Reticular angiomatoid “malignant” fibrous histiocytoma—a case report with cytogenetics and molecular genetic 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.

Angiomatoid Fibrous Histiocytoma of the Chest Wall Protruding into the Thoracic Cavity Mimicking Metastasis in a Patient with Breast Cancer

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of intermediate malignancy and uncertain differentiation. To date, only four patients diagnosed with AFH located in the chest wall have been described. Herein, we describe a 44-year-old woman diagnosed with breast infiltrating lobular carcinoma. During the imaging study with positron emission tomography-computerized tomography scan, a 4 cm solid lesion located in the chest wall was identified. Fine-needle aspiration followed by surgical excision with intraoperative frozen section study was performed. The combined histomorphologic, immunohistochemical, and molecular findings confirmed the diagnosis of AFH. In this report, we describe, to the best of our knowledge, the first patient with synchronous AFH and breast cancer.

An integrative histopathological and epigenetic characterization of primary intracranial mesenchymal tumors, FET:CREB-fused broadening the spectrum of tumor entities in comparison with their soft tissue counterparts

FET:CREB fusions have been described in a variety of tumors from various phenotypes. Recently, these fusion transcripts were reported in intracranial tumors, variably named intracranial mesenchymal myxoid tumors or angiomatoid fibrous histiocytomas. Controversy remains concerning the terminology for these tumors. Here, we report 11 cases of central nervous system mesenchymal tumors with proven FET:CREB fusion. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor or Sarcoma Classifier (v11b4/v12.2). However, by using unsupervised t‐SNE and hierarchical clustering analyses, six of the cases constituted a distinct cluster. The remaining four tumors showed no obvious relation to any of the other referenced classes but were close to the clusters of extra‐CNS angiomatoid fibrous histiocytomas (n = 1), clear cell sarcomas (n = 1), or solitary fibrous tumors (n = 2). Our findings confirm that intracranial FET:CREB‐fused tumors do not represent a single molecular tumor entity, although most samples clustered close to each other, indicating the existence of a distinct epigenetic group that could potentially be partially masked by the low number of cases included. Further analyses are needed to characterize intracranial FET:CREB fused‐defined tumors in more detail.

The spectrum of rare central nervous system (CNS) tumors with EWSR1-non-ETS fusions: experience from three pediatric institutions with review of the literature

The group of CNS mesenchymal (non‐meningothelial) and primary glial/neuronal tumors in association with EWSR1‐non‐ETS rearrangements comprises a growing spectrum of entities, mostly reported in isolation with incomplete molecular profiling. Archival files from three pediatric institutions were queried for unusual cases of pediatric (≤21 years) CNS EWSR1‐rearranged tumors confirmed by at least one molecular technique. Extra‐axial tumors and cases with a diagnosis of Ewing sarcoma (EWSR1‐ETS family fusions) were excluded. Additional studies, including anchored multiplex‐PCR with next‐generation sequencing and DNA methylation profiling, were performed as needed to determine fusion partner status and brain tumor methylation class, respectively. Five cases (median 17 years) were identified (M:F of 3:2). Location was parenchymal (n = 3) and undetermined (n = 2) with topographic distributions including posterior fossa (n = 1), frontal (n = 1), temporal (n = 1), parietal (n = 1) and occipital (n = 1) lobes. Final designation with fusion findings included desmoplastic small round cell tumor (EWSR1‐WT1; n = 1) and tumors of uncertain histogenesis (EWSR1‐CREM, n = 1; EWSR1‐CREB1, n = 1; EWSR1‐PLAGL1, n = 1; and EWSR1‐PATZ1, n = 1). Tumors showed a wide spectrum of morphology and biologic behavior. For EWSR1‐CREM, EWSR1‐PLAGL1 and EWSR1‐PATZ1 tumors, no significant methylation scores were reached in the known brain tumor classes. Available outcome (4/5) was reported as favorable (n = 2) and unfavorable (n = 2) with a median follow‐up of 30 months. In conclusion, we describe five primary EWSR1‐non‐ETS fused CNS tumors exhibiting morphologic and biologic heterogeneity and we highlight the clinical importance of determining specific fusion partners to improve diagnostic accuracy, treatment and monitoring. Larger prospective clinicopathological and molecular studies are needed to determine the prognostic implications of histotypes, anatomical location, fusion partners, breakpoints and methylation profiles in patients with these rare tumors.

Mesenchymal Tumors with EWSR1 Gene Rearrangements

Among the various genes that can be rearranged in soft tissue neoplasms associated with nonrandom chromosomal translocations, EWSR1 is the most frequent one to partner with other genes to generate recurrent fusion genes. This leads to a spectrum of clinically and pathologically diverse mesenchymal and nonmesenchymal neoplasms, variably manifesting as small round cell, spindle cell, clear cell or adipocytic tumors, or tumors with distinctive myxoid stroma. This review summarizes the growing list of mesenchymal neoplasms that are associated with EWSR1 gene rearrangements.

Treatment of angiomatoid fibrous histiocytoma after unplanned excision: a case report

Background

Angiomatoid fibrous histiocytoma (AFH) is a relatively uncommon soft tissue tumor of intermediate biologic potential. It occurs in subcutaneous regions of the extremities or the trunk, usually presenting in children or young adults. This is the first reported case of subcutaneous AFH that developed in the iliac region and was treated with an unplanned resection.

Case presentation

An 11-year-old girl noticed a small subcutaneous nodule in the iliac region. As the nodule was asymptomatic, it was observed naturally for a year, after which her parents consulted her doctor due to gradual growth of the nodule. The tumor was resected marginally without biopsy by a non-specialized surgeon. Based on the histology of the resected specimen, the tumor was suspected to be a sarcoma. The patient was referred to our hospital where we reinvestigated the histology of the tumor using immunohistochemistry. After confirming diagnosis of the tumor as an AFH, we undertook additional extensive resection in the iliac region where the tumor had developed. There was no evidence of tumor residue in the resected specimen. It has been 3 years since the operation, and there has been no evidence of recurrence.

Conclusion

We treated a case of AFH after unplanned resection. If subcutaneous tumors in the iliac region are detected, a diagnosis of AFH should be considered and a simple resection avoided.

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.

Angiomatoid Fibrous Histiocytoma With Prominent Myxoid Stroma: A Case Report and Review of the Literature

Angiomatoid fibrous histiocytoma is a rare neoplasm of intermediate malignant potential that usually occurs in the dermis or subcutaneous tissues of the extremities in children or young adults. It is characterized by a nodular growth of spindled, histiocytic, or epithelioid cells and blood-filled spaces, surrounded by a fibrous pseudocapsule that contains a lymphocytic cuff. The histological spectrum of this condition has expanded to include cases that contain prominent myxoid stroma. We herein present another instance of myxoid angiomatoid fibrous histiocytoma and review the clinical and histological features, immunohistochemical profile, and molecular genetics of this uncommon variant. We also discuss the diagnostic mimics of this condition, including benign myxoid soft tissue tumors and sarcomas, to illustrate the potential pitfalls in arriving at the diagnosis.

Angiomatoid fibrous histiocytoma: the current status of pathology and genetics

CONTEXT

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biologic potential and uncertain differentiation, most often arising in the superficial extremities of children and young adults. While it has characteristic histologic features of nodular distributions of ovoid and spindle cells with blood-filled cystic cavities and a surrounding dense lymphoplasmacytic infiltrate, there is a significant morphologic spectrum, which coupled with its rarity and lack of specific immunoprofile can make diagnosis challenging. Angiomatoid fibrous histiocytoma is associated with 3 characteristic gene fusions, EWSR1-CREB1 and EWSR1-ATF1, which are also described in other neoplasms, and rarely FUS-ATF1. Angiomatoid fibrous histiocytoma is now recognized at an increasing number of sites and is known to display a variety of unusual histologic features.

OBJECTIVE

To review the current status of AFH, discussing putative etiology, histopathology with variant morphology and differential diagnosis, and current genetics, including overlap with other tumors harboring EWSR1-CREB1 and EWSR1-ATF1 fusions.

DATA SOURCES

Review of published literature, including case series, case reports, and review articles, in online medical databases.

CONCLUSIONS

The occurrence of AFH at several unusual anatomic sites and its spectrum of morphologic patterns can result in significant diagnostic difficulty, and correct diagnosis is particularly important because of its small risk of metastasis and death. This highlights the importance of diagnostic recognition, ancillary molecular genetic confirmation, and close clinical follow-up of patients with AFH. Further insight into the genetic and epigenetic changes arising secondary to the characteristic gene fusions of AFH will be integral to understanding its tumorigenic mechanisms.

Molecular diagnostics complementing morphology in superficial mesenchymal tumors

Molecular techniques are increasingly important in the practice of surgical pathology. In soft tissue tumors, there are a number of tumors with recurring cytogenetic abnormalities. Knowledge of these abnormalities has furthered our understanding of these tumors and has also allowed development of molecular techniques to aid in the diagnosis. This review will focus on mesenchymal tumors with specific cytogenetic abnormalities that may present as a superficial tumor of the dermis or subcutis.

Subcutaneous angiomatoid fibrous histiocytoma mimicking metastatic melanoma

Angiomatoid fibrous histiocytoma is an uncommon soft-tissue tumor of intermediate malignancy that is often misdiagnosed initially. As there is not one immunohistochemical marker that consequently stains positive or negative for angiomatoid fibrous histiocytoma, molecular diagnostics are becoming more widely used. So far three translocations have been reported to arise in angiomatoid fibrous histiocytoma: FUS-ATF1, EWSR1-CREB1, or EWSR1-ATF1. We present a case of angiomatoid fibrous histiocytoma on the upper arm of a 40-year-old female, which was initially misdiagnosed as metastatic melanoma in a lymph node. Revision of the pathology revealed an angiomatoid fibrous histiocytoma, which was later confirmed by a EWSR1-CREB1 translocation with molecular diagnostics. Furthermore, we review the relevant literature and provide an overview of all available case reports in the past ten years. This case report illustrates the importance for pathologists of knowing the typical pathology features of AFH and integrating immunohistochemical and molecular findings in order to prevent overdiagnosis of lymph node metastasis of a malignancy.

Tumors with EWSR1-CREB1 and EWSR1-ATF1 fusions: the current status

EWSR1-CREB1 and EWSR1-ATF1 are gene fusions of which one or both have now been consistently described in 5 histopathologically and behaviorally diverse neoplasms: angiomatoid fibrous histiocytoma, conventional clear cell sarcoma (of tendons and aponeuroses), clear cell sarcoma-like tumor of the gastrointestinal tract, hyalinizing clear cell carcinoma of the salivary gland, and primary pulmonary myxoid sarcoma. Some of the tumors in this group have been described only recently, and others have been the subject of recent genetic insights contributing to their characterization. These neoplasms are all rare; yet, the increasing frequency with which EWSR1-CREB1 and EWSR1-ATF1 fusions are being described in separate entities is noteworthy. The additional molecular mechanisms by which tumors with such variable morphologic, immunohistochemical, and clinical phenotypes are generated are yet to be understood. We review the clinicopathologic and molecular features of this group of neoplasms unified by the presence of EWSR1-CREB1 and EWSR1-ATF1 genetic fusions.

Multinodular reticular schwannoma in the head and neck region: a potential diagnostic pitfall

Reticular/microcystic schwannoma is a recently described morphologic variant of schwannoma that occurs predominantly in visceral organs, most commonly the gastrointestinal tract. This report describes a case occurring in the masticator space, accompanied by focal erosion of the orbital floor, clinically and radiologically worrisome for malignancy. The 26-year-old man presented with facial swelling for 3 month. The tumor shows a multinodular appearance, with dense lymphoplasmacytic infiltrates in the fibrous septa. The tumor nodules are composed of plump spindle cells disposed in a reticular pattern. The diagnosis is confirmed by strong positive staining for S100 protein. The differential diagnoses of reticular schwannoma in the soft tissues of head and neck region are different from those in the gastrointestinal tract.

Angiomatoid fibrous histiocytoma: pleomorphic variant associated with multiplication of EWSR1-CREB1 fusion gene

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor which exceptionally occurs in visceral organs or bones. Histologically this is a bland, monomorphic tumor and only occasionally shows pleomorphism. Vast majority of the soft tissue cases share the same translocation and the resulting EWSR1-CREB1 gene fusion as background pathogenetic alteration. Here we report a 10-year-old boy with subcutaneous tumor of the right shoulder. Histological, immunohistochemical and FISH analyses of the case revealed pleomorphic phenotype, characteristic immunophenotype and multiplication of the EWSR1-CREB1 fusion gene in the nuclei of the tumor cells. The possible explanation of the fusion gene multiplication, its relation to the morphology and the clinical outcome are discussed in the context of the published literature.