Inconspicuous insertion 22;12 in myxoid/round cell liposarcoma accompanied by the secondary structural abnormality der(16)t(1;16)

A cryptic EWSR1::DDIT3 fusion in myxoid liposarcoma: Potential pitfalls with FISH and cytogenetics

Myxoid liposarcoma (MLS) is molecularly characterized by fusions involving the DDIT3 gene in chromosome band 12q13; the fusion partner is FUS in band 16p11 in 90-95% of the cases and EWSR1 in band 22q12 in the remaining 5-10%. Hence, molecular studies, often fluorescence in situ hybridization (FISH) for DDIT3 rearrangement, are useful for establishing a correct diagnosis. Although all MLS tumors should have DDIT3 fusions, it is important to be aware of reasons for potential false-negative results. We here present a case of MLS that was negative for FISH for DDIT3, that showed an unexpected t(11;22) at G-banding, but that displayed a characteristic EWSR1::DDIT3 fusion at RNA-sequencing. The results suggest that neoplasia-associated fusions that, due to the transcriptional orientations of the two genes involved, cannot arise through only two double-strand breaks are more likely to be associated with negative FISH-findings and unexpected karyotypes.

Primary lesser sac myxoid liposarcoma: A case report

INTRODUCTION

Lesser sac pathological entities are uncommon. Most of these are tumors and are generally misdiagnosed as retroperitoneal lesions.

CASE REPORT

A 62year old male with past history of treated hypopharyngeal cancer presented with progressive abdominal distension. Physical examination revealed a midline intra abdominal mass in the epigastrium and umbilical region. Radiological investigations were suggestive of a retroperitoneal tumor,an image guided biopsy was reported as atypical lipoma. Surgical exploration confirmed a large multi lobulated tumor arising primarily from the lesser sac, post operative histopathological examination confirmed a myxoid liposarcoma.

DISCUSSION

Primary lesser sac tumors are rare, a literature review of primary lesser sac tumors with particular reference to myxoid liposarcoma is presented.

CONCLUSION

Primary lesser sac liposarcomas are rare neoplasms. The myxoid variant is unique for its peculiar biological behavior, in its sensitivity to chemotherapy and radiotherapy and for the presence of specific cytogenetic marker.

Extensive adipocytic maturation can be seen in myxoid liposarcomas treated with neoadjuvant doxorubicin and ifosfamide and pre-operative radiation therapy

BACKGROUND

Trabectedin and thioglitazones have been documented to induce adipocytic maturation in myxoid liposarcoma; we have noted this in our experience as well. Intriguingly, we have also encountered this same phenomenon in myxoid liposarcomas exposed to various combinations of neoadjuvant doxorubicin and ifosfamide systemic chemotherapy with preoperative radiation, where the pathological effects have been less characterized. We examined the histological changes, including adipocytic maturation, associated with this treatment in patients with myxoid liposarcoma and evaluated for prognostic significance.

METHODS

Twenty-two patients were identified with histologically confirmed myxoid liposarcomas (9 with variable hypercellular areas) who were treated with neoadjuvant doxorubicin (75-90 mg/m2/continous infusion over 72h every 3 week) and ifosfamide (2.5 g/m2 daily x 4 every 3 weeks) for 4-6 cycles. Twenty-one patients received pre-operative radiation including 5 with concurrent gemcitabine. Pre- and post-treatment MRI studies were compared for changes in tumor area, fat content and contrast uptake, with the latter two estimated as: none, <25%, 25-49% and >50%. Post-treatment specimens were evaluated for hyalinization, necrosis and adipocytic maturation. Clinical follow-up was obtained.

RESULTS

Median age was 45 (26-72) years with a median tumor size of 11 (2-18) cm. All occurred in the lower extremities except for one case in the neck. As is common in myxoid liposarcoma, all had extensive treatment changes (>90%) with extensive hyalinization (n = 16; >90%) or prominent adipocytic maturation (n = 6; >50%) including 2 cases composed almost entirely of mature-appearing adipose tissue. Variable necrosis was identified (5-30%). MRI revealed a decrease in tumor area in all but one tumor (median, 65%), an increase in fat content in 7 tumors (n = 2, >50%;n = 2, 25-50%;n = 3,<25%), and a decrease in contrast enhancement in most tumors (n = 5, >50%; n = 9, 25-49%; n = 7, <25%). Median follow-up was 57 (12-96) months with 17 alive with no disease/metastases, 3 alive with disease and 2 dead of disease. Six patients developed metastases with median interval of 26 (22-51) months post resection. Four of 6 tumors with increased adipocytic maturation >50% on histology had increased fat detected by MRI (>25%). All 6 are alive but 2 developed metastases. In the remaining patients, 4 developed metastases with 14 alive and 2 dead of disease.

CONCLUSION

Myxoid liposarcoma exposed to neoadjuvant doxorubicin and ifosfamide and pre-operative radiation can have prominent adipocytic maturation similar to trabectedin treatment. Myxoid liposarcomas exhibit extensive treatment changes with prominent hyalinization being the most common histological change. Despite this, patients develop metastases regardless of adipocytic maturation. While of unclear significance, no patient with fatty maturation died of disease.

Cytogenetics and molecular genetics of myxoid soft-tissue sarcomas

Myxoid soft-tissue sarcomas represent a heterogeneous group of mesenchymal tumors characterized by a predominantly myxoid matrix, including myxoid liposarcoma (MLS), low-grade fibromyxoid sarcoma (LGFMS), extraskeletal myxoid chondrosarcoma (EMC), myxofibrosarcoma, myxoinflammatory fibroblastic sarcoma (MIFS), and myxoid dermatofibrosarcoma protuberans (DFSP). Cytogenetic and molecular genetic analyses have shown that many of these sarcomas are characterized by recurrent chromosomal translocations resulting in highly specific fusion genes (e.g., FUS-DDIT3 in MLS, FUS-CREB3L2 in LGFMS, EWSR1-NR4A3 in EMC, and COL1A1-PDGFB in myxoid DFSP). Moreover, recent molecular analysis has demonstrated a translocation t(1; 10)(p22; q24) resulting in transcriptional upregulation of FGF8 and NPM3 in MIFS. Most recently, the presence of TGFBR3 and MGEA5 rearrangements has been identified in a subset of MIFS. These genetic alterations can be utilized as an adjunct in diagnostically challenging cases. In contrast, most myxofibrosarcomas have complex karyotypes lacking specific genetic alterations. This paper focuses on the cytogenetic and molecular genetic findings of myxoid soft-tissue sarcomas as well as their clinicopathological characteristics.

Contributions of cytogenetics and molecular cytogenetics to the diagnosis of adipocytic tumors

Over the last 20 years, a number of tumor-specific chromosomal translocations and associated fusion genes have been identified for mesenchymal neoplasms including adipocytic tumors. The addition of molecular cytogenetic techniques, especially fluorescence in situ hybridization (FISH), has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal translocations and/or other rearrangements in adipocytic tumors. Indeed, most resent molecular cytogenetic analysis has demonstrated a translocation t(11;16)(q13;p13) that produces a C11orf95-MKL2 fusion gene in chondroid lipoma. Additionally, it is well recognized that supernumerary ring and/or giant rod chromosomes are characteristic for atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma, and amplification of 12q13–15 involving the MDM2, CDK4, and CPM genes is shown by FISH in these tumors. Moreover, myxoid/round cell liposarcoma is characterized by a translocation t(12;16)(q13;p11) that fuses the DDIT3 and FUS genes. This paper provides an overview of the role of conventional cytogenetics and molecular cytogenetics in the diagnosis of adipocytic tumors.

Multiple inflammatory cytokine-productive ThyL-6 cell line established from a patient with thymic carcinoma

Thymic epithelial cells can produce many kinds of cytokines, and interleukin (IL)-6-producing thymic carcinoma cases have been reported. However, a cytokine-producing human thymic tumor cell line has not previously been established. In this paper, we report a novel, multiple inflammatory cytokine-productive cell line that was established from a patient with thymic carcinoma. This cell line, designated ThyL-6, positively expressed epithelial membrane antigen, cytokeratins, vimentin intermediate filament and CD5, although hematological markers were not present in the cells. Cytokine antibody array analysis showed that the cells secreted several cytokines including IL-1alpha, IL-6, IL-8, RANTES, soluble TNFalpha-receptor 1, VEGF and CTLA into the culture medium. The addition of ThyL-6-cultured supernatant supported the growth of human myeloma ILKM-3 cells, which require the presence of IL-6 in the culture medium for the maintenance of cell growth, suggesting that the secreted IL-6 from ThyL-6 cells was biologically active. Chromosome analysis demonstrated that ThyL-6 cells had complex karyotype anomalies, including der(16)t(1;16); the latter has been recognized in thymic squamous cell carcinoma and thymic sarcomatoid carcinoma cases, as well as in several other kinds of malignancies. Heterotransplantation of the cells into nude mice showed tumorigenesis with neutrophil infiltration and liquefactive necrosis. These findings suggest that ThyL-6 cells will provide us with a new experimental tool for investigating not only the pathogenesis, biological behavior, chromo-somal analysis and therapeutic reagents of human thymic carcinoma, but also for studying cytokine-chemokine network systems.

Embryonal rhabdomyosarcoma with a der(16)t(1;16) translocation

Embryonal rhabdomyosarcoma (ERMS) is the most common subtype of RMS that predominantly involves the genitourinary tract and the head and neck regions in children younger than 10 years of age. Cytogenetically, ERMS is most frequently hyperdiploid, with extra copies of chromosomes 2, 7, 8, 11, 12, 13, and 20. No consistent structural chromosomal alteration has been identified in ERMS. In contrast, a t(2;13)(q35;q14) or t(1;13)(q36;q14) corresponding to PAX3-FOXO1A (previously FKHR) and PAX7-FOXO1A gene fusions are considered tumor-specific anomalies for alveolar RMS (ARMS). Occasionally, a recurrent secondary structural rearrangement involving chromosomes 1 and 16 is seen in translocation-positive ARMS, a der(16)t(1;16) resulting in an imbalance of 1q and 16q material. Conventional cytogenetic analysis of an ERMS arising in the urinary bladder of a 22-month-old male child revealed this nonrandom secondary chromosomal aberration, der(16)(1;16)(q22;q24), in a hyperdiploid complement with extra copies of chromosomes 2, 7, 8, 10, 12, 13, 19, and 20. Subsequent analyses showed tumor cells to be negative for FOXO1A, PAX3, or PAX7 gene locus rearrangements (by fluorescence in situ hybridization) and also negative for PAX3-FOXO1A and PAX7-FOXO1A fusion transcripts (by reverse transcriptase-polymerase chain reaction). These results suggest that the unbalanced t(1;16) translocation may be seen in RMSs lacking a primary genetic rearrangement.