Low-grade Fibromyxoid Sarcoma of the Small Intestine: Report of 4 Cases With Molecular Cytogenetic Confirmation

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.

Superficial low-grade fibromyxoid sarcoma

BACKGROUND

Low-grade fibromyxoid sarcoma (LGFMS) typically involves deep soft tissue (beneath the fascia) of the proximal extremities and trunk. Long-term follow-up has shown a high rate of local recurrence, metastasis, and death. To the best of our knowledge, there is only one previous large series focusing on superficial LGFMS suggesting superficial tumors are disproportionately more common in children and may have a better prognosis. Our study's primary goals are to confirm these findings and increase general awareness that LGFMS may arise in superficial soft tissue.

METHODS

We retrieved our cases of superficial LGFMS diagnosed between 2008 and 2020. Available slides were reviewed, and clinical data and follow-up information were obtained.

RESULTS

The patients included nine males and 14 females with a median age of 29 years; eight (35%) were children (<18 years) and five (22%) were young adults (18-30 years). The majority involved the lower extremities (65%). The tumors were primarily centered in the subcutis (91%) and dermis (9%). Microscopically, they had typical features of LGFMS with alternating fibrous and myxoid zones composed of bland, slightly hyperchromatic spindled cells. All were positive for MUC4 by immunohistochemistry and/or FUS rearrangement by FISH. Follow-up on 14 cases ranged from 11 to 148 months (median 61 months) with no evidence of recurrences or distant metastases.

CONCLUSIONS

Compared to conventional deep-seated counterparts, superficial LGFMS is more likely to occur in the extremities of children and young adults and may have a better clinical outcome. Further studies with longer follow-up will likely help support these findings.

Malignant melanotic Xp11 neoplasms exhibit a clinicopathologic spectrum and gene expression profiling akin to alveolar soft part sarcoma: a proposal for reclassification

The classification of the distinct group of mesenchymal neoplasms, first described as 'Xp11 translocation perivascular epithelioid cell tumor (PEComa)' and for which the term 'melanotic Xp11 neoplasm' or 'Xp11 neoplasm with melanocytic differentiation' has recently been proposed, remains challenging and controversial. We collected 27 melanotic Xp11 neoplasms, the largest series to date, for a comprehensive evaluation. Fourteen of the cases, together with eight alveolar soft part sarcomas (ASPS), nine conventional PEComas and a control group of seven normal tissues were submitted to RNA sequencing. Follow-up available in 22 patients showed 5-year overall survival and 5-year disease-free survival of 47.6 and 35.7%, respectively, which were similar to ASPS and significantly worse than conventional PEComa. Univariate analysis of location (occurring in the kidney versus not kidney), infiltrative growth pattern, nuclear pleomorphism, mitotic activity ≥2/50 high-power fields (HPF), necrosis and lymphovascular invasion were found to be associated with overall survival and/or disease-free survival. Multivariate analysis identified that location was the only factor found to independently correlate with disease-free survival. More importantly, RNA sequencing-based clustering analysis segregated melanotic Xp11 neoplasm and ASPS from other tumors, including conventional PEComa and Xp11 translocation renal cell carcinoma, and formed a compact cluster representative of the largely similar expression signature. Here we clearly define the true biologic nature of melanotic Xp11 neoplasms which are distinctive malignant mesenchymal tumors, rather than simply PEComa variants with occasionally unpredictable behavior. Meanwhile, melanotic Xp11 neoplasm and ASPS more likely represent phenotypic variants of the same entity, which is distinct from conventional PEComa and Xp11 translocation renal cell carcinoma. Based on these important findings, melanotic Xp11 neoplasm might be reclassified into a distinctive entity together with ASPS, independent from PEComa, in future revisions of the current WHO categories of tumors of soft tissue and bone for the improved reclassification. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Low-grade fibromyxoid sarcoma: A report of the Cooperative Weichteilsarkom Studiengruppe (CWS)

BACKGROUND

Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft-tissue tumor with benign histologic appearance, though fully malignant behavior is possible.

METHODS

Patients with LGFMS <21 years registered in Cooperative Weichteilsarkom Studiengruppe trials until 2017 were analyzed. Firstline treatment consisted of complete surgical resection whenever possible.

RESULTS

Median age of 31 patients was 10.9 years (first month to 17.1 years). Twenty-six tumors were confirmed to the tissue of origin (T1), four invaded contiguous structures (T2), one was TX. Eight were >5 cm. The best surgical result was resection with free margins (R0) in 24 and microscopic residuals (R1) in seven. Five-year event-free (EFS), 5-year local-relapse-free (LRFS), and 5-year overall-survival were 71 ± 18.6% confidence interval (CI) 95%, 76 ± 17.6% CI 95%, and 100%, respectively. Six patients suffered local relapse in a median of 1 year, one combined within 1.3 year and one metastatic relapse with lesions in the lung, back muscles, and thigh discovered in whole-body imaging 6 years after the first diagnosis. In univariate analysis, T status correlated with EFS (T1 79.6 ± 18.6%, T2 50.0 ± 49.0%, P = .038). Resection with free margins tends to be associated with better LRFS (R0 82.4 ± 18.6%, R1 53.6 ± 39.4%, P = .053). Among 24 patients with R0 resection, five (21%) suffered relapse, thereof three local, one metastatic, and one combined. Among seven patients with R1-resection, three (43%) suffered local relapse.

CONCLUSION

Special caution is advisable in T2 tumors. The metastatic potential with lesions in unusual sites indicates that affected patients need to be informed. If long-term follow-up with whole-body imaging is beneficial, it may be addressed in larger intergroup analyses. Further research in disease biology is essential for optimal treatment and follow-up care.

Huge mesenteric low-grade fibromyxoid sarcoma: A case report and review of the literature

Low-grade fibromyxoid sarcoma is a rare soft tissue tumor which has been mostly reported in lower extremities; however, it can also occur in other parts of the body such as head and neck and abdominal wall, but its occurrence in the abdominal cavity and mesentery of bowel is an extremely rare event and has very rarely been reported. Herein, we report our experience with a 24-year-old lady with a huge mesenteric mass, turned out to be low-grade fibromyxoid sarcoma. This case is the largest one reported in the English literature. We will also discuss about the previously reported cases of low-grade fibromyxoid sarcoma in the English literature.

Abdominopelvic and Retroperitoneal Low-Grade Fibromyxoid Sarcoma: A Clinicopathologic Study of 13 Cases

OBJECTIVES

Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor often arising in the lower extremities. Only rare examples in the abdominal cavity, pelvis, and retroperitoneum have been reported.

METHODS

cases of abdominopelvic and retroperitoneal LGFMS were retrieved. MUC4, Actin, ALK, β-catenin, desmin, DOG1, KIT, S100 protein, and STAT6 testing was performed, and a subset was tested for FUS rearrangement.

RESULTS

Sites included intra-abdominal/abdominal wall (four cases), retroperitoneum (three cases), pelvis (three cases), small bowel (two cases), and kidney (one case) (median size, 15 cm; age range, 5-61 years). Tumors harbored spindled cells with mild to moderate atypia, displaying alternating myxoid nodules and hyalinized areas. All cases were positive for MUC4, and five (of five) cases tested harbored FUS rearrangement. Variable positivity for DOG1 (four of 10) and actin (two of 10) was identified. Six tumors recurred, and one patient developed metastasis.

CONCLUSION

LGFMS arising in these central locations exhibits similar clinicopathologic features to its counterpart in the extremities. LGFMS at these sites may show limited immunoreactivity for DOG1 and actin.

Low-grade fibromyxoid sarcoma of the external anal sphincter: a case report

BACKGROUND

Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft tissue tumor that has a tendency to grow in the deep soft tissue of the trunk and extremities. Despite its benign appearance, the tumor has a high recurrence rate and metastatic potential. LGFMS in the perineal space is rare, and only a few cases have been reported. We present the first case of LGFMS to be located at the external anal sphincter.

CASE PRESENTATION

A 27-year-old male patient admitted to our Surgical Department with perianal pain and swollen for a year. The digital rectal examination revealed a perianal mass. Oral metronidazole and analgesia were prescribed on suspicion of perianal abscess failed to alleviate the symptom; hence, the patient was scheduled for surgery. Intraoperative diagnosis revealed an encapsulated tumor in the external anal sphincter that extended from the perianal region orally to the pararectal space. The results of immunohistochemistry (MUC4 staining) and FUS gene rearrangement by fluorescence in situ hybridization confirmed the diagnosis of LGFMS.

CONCLUSIONS

This case is unique in terms of the location of the rare soft tissue tumor. Although LGFMS is considered low grade, its unpredictable behavior necessitates a long-term follow-up.

DOG1 Expression in Low-Grade Fibromyxoid Sarcoma

DOG1 is a highly sensitive marker for gastrointestinal stromal tumor (GIST) and is in the routine diagnostic antibody repertoire of many surgical pathology laboratories. Moreover, GIST is well recognized by both pathologists and clinicians in the differential diagnosis of intra-abdominal and pelvic neoplasms. Low-grade fibromyxoid sarcoma (LGFMS) is, however, much less frequently anticipated, particularly when occurring at unusual sites, because of its rarity and bland histology, particularly on core biopsy. We describe a case of a 53-year-old male with a large pelvic and pararectal mass, which on biopsy showed a moderately cellular spindle cell neoplasm within fibrous stroma. Immunohistochemistry at the referring center showed diffuse and strong expression of DOG1 with negativity for other markers. After referral to a tertiary center, repeat DOG1 immunohistochemistry again showed diffuse expression, but MUC4 was also positive, and this was confirmed to be LGFMS, harboring FUS-CREB3L2 fusion transcripts by reverse transcription-polymerase chain reaction and FUS rearrangement with fluorescence in situ hybridization. In view of this we assessed DOG1 expression in 10 other LGFMS (all MUC4 positive, and 9 molecularly confirmed to harbor FUS-CREB3L2 fusion transcripts and/or FUS or EWSR1 gene rearrangement), of which 5 showed DOG1 expression in up to 75% of tumor cells, varying in intensity from weak to strong. While LGFMS and GIST are generally morphologically dissimilar, less typical variants of each exist, and both can contain bland spindled cells within fibrous stroma. As the morphologic spectrum of LGFMS is wide, and as it can occur in unusual sites and may not be well recognized by general pathologists and non–soft tissue pathologists, we highlight the potential for diagnostic confusion with GIST owing to aberrant DOG1 expression. This is clinically pertinent, as the management and prognosis of these 2 neoplasms differs significantly.

Diffuse intra-abdominal low grade fibromyxoid sarcoma with hepatic metastases: Case report and review of the literature

Introduction

Low grade fibromyxoid sarcoma (LGFMS)1 is a rare soft tissue tumor involving deep soft tissues of the extremities and trunk. Abdominal location is extremely uncommon in which the few cases published in the literature are characterized by slow tumoral progression and long recurrence-free intervals.

Methods

We report the first case of an intra-abdominal LGFMS which was discovered incidentally in a 42-year-old woman presenting diffuse peritoneal nodules and hepatic metastasis on CT and MRI scans.

Results

The patient was successfully treated through conservative measures and remained asymptomatic at the 48 month follow-up.

Conclusions

This is the first reported case of LGFMS with peritoneal and hepatic metastases. Despite the discovery of an advance disease at exploration, the patient who refused a major surgical operation presents an uneventful follow-up and long term survival.

Fibrosarcoma: a review and update

Adult fibrosarcoma, defined by the World Health Organization as a 'malignant neoplasm composed of fibroblasts with variable collagen production and, in classical cases, a "herringbone" architecture', is a very rare soft tissue sarcoma. Once considered the most common adult sarcoma, the incidence of adult fibrosarcoma has declined dramatically over the past several decades. This is due to (i) evolution in the classification of soft tissue tumours (ii) recognition of clinically, morphologically and genetically distinctive subtypes of fibrosarcoma and (iii) increased understanding of the many other mesenchymal and non-mesenchymal tumours that may mimic fibrosarcoma. This review article will summarize the current state of our knowledge about strictly defined adult fibrosarcoma and discuss important entities in its differential diagnosis, including various fibrosarcoma variants, monophasic synovial sarcoma and other potential mesenchymal and non-mesenchymal mimics.

Plexiform fibromyxoma (plexiform angiomyxoid myofibroblastic tumor) of stomach: an unusual presentation as a fistulating abscess

Plexiform fibromyxoma (plexiform angiomyxoid myofibroblastic tumor) is a rare benign mesenchymal tumor of stomach. The plexiform growth of bland-looking spindly cells in a richly vascularized fibromyxoid stroma is distinctive. The described cases are solid tumors associated with ulceration, with the patients presenting with symptoms related to the ulcer or mass effect of the tumor. We report an unusual case presenting as a fistulating abscess. A 42-year-old woman presented with abdominal pain, fever, and elevated white cell count. Computed tomography scan revealed a 12-cm cavitating mass in the gastric antrum, with fistulation to the gastric lumen through an ulcer. Histologic examination showed transmural involvement of the stomach by plexiform islands of fibromyxoid tumor with interspersed delicate capillaries. There was a pseudocyst-like component. The unusual presentation therefore broadens the clinical and pathologic spectrum of this rare tumor type.

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.