Dermatofibrosarcoma protuberans COL1A1-PDGFB fusion is identified in virtually all dermatofibrosarcoma protuberans cases when investigated by newly developed multiplex reverse transcription polymerase chain reaction and fluorescence in situ hybridization assays

Multiple primary dermatofibrosarcoma protuberans tumors in a single patient with chromosomal microarray analysis: A case report and review

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous sarcoma with a high propensity for local invasion and recurrence. Although it is a rare event, the occurrence of multiple tumors in a single patient raises a diagnostic dilemma, as metastatic disease should be differentiated from multiple primary malignant events. In more than 90% of DFSP, a pathogenic t(17;22) translocation leads to the expression of COL1A1::PDGFB fusion transcripts. Karyotype analysis, fluorescence in situ hybridization, and RT-PCR can be useful ancillary studies in detecting this characteristic rearrangement, and sequencing of the fusion transcript can be used to support a clonal origin in metastatic and multifocal disease. However, previous reports have demonstrated variable sensitivity of these assays, in part due to the high sequence variability of the COL1A1::PDGFB fusion. Here, we report a patient who developed two distinct DFSP tumors over the course of 7 years. Chromosomal microarray analysis identified distinctive genomic alterations in the two tumors, supporting the occurrence of multiple primary malignant events.

Molecular Alterations in Pediatric Solid Tumors

Pediatric tumors can be divided into hematologic malignancies, central nervous system tumors, and extracranial solid tumors of bone, soft tissue, or other organ systems. Molecular alterations that impact diagnosis, prognosis, treatment, and familial cancer risk have been described in many pediatric solid tumors. In addition to providing a concise summary of clinically relevant molecular alterations in extracranial pediatric solid tumors, this review discusses conventional and next-generation sequencing-based molecular techniques, relevant tumor predisposition syndromes, and the increasing integration of molecular data into the practice of diagnostic pathology for children with solid tumors.

Dermatofibrosarcoma Protuberans: A Study of 148 Patients

INTRODUCTION

Dermatofibrosarcoma protuberans (DFSP) is the most common sarcoma of the skin. Although distant metastases are infrequent, DFSP is highly aggressive locally with frequent local recurrences. It has been reported that the presence within the tumour of areas histopathologically mimicking fibrosarcoma may increase the risk of recurrence.

OBJECTIVE

The objective of this study was to review the clinical features of our patients with DFSP and the factors associated with recurrence of the tumour, focussing on the presence of fibrosarcomatous areas.

METHODS

Retrospective study of patients with DFSP diagnosed in 1990-2021 in a tertiary university hospital. The medical records were reviewed to obtain the following data: age, sex, tumour location, diameter, evolution time, presence of fibrosarcomatous areas, development of recurrence, and follow-up. Factors possibly associated with disease-free survival were analysed with Kaplan-Meier method and multivariate Cox regression.

RESULTS

148 patients (74 women/74 men, mean age 46.28 years, SD 14.431) were included in the study. Tumours involved the head and neck in 15 cases, thorax in 31, abdomen in 16, upper back in 43, lower back in 10, upper extremities in 10, and lower extremities in 23. Fibrosarcoma-like areas were observed in 16 tumours (10.81%). In 17 patients (11.49%), recurrences were observed (13 local recurrences, 3 lung metastasis, and 1 local recurrence with lung metastasis). Fibrosarcomatous DFSP recurred more frequently than classic DFSP (50% vs. 6.82%, respectively), and its disease-free survival was significantly lower (p < 0.001). In multivariate Cox regression, the presence of fibrosarcomatous areas was the only factor influencing disease-free survival.

CONCLUSIONS

It is important to identify the fibrosarcomatous variant since it recurs more frequently and has lower recurrence-free survival. Distant metastases, mainly in the lung, are also more frequent in fibrosarcomatous DFSP.

Progressive insights into fibrosarcoma diagnosis and treatment: leveraging fusion genes for advancements

Fibrosarcoma, originating from fibroblast cells, represents a malignant neoplasm that can manifest across all genders and age groups. Fusion genes are notably prevalent within the landscape of human cancers, particularly within the subtypes of fibrosarcoma, where they exert substantial driving forces in tumorigenesis. Many fusion genes underlie the pathogenic mechanisms triggering the onset of this disease. Moreover, a close association emerges between the spectrum of fusion gene types and the phenotypic expression of fibrosarcoma, endowing fusion genes not only as promising diagnostic indicators for fibrosarcoma but also as pivotal foundations for its subcategorization. Concurrently, an increasing number of chimeric proteins encoded by fusion genes have been substantiated as specific targets for treating fibrosarcoma, consequently significantly enhancing patient prognoses. This review comprehensively delineates the mechanisms behind fusion gene formation in fibrosarcoma, the lineage of fusion genes, methodologies employed in detecting fusion genes within fibrosarcoma, and the prospects of targeted therapeutic interventions driven by fusion genes within the fibrosarcoma domain.

Gene fusions in superficial mesenchymal neoplasms: Emerging entities and useful diagnostic adjuncts

Cutaneous mesenchymal neoplasms are diagnostically challenging because of their overlapping morphology, and, often, the limited tissue in skin biopsy specimens. Molecular and cytogenetic techniques have identified characteristic gene fusions in many of these tumor types, findings that have expanded our understanding of disease pathogenesis and motivated development of useful ancillary diagnostic tools. Here, we provide an update of new findings in tumor types that can occur in the skin and superficial subcutis, including dermatofibrosarcoma protuberans, benign fibrous histiocytoma, epithelioid fibrous histiocytoma, angiomatoid fibrous histiocytoma, glomus tumor, myopericytoma/myofibroma, non-neural granular cell tumor, CIC-rearranged sarcoma, hybrid schwannoma/perineurioma, and clear cell sarcoma. We also discuss recently described and emerging tumor types that can occur in superficial locations and that harbor gene fusions, including nested glomoid neoplasm with GLI1 alterations, clear cell tumor with melanocytic differentiation and ACTIN::MITF translocation, melanocytic tumor with CRTC1::TRIM11 fusion, EWSR1::SMAD3-rearranged fibroblastic tumor, PLAG1-rearranged fibroblastic tumor, and superficial ALK-rearranged myxoid spindle cell neoplasm. When possible, we discuss how fusion events mediate the pathogenesis of these tumor types, and we also discuss the related diagnostic and therapeutic implications of these events.

Pediatric dermatofibrosarcoma protuberans: A clinicopathologic and genetic analysis of 66 cases in the largest institution in Southwest China

Background

Dermatofibrosarcoma protuberans (DFSP) is an uncommon cutaneous tumor in children. Most published articles are sporadic or small series and lack systematically molecular analyses. The aim of our study is to better understand the clinicopathologic and genetic features of these rare lesions.

Methods

All patients diagnosed with DFSP aged ≤ 18 years were retrospectively reviewed from January 2006 to May 2022.

Results

A total of 66 cases (32 male and 34 female patients) were identified, with ages ranging from 0.3 to 18 years (median, 13 years). Tumor locations predominantly occurred on the trunk (38/66, 57.6%), followed by the extremities (20/66, 30.3%) and head/neck (8/66, 12.1%). Histological findings revealed classic (41/66, 62.1%), myxoid (4/66, 6.1%), pigmented (6/66, 9.1%), plaque-like (3/66, 4.5%), giant cell fibroblastoma (GCF; 6/66, 9.1%), and fibrosarcomatous (6/66, 9.1%) variants of DFSP. Immunochemistry revealed minority tumors (9/66, 13.6%) showing patchy or negative staining for CD34. Fluorescence in situ hybridization (FISH) indicated that 49 of 53 tested cases including all detected biopsy specimens (11/11) contained COL1A1-PDGFB fusion, in which the average copy number gain of COL1A1-PDGFB was 0.68. There were four cases negative for COL1A1-PDGFB rearrangement, one of which was found to harbor a novel COL3A1-PDGFB fusion by next-generation sequencing (NGS). Treatment for 63 patients comprised 40 marginal excisions and 23 wide local excisions (WLEs), including 1 with imatinib therapy. Follow-up information was available on 49 patients with a duration of 12-161 months (median, 60 months). Fourteen patients developed tumor recurrence, all with initial marginal excisions. The others survived with no evidence of disease.

Conclusions

This study of pediatric DFSP indicates certain discrepancies in clinicopathologic characteristics between children and adults. The majority of pediatric DFSPs contain COL1A1-PDGFB fusion, the same as their adult counterparts. The COL3A1-PDGFB chimerism might be associated with the special morphology of GCF, which needs further investigation. FISH is valuable in biopsy tissues and cases with atypical CD34 immunostaining, while supplementary NGS could be helpful to identify the cytogenetically cryptic DFSP. Overall, an urgent accurate diagnosis is needed to formulate an optimal therapeutic strategy in the pediatric population.

Rare Variants of Dermatofibrosarcoma Protuberans: Clinical, Histologic, and Molecular Features and Diagnostic Pitfalls

Dermatofibrosarcoma protuberans (DFSP) is a dermal malignant mesenchymal tumor. Most variants are associated with a high risk of local recurrence and a low risk of metastasis. The classic histomorphology of this tumor is made up of uniform, spindle-shaped cells, arranged in a storiform pattern. Tumor cells characteristically infiltrate the underlying subcutis in a honeycomb pattern. Less common variants of DFSP have been identified: myxoid, pigmented, myoid, granular cell, sclerosing, atrophic, and fibrosarcomatous. Only the fibrosarcomatous variant has been shown to differ significantly from classic DFSP in terms of clinical outcome; fibrosarcomatous DFSP has been shown to be associated with a greater risk of local recurrence and metastatic potential than classic DFSP. However, the other variants may pose diagnostic difficulty as they resemble other types of spindle cell neoplasms, especially in small biopsy specimens. This article reviews the clinical, histologic, and molecular features of DFSP variants, as well as possible pitfalls in their diagnosis and how to resolve them.

The Role of BTBD7 in Normal Development and Tumor Progression

BTB/POZ domain-containing protein 7 (BTBD7) has a relative molecular weight of 126KD and contains two conserved BTB/POZ protein sequences. BTBD7 has been shown to play an essential role in normal human development, precancerous lesions, heat-stress response, and tumor progression. BTBD7 promotes branching morphogenesis during development and participates in the salivary gland, lung, and tooth formation. Furthermore, many studies have shown that aberrant expression of BTBD7 promotes heat stress response and the progression of precancerous lesions. BTBD7 has also been found to play an important role in cancer. High expression of BTBD7 affects tumor progression by regulating multiple pathways. Therefore, a complete understanding of BTBD7 is crucial for exploring human development and tumor progression. This paper reviews the research progress of BTBD7, which lays a foundation for the application of BTBD7 in regenerative medicine and as a biomarker for tumor prediction or potential therapeutic target.

Myxoid Dermatofibrosarcoma Protuberans of the Scrotum: Rare Tumor in an Uncommon Location

Background

Case Presentation

Conclusion

Genomic alterations of dermatofibrosarcoma protuberans revealed by whole-genome sequencing

Background

Dermatofibrosarcoma protuberans (DFSP) is a rare and marginal cutaneous sarcoma of intermediate‐grade malignancy, for which the genomic landscape remains unclear. Understanding the landscape of DFSP will help to further classify the genomic pathway of malignant development in soft tissue.

Objectives

To identify the comprehensive molecular pathogenesis of DFSP.

Methods

In this study, the comprehensive genomic features, with 53 tumour‐normal pairs of DFSP, were revealed by whole‐genome sequencing.

Results

The mutational signature 1 (C > T mutation at CpG dinucleotides) is featured in DFSP, resulting in higher mutations in DNA replication. Interestingly, the recurrence of DFSP is correlated with low tumour mutation burden. Novel mutation genes in DFSP were identified, including MUC4/6, KMT2C and BRCA1, and subsequently, three molecular subtypes of DFSP were classified on the basis of MUC4 and MUC6 mutations. Various structural aberrations including genomic rearrangements were identified in DSFPs, particularly in 17q and 22q, which cause oncogene amplification (AKT1, SPHK1, COL1A1, PDGFβ) or tumour suppressor deletion (CDKN2A/B). In addition to gene fusion of COL1A1‐PDGFβ [t(17;22)], we identified gene fusion of SLC2A5‐BTBD7 [t(1;14)] in DFSP through whole‐genome sequencing, and verified it experimentally. Enrichment analysis of altered molecules revealed that DNA repair, cell cycle, phosphoinositide 3‐kinase and Janus kinase pathways were primarily involved in DFSP.

Conclusions

This is the first large‐scale whole‐genome sequencing for DFSP, and our findings describe the comprehensive genomic landscape, highlighting the molecular complexity and genomic aberrations of DFSP. Our findings also provide novel potential diagnostic and therapeutic targets for this disease.

What is already known about this topic?

Chromosomal translocation between chromosome 17 and chromosome 22 is the main feature in the pathogenesis of dermatofibrosarcoma protuberans (DFSP).

What does this study add?

We describe the comprehensive genomic landscape of DFSP, highlighting the molecular complexity and genomic aberrations.

Our findings provide novel potential diagnostic and therapeutic targets for this disease.

What is the translational message?

Our study revealed novel molecular subtypes of DFSP based on genetic mutations, which benefits precision diagnosis.

We also found oncogene amplification, including AKT1 and SPHK1, which provides novel potential target molecules for further DFSP treatment.

In addition to gene fusion of COL1A1‐PDGFβ, we identified a novel gene fusion of SLC2A5‐BTBD7 in DFSP, which is a novel potential diagnostic and therapeutic target for this disease.

Dermatofibrosarcoma protuberans with platelet-derived growth factor-D rearrangement; two cases with morphologically distinct presentations

Dermatofibrosarcoma protuberans (DFSP) is a mesenchymal neoplasm that is usually located in the dermis or subcutis and is locally aggressive. Rarely, these lesions may undergo fibrosarcomatous transformation, which is thought to increase their metastatic potential. DFSP is classically associated with a 17;22 translocation (or ring chromosome thereof) resulting in fusion of the COL1A1 and PDGFB genes. However, variant fusions involving PDGFD have been recently reported. Herein, we present two morphologically diverse cases of DFSP with PDGFD rearrangement. Case 1 is a 68-year-old female with a left dorsal foot lesion. Morphologically, the lesion is unusual as it is a well-circumscribed, hypercellular, subcutaneous nodule with uniform CD34-positive spindle cells arranged in a herringbone pattern without storiform arrangement or "honeycombing" fat entrapment. It was diagnosed as pure fibrosarcomatous DFSP. Case 2 is a 37-year-old male with a right supra-auricular lesion. Morphologically, the lesion displays classic DFSP features including bland CD34-positive spindle cells with storiform growth, fat entrapment, and infiltrative borders. Both lesions were negative for COL1A1-PDGFB fusion but positive for PDGFD rearrangement by fluorescence in situ hybridization (FISH) analysis. FISH testing for PDGFD rearrangement should be performed in cases where there is a high suspicion for DFSP but initial studies for COL1A1-PDGFB are negative.

Determination of COL1A1-PDGFB breakpoints by next-generation sequencing in the molecular diagnosis of dermatofibrosarcoma protuberans

OBJECTIVE

In most cases, dermatofibrosarcoma protuberans (DFSP) is characterized by the chromosomal translocation t (17; 22) (q22; q13) that leads to a fusion of collagen type 1 alpha 1 (COL1A1) and platelet-derived growth factor beta chain (PDGFB). Recently, next-generation sequencing (NGS) has been reported to detect fusion transcripts in some malignancies. Therefore, the present study aimed to evaluate the utility of the targeted NGS in detecting the COL1A1-PDGFB fusion in patients with DFSP.

METHODS

We designed a targeted DNA capture panel to tile along the fusion regions, including exon, intron, and untranslated regions of the COL1A1 and PDGFB. A cohort of 18 DNA samples extracted from formalin-fixed, paraffin-embedded tissues was used to evaluate the targeted NGS. The results were compared with that of fluorescence in situ hybridization (FISH).

RESULTS

The COL1A1-PDGFB fusion was identified in 13 of 18 cases (72.2%) by targeted NGS assay. PDGFB breakpoints were constantly found in exon 2, while breakpoints in COL1A1 varied from exon 15 to 46. Of these 18 cases assayed by FISH, 12 (66.7%) exhibited COL1A1-PDGFB fusion signals. One case (P9), which was FISH-negative, was demonstrated with the fusion by targeted NGS and validated by PCR and Sanger sequencing. The targeted NGS results showed a high concordance with the results of the FISH assay (94.4%).

CONCLUSION

Our study reported a targeted NGS assay for detecting the breakpoints of the COL1A1-PDGFB fusion gene, which can be implemented in diagnosing patients with DFSP.

PDGFB RNA in situ hybridization for the diagnosis of dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a spindle cell neoplasm of the skin and superficial soft tissue with a tendency for locally aggressive behavior; metastatic potential coincides with fibrosarcomatous transformation. The vast majority of DFSPs harbor the t(17;22) translocation resulting in a COL1A1-PDGFB fusion that drives autocrine growth stimulation via PDGFB overexpression. Here, we examined the utility of PDGFB RNA chromogenic in situ hybridization (CISH) for the diagnosis of DFSP. A total of 337 tumors represented in whole tissue sections and tissue microarrays, including 37 cases of DFSP and 300 histologically similar spindle cell tumors, were subjected to PDGFB RNA CISH using commercially available probes. PDGFB overexpression was observed by light microscopy in 24 of 26 conventional DFSPs (92%) and 11 of 11 fibrosarcomatous DFSPs (100%). One of two DFSPs negative for PDGFB by RNA CISH was found to harbor an uncommon alternative rearrangement involving PDGFD. All examined cases of histologic mimics were negative for PDGFB overexpression; limited PDGFB expression, not reaching an empirical threshold of greater than 5 puncta or one aggregate of chromogen in more than 25% of cells, was observed in 7 of 300 mimics (2.3%), including desmoplastic melanoma, malignant peripheral nerve sheath tumor, angiosarcoma, and pleomorphic dermal sarcoma. Vascular PDGFB expression was seen in several tumor types. We conclude that PDGFB RNA CISH, with careful interpretation and the use of appropriate thresholds, may serve as a surrogate marker of PDGFB rearrangement and a useful ancillary tool for the diagnosis of DFSP.

Update on Superficial Spindle Cell Mesenchymal Tumors in Children

The diagnosis of cutaneous and subcutaneous spindle cell neoplasms in children is often challenging and has potential therapeutic and prognostic implications. Although correctly diagnosing dermatofibrosarcoma protuberans and infantile fibrosarcoma is paramount, pathologists should not ignore a number of diagnostic pitfalls linked to mostly rare tumors with completely different clinical outcomes. In the last decade, a spectrum of novel entities has been described; information from molecular biology has helped to shape this new landscape for spindle cell tumors. Here, we review the most noteworthy neoplasms in this spectrum, with a focus on their histological similarities: fibroblastic connective tissue nevus, medallion-like dermal dendrocyte hamartoma, or plaque-like CD34-positive dermal fibroma, which share features with fibrous hamartoma of infancy; lipofibromatosis and lipofibromatosis-like neural tumor; and plexiform myofibroblastoma, a recently described neoplasm that should be distinguished from plexiform fibrohistiocytic tumor. These tumors also have genetic similarities, particularly gene rearrangements involving NTRK3 or NTRK1. These genetic features are not only essential for the differential diagnosis of infantile fibrosarcoma but are also of diagnostic value for lipofibromatosis-like neural tumors. The more recently described RET, RAF1, and BRAF gene fusions are also discussed.

Molecular Alterations in Pediatric Solid Tumors

Pediatric tumors can be divided into hematologic malignancies, central nervous system tumors, and extracranial solid tumors of bone, soft tissue, or other organ systems. Molecular alterations that impact diagnosis, prognosis, treatment, and familial cancer risk have been described in many pediatric solid tumors. In addition to providing a concise summary of clinically relevant molecular alterations in extracranial pediatric solid tumors, this review discusses conventional and next-generation sequencing-based molecular techniques, relevant tumor predisposition syndromes, and the increasing integration of molecular data into the practice of diagnostic pathology for children with solid tumors.

Collagen Type I α-1 Promotes Malignant Glioma Cell Proliferation and Is Associated with Glioma Prognosis

Collagen type I α-1 chain (COL1A1) is closely involved in the advancement of various tumors, yet the role of COL1A1 in the progression of glioma is not clear. Herein, we evaluated the effect of COL1A1 on glioma cell proliferation. The effect of COL1A1 on glioma cell proliferation was assessed through overexpression or knockdown of COL1A1. The CCK-8 and colony formation assays, as well as immunohistochemistry (IHC) were used to detect COL1A1 expression in different glioma grades. U-87MG as well as U-251MG cells were stably-inserted with lentivirus containing COL1A1 through transfection, we additionally used qRT-PCR as well as Western blot assay to validate their overexpression efficiencies. COL1A1 mRNA and protein levels were upregulated in the high-grade glioma (HGG) compared to the low-grade glioma (LGG). COL1A1 IHC score was remarkably higher in HGG than LGG. The staining index (SI) further showed that COL1A1 protein levels were higher in HGG than LGG. The Kaplan–Meier analysis showed that elevated COL1A1 mRNA levels were obviously correlated with lower overall survival (OS) and disease-free survival (DFS) for brain glioma patients. COL1A1 mRNA and protein levels were markedly upregulated in human glioma cell lines when compared with brain astrocyte cell lines. The high expression level of COL1A1 facilitated glioma cell proliferation. COL1A1 knockdown remarkably inhibited glioma cell proliferation. Thus, this research shows that COL1A1 promotes glioma cell proliferation and is closely related to glioma prognosis.

Cutaneous Sarcomas

Cutaneous sarcomas represent a rare group of tumors presenting in the head and neck. In this article, we discuss specific sarcoma tumor types and their presentation, pathogenesis, histologic findings, and management recommendations. Tumors to be reviewed include dermatofibrosarcoma protuberans, atypical fibroxanthoma, pleomorphic dermal sarcoma, cutaneous leiomyosarcoma, and angiosarcoma.

Diagnostic Utility of a Custom 34-Gene Anchored Multiplex PCR-Based Next-Generation Sequencing Fusion Panel for the Diagnosis of Bone and Soft Tissue Neoplasms With Identification of Novel USP6 Fusion Partners in Aneurysmal Bone Cysts

CONTEXT.—

Bone and soft tissue tumors are heterogeneous, diagnostically challenging, and often defined by gene fusions.

OBJECTIVE.—

To present our experience using a custom 34-gene targeted sequencing fusion panel.

DESIGN.—

Total nucleic acid extracted from formalin-fixed, paraffin-embedded (FFPE) tumor specimens was subjected to open-ended, nested anchored multiplex polymerase chain reaction and enrichment of 34 gene targets, thus enabling detection of known and novel fusion partners.

RESULTS.—

During a 12-month period, 147 patients were tested as part of routine clinical care. Tumor percentage ranged from 10% to 100% and turnaround time ranged from 3 to 15 (median, 7.9) days. The most common diagnostic groups were small round blue cell tumors, tumors of uncertain differentiation, fibroblastic/myofibroblastic tumors, and adipocytic tumors. In-frame fusion transcripts were identified in 64 of 142 cases sequenced (45%): in 62 cases, the detection of a disease-defining fusion confirmed the morphologic impression; in 2 cases, a germline TFG-GPR128 polymorphic fusion variant was detected. Several genes in the panel partnered with multiple fusion partners specific for different diagnoses, for example, EWSR1, NR4A3, FUS, NCOA2, and TFE3. Interesting examples are presented to highlight how fusion detection or lack thereof was instrumental in establishing accurate diagnoses. Novel fusion partners were detected for 2 cases of solid aneurysmal bone cysts (PTBP1-USP6, SLC38A2-USP6).

CONCLUSIONS.—

Multiplex detection of fusions in total nucleic acid purified from FFPE specimens facilitates diagnosis of bone and soft tissue tumors. This technology is particularly useful for morphologically challenging entities and in the absence of prior knowledge of fusion partners, and has the potential to discover novel fusion partners.

Sarcoma and the 100,000 Genomes Project: our experience and changes to practice

The largest whole genome sequencing (WGS) endeavour involving cancer and rare diseases was initiated in the UK in 2015 and ran for 5 years. Despite its rarity, sarcoma ranked third overall among the number of patients' samples sent for sequencing. Herein, we recount the lessons learned by a specialist sarcoma centre that recruited close to 1000 patients to the project, so that we and others may learn from our experience. WGS data was generated from 597 patients, but samples from the remaining approximately 400 patients were not sequenced. This was largely accounted for by unsuitability due to extensive necrosis, secondary to neoadjuvant radiotherapy or chemotherapy, or being placed in formalin. The number of informative genomes produced was reduced further by a PCR amplification step. We showed that this loss of genomic data could be mitigated by sequencing whole genomes from needle core biopsies. Storage of resection specimens at 4 °C for up to 96 h overcame the challenge of freezing tissue out of hours including weekends. Removing access to formalin increased compliance to these storage arrangements. With over 70 different sarcoma subtypes described, WGS was a useful tool for refining diagnoses and identifying novel alterations. Genomes from 350 of the cohort of 597 patients were analysed in this study. Overall, diagnoses were modified for 3% of patients following review of the WGS findings. Continued refinement of the variant-calling bioinformatic pipelines is required as not all alterations were identified when validated against histology and standard of care diagnostic tests. Further research is necessary to evaluate the impact of germline mutations in patients with sarcoma, and sarcomas with evidence of hypermutation. Despite 50% of the WGS exhibiting domain 1 alterations, the number of patients with sarcoma who were eligible for clinical trials remains small, highlighting the need to revaluate clinical trial design.

Dermatofibrosarcoma protuberans in children and adolescents: The European Paediatric Soft Tissue Sarcoma Study Group prospective trial (EpSSG NRSTS 2005)

BACKGROUND

As dermatofibrosarcoma protuberans (DFSP) are rare with no prospective series within paediatric sarcoma trials, the European Paediatric Soft Tissue Sarcoma Study Group (EpSSG) examined the clinical data and outcomes of DFSP enrolled in a multinational study of non-rhabdomyosarcoma soft tissue sarcomas (NRSTS).

PATIENTS AND METHODS

Forty-six patients with confirmed DFSP were enrolled into the EpSSG NRSTS 2005 study. All had surgical resection and none had any further therapy at diagnosis.

RESULTS

The median age at diagnosis was 6.9 years (range 0.4-17.5). All patients had localised disease, and the majority had small <5 cm tumours (93%), and 76% had Intergroup Rhabdomyosarcoma Study (IRS) I tumours. All patients had up front surgery, 32 requiring two operations. There were 11 patients with IRS II tumours, of which only two went on to have a local recurrence. After a median follow up of 49.0 months (range 4.2-130.9), all patients were alive at the time of this report, with 5-year event-free survival of 92.6% (CI 78.8-97.6) with a 100% overall survival.

CONCLUSION

This report demonstrates the ability to run prospective paediatric studies in NRSTS in multiple European countries, with reasonable numbers of DFSP patients, with few events and no deaths, and hence excellent outcomes.

Dermatofibrosarcoma protuberans associated with trauma: A case report

A case of dermatofibrosarcoma protuberans (DFSP) in a 22-year old female associated with blunt trauma of the mid-upper back is presented in the current study with a review of the literature. DFSP is a rare slow growing sarcoma of the soft tissue most commonly seen on the trunk and upper extremities with a low to intermediate grade malignant potential, high chance of local invasion and a high local recurrence rate. The literature search revealed that both non-congenital mutation as well as trauma serve a role in the development of this dermal neoplasm, but the exact mechanism by which trauma may predispose to development of DFSP is unknown. However, it seems intuitive that chronic inflammation and stimulation of the immune system at a local level may trigger the immunopathologic changes that could lead to the malignant transformation of dermal cells. Future research into the relationship between trauma and DFSP on a cellular level is required, as there appears to be a direct link present.

Use of Fluorescence In Situ Hybridization (FISH) in Diagnosis and Tailored Therapies in Solid Tumors

Fluorescence in situ hybridization (FISH) is a standard technique used in routine diagnostics of genetic aberrations. Thanks to simple FISH procedure is possible to recognize tumor-specific abnormality. Its applications are limited to designed probe type. Gene rearrangements e.g., ALK, ROS1 reflecting numerous translocational partners, deletions of critical regions e.g., 1p and 19q, gene fusions e.g., COL1A1-PDGFB, genomic imbalances e.g., 6p, 6q, 11q and amplifications e.g., HER2 are targets in personalized oncology. Confirmation of genetic marker is frequently a direct indication to start specific, targeted treatment. In other cases, detected aberration helps pathologists to better distinguish soft tissue sarcomas, or to state a final diagnosis. Our main goal is to show that applying FISH to formalin-fixed paraffin-embedded tissue sample (FFPE) enables assessing genomic status in the population of cells deriving from a primary tumor or metastasis. Although many more sophisticated techniques are available, like Real-Time PCR or new generation sequencing, FISH remains a commonly used method in many genetic laboratories.

Overview of « druggable » alterations by histological subtypes of sarcomas and connective tissue intermediate malignancies

We summarize herein the literature data about molecular targeted therapies in sarcomas and conjunctive tissue intermediate malignancies. For each clinical setting, the level of evidence, the mechanism of action and the target are described. The two major axes include (i) identification of subgroups of tumors with druggable alteration irrespective of the histological diagnosis (e.g. NTRK), and (ii) druggable target of pathway related to the physiopathology of the tumor: denosumab and bone giant cell tumor, imatinib and soft tissue giant cell tumor, mTOR inhibitor and PECOMA.

Unmasking dermatofibrosarcoma protuberans: Case report of an atypical presentation complicated by post-surgical excision

INTRODUCTION

Dermatofibrosarcoma Protuberans (DFSP) is a rare type of malignant tumor of the cutaneous soft tissue that typically involves the dermis and surrounding structures. The typical clinical presentation involves an asymptomatic, slowly enlarging, indurated plaque, usually found on the trunk.

PRESENTATION OF CASE

Here we present an atypical presentation of DFSP in a patient with a recurrent mass that was initially diagnosed as a lipoma, with supporting literature and clinical considerations for post-surgical management DISCUSSION: In its earlier stages, DFSP can mimic other benign or malignant dermatological pathologies, which can complicate diagnosis purely via history and physical exam. Atypical features such as prior surgical management, morphology, and location can complicate the clinical diagnosis of DFSP. Immunohistochemistry is often required for definitive diagnosis as DFSP is CD34+ and is histologically described as spindle-cells in whorled or storiform pattern, with uniform, small elongated cells.

CONCLUSION

DFSP is a rare tumor of the skin and subcutaneous tissue. Though it commonly presents with induration, skin discoloration, and telangiectasias, it is important to keep DFSP as a differential in new masses found on previous surgical sites, especially if the previous mass had a possibility of recurrence.

An Overview of Uncommon Cutaneous Malignancies, Including Skin Appendageal (Adnexal) Tumours and Sarcomas

A standardised classification of malignant skin appendageal (adnexal) tumours and sarcomas is required for improved patient management and prognosis. This has been hindered by considerable morphological variation both within and between tumour types, the use of many synonyms for the same tumour types and variation in classification between pathologists. This update uses the improved classification in the 2018 WHO classification of skin tumours as the basis to discuss malignant skin appendageal tumours, sarcomas and cutaneous metastases that regularly present to skin cancer clinicians, multidisciplinary skin cancer teams and tumour boards, with current evidence for management, where appropriate.

PDGFB Rearrangements in Dermatofibrosarcoma Protuberans of the Vulva: A Study of 11 Cases Including Myxoid and Fibrosarcomatous Variants

Dermatofibrosarcoma protuberans (DFSP) is a low-grade fibroblastic sarcoma that tends to arise in young to middle age adults and involve the trunk and proximal extremities. Rare examples of vulvar DFSP have been reported, including myxoid, myoid, and fibrosarcomatous variants, but detection of the characteristic t(17;22)(q22;q13) that produces COL1A1-PDGFB gene fusion has not been evaluated in a large series of primary vulvar tumors. The clinical, morphologic, immunohistochemical, and molecular cytogenetic features of 11 cases were examined. Patient age ranged from 29 to 75 yr (mean, 46 yr; median, 43 yr). Seven tumors were purely classic DFSP, 1 was purely myxoid DFSP and the remaining 3 had varying quantities of fibrosarcomatous DFSP. All cases of classic DFSP had diffuse expression of CD34 and low-level p53 immunoreactivity. Myxoid variants had strong, but reduced expression of CD34. Fibrosarcomatous DFSP showed focal CD34 expression and increased p53 reactivity. Nine of 11 tumors (82%) had rearrangement of PDGFB by fluorescence in situ hybridization. The 2 nonrearranged tumors were a classic DFSP and a myxoid DFSP with fibrosarcomatous transformation. Follow-up was available for 9 patients (82%) and ranged from 1 to 108 mo (mean, 30 mo; median, 21 mo). Eight patients had tumors with positive margins, one of which developed local recurrence after no further therapy. No patient developed metastasis. The high frequency of PDGFB rearrangement in vulvar DFSP provides a useful exploit in diagnostically challenging cases and genetic evidence of probable clinical response to targeted therapeutics in cases of locally advanced or metastatic tumors.

Alternative PDGFD rearrangements in dermatofibrosarcomas protuberans without PDGFB fusions

Dermatofibrosarcoma protuberans is underlined by recurrent collagen type I alpha 1 chain-platelet-derived growth factor B chain (COL1A1-PDGFB) fusions but ~ 4% of typical dermatofibrosarcoma protuberans remain negative for this translocation in routine molecular screening. We investigated a series of 21 cases not associated with the pathognomonic COL1A1-PDGFB fusion on routine fluorescence in situ hybridization (FISH) testing. All cases displayed morphological and clinical features consistent with the diagnosis of dermatofibrosarcoma protuberans. RNA-sequencing analysis was successful in 20 cases. The classical COL1A1-PDGFB fusion was present in 40% of cases (n = 8/20), and subsequently confirmed with a COL1A1 break-apart FISH probe in all but one case (n = 7/8). 55% of cases (n = 11/20) displayed novel PDGFD rearrangements; PDGFD being fused either to the 5' part of COL6A3 (2q37.3) (n = 9/11) or EMILIN2 (18p11) (n = 2/11). All rearrangements led to in-frame fusion transcripts and were confirmed at genomic level by FISH and/or array-comparative genomic hybridization. PDGFD-rearranged dermatofibrosarcoma protuberans presented clinical outcomes similar to typical dermatofibrosarcoma protuberans. Notably, the two EMILIN2-PDGFD cases displayed fibrosarcomatous transformation and homozygous deletions of CDKN2A at genomic level. We report the first recurrent molecular variant of dermatofibrosarcoma protuberans involving PDGFD, which functionally mimic bona fide COL1A1-PDGFB fusions, leading presumably to a similar autocrine loop-stimulating PDGFRB. This study also emphasizes that COL1A1-PDGFB fusions can be cytogenetically cryptic on FISH testing in a subset of cases, thereby representing a diagnostic pitfall that pathologists should be aware of.

A novel case of an aggressive superficial spindle cell sarcoma in an adult resembling fibrosarcomatous dermatofibrosarcoma protuberans and harboring an EML4-NTRK3 fusion

A subset of soft tissue sarcomas often harbors recurrent fusions involving protein kinases. While some of these fusion events have shown utility in arriving at a precise diagnosis, novel fusions in otherwise difficult to classify sarcomas continue to be identified. We present a case of a 40-year-old female who noted a lower back nodule in 2010 that was initially labeled as a dermatofibrosarcoma protuberans with fibrosarcomatous transformation. The lesion recurred the following year and metastasized to the groin 6 years later. Because of some morphologic peculiarities, molecular characterization was pursued in the metastatic focus, which revealed the neoplasm was negative for the COL1A1-PDGFB fusion. However, anchored multiplex polymerase chain reaction for targeted next-generation sequencing (Archer Dx) detected an EML4-NTRK3 fusion, which was confirmed by reverse transcription-PCR, Sanger sequencing and RNA sequencing analysis of the recurrent and metastatic specimens. Although various soft tissue neoplasms involving fusions with NTRK genes are well-reported, the current case could not be easily classified in any of the established entities. Nevertheless, it raises interesting questions regarding the importance of classification, prognosis, and treatment for some of these tyrosine kinase fusion-driven sarcomas.

Applications of Ancillary Testing in the Cytologic Diagnosis of Soft Tissue Neoplasms

Soft tissue neoplasms are diagnostically challenging, although many advances in ancillary testing now enable accurate classification of fine-needle aspiration biopsies by detection of characteristic immunophenotypes (including protein correlates of molecular alterations) and molecular features. Although there are many useful diagnostic immunohistochemical markers and molecular assays, their diagnostic utility relies on correlation with clinical and morphologic features, judicious application, and appropriate interpretation because no single test is perfectly sensitive or specific. This review discusses applications of ancillary testing for commonly encountered soft tissue neoplasms in cytopathologic practice in the context of a pattern-based approach.

Dermatofibrosarcoma protuberans with a novel COL6A3-PDGFD fusion gene and apparent predilection for breast

Dermatofibrosarcoma protuberans is a locally aggressive superficial mesenchymal neoplasm. It typically occurs in adulthood, and has been reported to have a slight male predilection. Tumors have a characteristic histopathologic appearance, including: storiform architecture, infiltrative "honeycomb" growth within subcutaneous adipose tissue, and immunoreactivity for CD34. Virtually all molecularly characterized cases to date have been found to harbor a COL1A1-PDGFB fusion product. Following identification of an index patient with a novel COL6A3-PDGFD fusion gene, we undertook a molecular investigation, using a combination of RNA sequencing and fluorescence in situ hybridization (FISH), to assess the prevalence of PDGFD rearrangement in dermatofibrosarcoma protuberans (N = 63). Three additional patients were found to have balanced PDGFD rearrangements. Interestingly, all 4 tumors arose on the breast of females. As a result, we subsequently examined 16 additional cases of primary breast dermatofibrosarcoma protuberans, identifying 2 additional tumors with PDGFD rearrangement. The morphology and immunophenotype of all 6 cases was analogous to those with the canonical COL1A1-PDGFB fusion; none of the cases showed fibrosarcomatous transformation. This study illustrates that the COL6A3-PDGFD fusion product is rare in dermatofibrosarcoma protuberans, and associated with an apparent predilection for breast. An awareness of this variant is important for pathologists, as it will not be detected using conventional reverse transcription polymerase chain reaction or FISH-based diagnostic assays for dermatofibrosarcoma protuberans.

Cutaneous Spindle Cell Neoplasms: Pattern-Based Diagnostic Approach

Context.—

Spindle cell neoplasms arising in the skin comprise a heterogeneous group of tumors with divergent lineages. Cutaneous spindle cell neoplasms are relatively common and present surgical pathologists with diagnostic challenges. Recognition of their histopathologies is important for correct diagnosis and management. The current review presents a pattern-based diagnostic approach to common cutaneous spindle cell neoplasms that often cause diagnostic difficulties.

Objective.—

To provide a useful guide for diagnosis of cutaneous spindle cell neoplasms.

Data Sources.—

PubMed (US National Library of Medicine) reports and the authors' personal experiences are reviewed.

Conclusions.—

The authors briefly summarize the histologic features and differential diagnoses of common cutaneous spindle cell neoplasms.

Guidelines for Diagnosis and Treatment of Cutaneous Sarcomas: Dermatofibrosarcoma Protuberans

Sarcomas comprise a broad group of tumors, many of whose biological behavior and aggressiveness differ from one type to another. The therapeutic approach is generally multidisciplinary and often complex. Developments in surgical and oncological dermatology during the last few decades have positioned dermatologists as specialists in the diagnosis and treatment of skin cancer. The aim of this article is to review the main soft tissue sarcomas that typically affect the skin. Dermatofibrosarcoma protuberans is a low-grade malignant sarcoma. It exhibits slow-growth, is locally invasive, and has low metastatic potential (<3%). Mohs micrographic surgery is the treatment of choice. The COL1A1-PDGFB translocation should be analyzed in cases of unclear diagnosis and when it is necessary to identify candidates for tyrosine kinase inhibitors. Imatinib is indicated for the treatment of locally advanced and metastatic dermatofibrosarcoma protuberans.

Dedifferentiated Solitary Fibrous Tumor: A Concise Review

Solitary fibrous tumor (SFT) is a unique mesenchymal neoplasm that was originally believed to be of submesothelial origin. Eventually, SFT expanded to include what was previously called hemangiopericytoma in other regions of the body that had similar immunohistochemical and morphologic features. Although most are benign, many studies have tried to identify histologic features that predict which tumors will behave in an aggressive manner. Recently, dedifferentiation has been described in rare cases of SFT and does appear to correlate with a more aggressive clinical course. Dedifferentiated SFT occurs in a similar age range and location as conventional SFT and can resemble multiple different malignant entities. Utilization of ancillary studies and thorough tissue sampling is important to reach the correct diagnosis. The morphologic features, immunohistochemistry, molecular alterations, and prognosis will be discussed.

A favorable outcome of advanced dermatofibrosarcoma protuberans under treatment with sunitinib after imatinib failure

While traditional cytotoxic agents play a limited role in advanced dermatofibrosarcoma protuberans (DFSP), the treatment of sunitinib for patients with advanced DFSP after imatinib failure is not well defined. The objective of this case report was to analyze the relationship between molecular mechanisms and clinical outcomes of sunitinib treatment in patients with advanced DFSP after imatinib failure. In this case report, a 37-year-old man suffered from advanced DFSP progression after surgical operation, microwave ablation, and chemotherapy. The immunohistochemistry in this patient revealed abundant expression of platelet-derived growth factor receptor-beta on tumor cells, which is one of the drug targets of sunitinib. The nucleotide sequence analysis revealed COL1A1-PDGFB fusion transcripts in this patient. Thus, we treated the patient with sunitinib, a multi-targeted tyrosine kinase inhibitor, after imatinib failure. After treatment with sunitinib, the patient exhibited a partial response and 9 months’ progression-free survival without significant adverse drug effects. In our case, the patient with advanced DFSP experienced a favorable outcome in 9-months’ progression-free survival and a significant improvement of quality of life without serious side effects after sunitinib treatment. Therefore, sunitinib could serve as another treatment option for patients with advanced DFSP.

Kutane Sarkome

Cutaneous sarcomas comprise a heterogeneous group of mesenchymal spindle cell tumors of the dermis and subcutis, one of the best-known entities being dermatofibrosarcoma protuberans. Other sarcomas addressed in this review include a typical fibroxanthoma, cutaneous undifferentiated pleomorphic sarcoma, leiomyosarcoma, liposarcoma, and angiosarcoma. With the exception of dermatofibrosarcoma protuberans, which has its peak incidence in middle-aged adults, cutaneous sarcomas usually occur in elderly individuals starting in the sixth or seventh decade of life. The pathogenesis of the various disease entities is not uniform and has not been definitively ascertained. Histology is the key to arriving at a correct diagnosis, and should always include ruling out other dermal neoplasms such as melanoma. In recent years, molecular genetic methods have provided greater insight into the pathogenesis, thus paving the way for new targeted therapies. Treatment of choice for cutaneous sarcomas is excision with sufficient surgical margins. Adjuvant and neoadjuvant therapeutic concepts include radiation therapy and the use of targeted therapies or chemotherapies. Local recurrences have frequently been reported in cutaneous sarcomas. Unlike soft tissue sarcomas, the prognosis in terms of survival - with the exception of angiosarcoma - is very good if treated adequately, a fact that should be emphasized to patients.

Pathology of Melanotic Schwannoma

CONTEXT.—

Melanotic schwannoma (MS) is a nerve sheath tumor with a uniform composition of variably melanin-producing Schwann cells and metastatic potential. The MS is an uncommon neoplasm, accounting for less than 1% of all nerve sheath tumors, with a predilection for spinal nerve involvement. Microscopically, the tumors are characterized by spindle and epithelioid cells arranged in interlacing fascicles, with marked accumulation of melanin in neoplastic cells and associated melanophages. The MSs are frequently associated with Carney complex, showing features of psammoma bodies and adipose-like cells. Strict criteria of malignancy in MS are not well developed, although a combination of worrisome histologic features (large, vesicular nuclei, with macronucleoli, brisk mitotic activity, and necrosis) raises concern for aggressive behavior.

OBJECTIVE.—

To review the current status of the MS literature, discussing putative etiology, histopathology, current genetics, and differential diagnoses, including overlap with other pigmented tumors.

DATA SOURCES.—

Search of PubMed (National Center for Biotechnology Information, Bethesda, Maryland) and the authors' own experiences.

CONCLUSIONS.—

The occurrence of MS 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 high tendency to recur locally and to metastasize, which highlights the importance of diagnostic recognition, ancillary molecular genetic testing, and close clinical follow-up of patients with MS.