatoid fibrous histiocytoma of pulmonary bronchus: case report and literature review

Background

Angiomatoid fibrous histiocytoma (AFH) is a clinically rare, low-grade malignant soft tissue tumor that occasionally metastasizes. It accounts for 0.3% of all soft tissue tumors and most frequently occurs in the extremities, followed by the trunk, and the head and neck. Primary angiomatoid fibrous histiocytoma (PAFH) of the pulmonary bronchus is rare. In this paper, the clinical and imaging data of a case of PAFH of the pulmonary bronchus are reported, and the literature is reviewed.

Case description

A 57-year-old female patient presented with a six-month history of cough without apparent cause, characterized by paroxysmal dry cough, chest tightness, and shortness of breath, which worsened with activity. She did not experience fever, chills, chest pain, hemoptysis, or night sweats. Laboratory tests revealed an elevated C-reactive protein and ferritin levels, while tumor markers such as AFP, CEA, CA199, CA125, CA50, and T-SPOT were negative. A chest CT scan showed bronchial obstruction, atelectasis, and a soft tissue density in the right middle lobe of the lung. The enhanced scan demonstrated uneven enhancement of endobronchial nodules. An 18F-FDG PET/CT scan revealed a nodular soft tissue density shadow in the right lung bronchus with uneven density, clear boundaries, and increased 18F-FDG uptake, with a maximum standard uptake value (SUVmax) of 11.2. Bronchoscopy revealed a nodular or polypoid mass that was yellow and tough. Based on imaging findings, the preoperative diagnosis favored lung cancer. However, the postoperative pathological diagnosis confirmed primary angiomatoid fibrous histiocytoma (PAFH) of the pulmonary bronchus.

Conclusion

The incidence of primary angiomatoid fibrous histiocytoma (PAFH) is very low, and its clinical manifestations and imaging findings lack specificity, with the final diagnosis relying on pathology. PET/CT imaging has a certain value in the diagnosis of PAFH and holds significant application value in preoperative staging, postoperative efficacy evaluation, and follow-up monitoring. In conclusion, this case report further expands the spectrum of lung and bronchial tumors.

Sarcoma of the Lung and Mediastinum

Primary sarcoma of the lung and mediastinum is rare. The diagnosis requires careful exclusion of sarcomatoid carcinoma, sarcomatoid mesothelioma, and metastases from extra-thoracic sites. This review summarizes the key morphologic, immunohistochemical, and molecular characteristics of sarcomas that are encountered in the lung and mediastinum. The tumor types discussed are synovial sarcoma, well-differentiated/dedifferentiated liposarcoma, myxoid pleomorphic liposarcoma, intimal sarcoma of the pulmonary artery, inflammatory myofibroblastic tumor, epithelioid hemangioendothelioma, primary pulmonary myxoid sarcoma, malignant peripheral nerve sheath tumor, Ewing sarcoma, and CIC-rearranged sarcoma. Relevant differential diagnoses are also addressed.

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.

[Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion]

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion is an extremely rare tumor. Its clinical manifestation is unspecific and only molecular genetic method can proof this diagnosis. This paper describes an unusual clinical presentation of primary pulmonary myxoid sarcoma in a 68-year-old patient with involvement of both lungs.

CT findings of a large primary pulmonary myxoid sarcoma: A case report

Primary pulmonary myxoid sarcoma (PPMS) is an extremely rare malignant mesenchymal tumor of the lung, with only less than 40 cases reported. We described a case of a 64-years-old man with a mass on the medial and lower lobe of the right lung confirmed as a primary pulmonary myxoid sarcoma on biopsy. Diagnosis of this tumor remains challenging because of its nonspecific clinical and imaging characteristics. This study emphasizes CT finding to improve the understanding of PPMS.

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.

Endobronchial Primary Pulmonary Angiomatoid Fibrous Histiocytoma in a Patient with Testicular Germ Cell Tumor: An Evidence Against Somatic Transformation

Primary Pulmonary Angiomatoid Fibrous Histiocytoma is a recently described soft tissue tumor with challenging differential diagnosis both clinically and pathologically due to its rarity in this location. It may also occur as a secondary malignancy and its occurrence either as a somatic malignancy arising in the germ cell tumor or as a secondary malignancy after chemotherapy is questionable. In this report, we present a 29-year-old male patient with a mass in the lower lobe of the left lung, who underwent orchiectomy and received adjuvant chemotherapy due to a mixed germ cell tumor 8 years ago. Morphology, immunophenotype, and molecular findings were consistent with the diagnosis of primary pulmonary angiomatoid fibrous histiocytoma. Fluorescent in situ hybridization was unable to demonstrate the presence of 12p amplification or isochromosome 12p, which is known as the key event in the development of testicular germ cell neoplasia even present in somatic malignancies arising in germ cell tumors. Our results support that angiomatoid fibrous histiocytoma arising as a secondary malignancy does not represent the somatic transformation of germ cell tumors.

Unusual lung tumors-from morphology to genetics

Most pathologists are well versed in the diagnosis of lung cancer, given the common nature of the disease. Occasionally more unusual neoplasms are encountered in lung biopsies and resections, which may be difficult to distinguish from "run of the mill" lung cancer cases based on overlapping morphologic and immunophenotypic features. The accurate diagnosis of these rare entities is quite challenging and requires careful morphological examination paired with judicious use of ancillary immunohistochemical and genetic studies. Herein, the clinicopathological and genetic features of five unusual lung tumors will be reviewed, including thoracic SMARCA4-deficient undifferentiated tumor, NUT carcinoma, sclerosing pneumocytoma, primary pulmonary myxoid sarcoma/angiomatoid fibrous histiocytoma, and bronchiolar adenoma/ ciliated muconodular papillary tumor. Since recognition of these entities by pathologists is of increasing importance to guide prognosis and therapy, emphasis will be placed on practical tips to reach these rare diagnoses with confidence.

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.

[Primary pulmonary myxoid sarcoma associated with translocation EWSR1-CREB1 and locorregional micrometastases]

Primary myxoid pulmonary sarcoma is a rare entity with an endobronchial growth. Although it should be included in the differential diagnosis of other sarcomas, its prognosis is usually favorable. We present the case of a 51-year-old patient with a mesenchymal tumor in the right lung, diagnosed as a primary pulmonary myxoid sarcoma, positive for EMA, vimentine and with a Ki-67 less than 5%; FISH revealed a EWSR1-CREB1 translocation.

Primary Pulmonary Myxoid Sarcoma and Myxoid Angiomatoid Fibrous Histiocytoma: A Unifying Continuum With Shared and Distinct Features

Primary pulmonary myxoid sarcoma (PPMS) is a recently reported, exceedingly rare low-grade lung neoplasm characterized by reticular/lace-like growth of spindle to epithelioid cells embedded in an abundant myxoid matrix. Morphologically, it overlaps with a myxoid variant of angiomatoid fibrous histiocytoma (AFH) of the soft tissue. Genetically, they were both reported to harbor EWSR1-CREB1 fusion, while EWSR1-ATF1 has only been reported in AFH thus far. We report a case of primary pulmonary low-grade myxoid spindle cell tumor with morphologic and immunohistochemical features of PPMS but with an EWSR1-ATF1 fusion gene. In addition, we also encountered a case of endobronchial AFH with EWSR1-CREB1 translocation but also focal morphologic features of PPMS. These findings provide new evidence supporting the concept that PPMS and a myxoid variant of AFH represent a continuum with overlapping histologic, immunohistochemical, and genetic features.

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: a case report and review of the literature

BACKGROUND

Primary pulmonary myxoid sarcoma (PPMS) is an extremely rare lung sarcoma that is characterized in most cases by recurrent balanced chromosomal translocation t(2;22)(q33;q12) leading to the oncogenic fusion gene EWSR1-CREB1.

CASE PRESENTATION

We report a case of PPMS with molecular confirmation using fluorescence in situ hybridization (FISH) and DNA sequencing in a 45-year-old female patient. Computer tomography (CT) scanning revealed a peripheral circumscribed solid mass of 2.1 × 2 cm in the right lung superior lobe. Histologically, the tumor cells ranged from stellate, polygonal to chondrocyte-like or physaliferous-like, forming reticular network of delicate lace-like cellular strands and cords in abundant myxoid stroma. The tumor cell immunophenotype was positive for vimentin, EMA and negative for CK-pan, TTF-1, CAM5.2, S-100, calponin, SMA, desmin, ALK, CD31 and CD34. Molecular analysis demonstrated EWSR1-CREB1 gene fusion in this tumor. During 38 months of follow-up, the patient was alive with no clinical or radiological evidence of recurrence or metastasis.

CONCLUSION

PPMS is a rare low-grade sarcoma with distinct histological and genetic features. We add another case to the literature of this rare tumor and report for the first time occurrence of chondrocyte-like and physaliferous-like tumor cells in this tumor, thus enriching its morphologic and cytologic spectrum.

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

Primary pulmonary mesenchymal tumors are rare, yet they compromise a variety of entities. A novel low-grade malignant neoplasm coined primary pulmonary myxoid sarcoma (PPMS) has been introduced in the WHO classification of lung tumors. Molecular analysis in PPMS revealed recurrent gene fusions between EWSR1 and CREB1, a member of the cAMP response element binding protein (CREB) family. However, only 23 PPMS have been reported in the literature reflecting their exceedingly low incidence. Here, we describe the case of a 41-year-old female patient with a lung tumor obstructing the right main bronchus. Histologically, the tumor was composed of spindle-shaped and epithelioid cells exhibiting a reticular growth pattern within a prominent myxoid matrix. Solid areas were also observed. Molecular analysis by next-generation sequencing identified a fusion transcript with an unusual gene fusion involving exon 7 of EWSR1 and exon 5 of CREB1. Together, the diagnosis PPMS was established.

EWSR1 Fusions With CREB Family Transcription Factors Define a Novel Myxoid Mesenchymal Tumor With Predilection for Intracranial Location

Recurrent gene fusions involving EWSR1 with members of the cAMP response element binding protein (CREB) family (ATF1 and CREB1) have been reported in a diverse group of tumors including angiomatoid fibrous histiocytoma (AFH), soft tissue and gastrointestinal clear cell sarcoma, primary pulmonary myxoid sarcoma, and hyalinizing clear cell carcinoma of salivary gland. We have recently encountered a group of 5 myxoid mesenchymal tumors positive for EWSR1 fusions with one of the CREB family member (ATF1, CREB1, and CREM), with histologic features distinct from any of the previously described pathologic entities. Tumors occurred in children or young adults (12 to 23 y; mean, 18 y), with equal sex distribution. All except 1 were intracranial (intra-axial, 2; meningeal, 2), whereas 1 was perirectal. Histologically, the tumors were well circumscribed, often lobulated, composed of uniform ovoid to round cells, and arranged in cord-like or reticular structures in a myxoid background. All except 1 displayed unique sunburst amianthoid fibers. Immunohistochemically, tumors were positive for epithelial membrane antigen (5/5; 4 focal, 1 diffuse) and desmin (3/5). A novel EWSR1-CREM fusion was identified by RNA sequencing in the perirectal tumor, which was further confirmed by fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR). A second case with similar EWSR1-CREM fusion was identified by RT-PCR and FISH in a meningeal tumor. The remaining cases studied by FISH showed the presence of EWSR1-CREB1 fusion in 2 cases and EWSR1-ATF1 in 1. In conclusion, we report a distinct group of myxoid mesenchymal neoplasms occurring in children or young adults with a predilection for intracranial locations. Although the immunoprofile [epithelial membrane antigen (EMA), desmin] and the fusion type raise the possibility of a myxoid AFH, none of the typical histologic findings of AFH were present, suggesting a novel entity.

Primary Pulmonary Myxoid Sarcoma: A Newly Described Entity-Report of a Case and Review of the Literature

Primary pulmonary myxoid sarcoma (PPMS) is a recently described, exceedingly rare low-grade lung sarcoma that tends to present in young females as an endobronchial mass and shows evidence of an EWSR1- CREB1 fusion. Herein, we present a case of PPMS with fluorescence in situ hybridization (FISH) analysis for EWSR1 and CREB1 rearrangements. An 80-year-old woman presented with an endobronchial, multinodular tumor exhibiting spindle, ovoid and epithelioid cells arranged in reticular/lattice-like and alveolar-like patterns in a myxoid background. The tumor showed focal epithelial membrane antigen immunoreactivity as well as an Alcian blue-positive stroma that was sensitive to digestion with hyaluronidase. EWSR1 and CREB1 rearrangements were detected by break-apart FISH probes. The patient showed persistence of disease 36 months after diagnosis and was discharged to hospice care. We contribute with a report of an additional case of this very unusual entity and perform a brief review of the literature published so far on the subject.

Intracranial myxoid mesenchymal tumors with EWSR1-CREB family gene fusions: myxoid variant of angiomatoid fibrous histiocytoma or novel entity?

Intracranial myxoid mesenchymal tumor harboring EWSR1 fusions with CREB family of genes was recently described, and it resembles the myxoid variant of angiomatoid fibrous histiocytoma. We present three pediatric patients with intracranial EWSR1-rearranged myxoid mesenchymal neoplasm and provide a molecular genetic characterization of these tumors. Clinical histories and imaging results were reviewed. Histology, immunohistochemistry, EWSR1, FUS, NR4A3 fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS) were performed. A 12-year-old male (case 1), 14-year-old female (case 2), and 18-year-old male (case 3), presented with headaches, emesis, and seizures, respectively. The magnetic resonance images demonstrated tumors abutting the dura (cases 1 and 3) and in the third ventricle (case 2). All tumors were vascular, with solid sheets of monomorphic oval cells in a prominent myxoid/microcystic matrix. A thin fibrous pseudocapsule was present in all lesions, but definitive lymphocytic cuffing was absent. Morphologically, they closely resembled myxoid variant of angiomatoid fibrous histiocytoma. Mitoses were rare, and necrosis was absent. All tumors expressed desmin and GLUT1, and focal EMA and CD99. The proliferation index was low. FISH and NGS showed EWSR1-CREB1 fusion (cases 1 and 2), and EWSR1-CREM fusion (case 3). There were no FUS (16p11.2) or NR4A3 (9q22.33) rearrangements in case 3. Gains of 5q (including KCNIP1) and 11q (including CCND1) were present in cases 1 and 2. There were no common pathogenic genomic changes other than EWSR1 rearrangements across cases. CNS myxoid mesenchymal neoplasms with histological and immunophenotypic similarities to myxoid variant of AFH are rare, diagnostically challenging, and harbor EWSR1-CREB1 and also a novel EWSR1-CREM fusion not yet described in AFH. Therefore, it is uncertain if these tumors represent variants of AFH or a new entity. The copy number and mutational changes presented here provide support for future studies to further clarify this issue.