Inflammatory malignant fibrous histiocytomas and dedifferentiated liposarcomas: histological review, genomic profile, and MDM2 and CDK4 status favour a single entity

Inflammatory malignant fibrous histiocytoma (inflammatory MFH) is a very rare tumour that occurs most often in the retroperitoneum. So far, it has been considered to be a special subtype of MFH. As it is now widely accepted that most retroperitoneal pleomorphic MFHs are dedifferentiated liposarcomas, the present study compared histological features, genomic profile (CGH analysis), and MDM2 and CDK4 status (immunohistochemistry, FISH, and quantitative PCR) in inflammatory MFHs from 12 patients and dedifferentiated liposarcomas that had an inflammatory MFH component from eight patients. Metaphase cytogenetic and FISH analyses were also performed on one inflammatory MFH. Histological review showed areas of well-differentiated liposarcoma in nine inflammatory MFHs. CGH analysis showed 12q13-15 amplification or gain in six of seven inflammatory MFHs and in seven of seven dedifferentiated liposarcomas. Immunohistochemistry showed positivity of tumour cells for MDM2 in every tumour in both groups and for CDK4 in ten and seven inflammatory MFHs and dedifferentiated liposarcomas, respectively. Metaphase cytogenetic and FISH analysis performed on one inflammatory MFH showed the presence of a supernumerary large marker chromosome and ring chromosome with high-level amplification of both MDM2 and CDK4 genes. FISH analysis on paraffin wax-embedded sections showed amplifications of MDM2 and CDK4 in seven of seven inflammatory MFHs and in seven of seven dedifferentiated liposarcomas. Quantitative PCR showed amplification of MDM2 in six and of CDK4 in seven of nine inflammatory MFHs. In conclusion, this study strongly suggests that most so-called inflammatory MFHs are dedifferentiated liposarcomas.     

Evaluation of MDM2 and CDK4 amplification by real-time PCR on paraffin wax-embedded material: a potential tool for the diagnosis of atypical lipomatous tumours/well-differentiated liposarcomas

Atypical lipomatous tumours/well-differentiated liposarcomas and dedifferentiated liposarcomas are characterized by 12q13-15 region amplification. In contrast, this molecular event has not been reported in benign lipomas. Within the 12q13-15 chromosomal region, the MDM2, SAS, HMGA2, and CDK4 genes are the most frequent targets of amplification. A series of lipomas (36 cases) and liposarcomas (48 cases) was analysed for MDM2 and CDK4 gene amplification by real-time PCR. MDM2 and CDK4 gene amplification was detected in 2.8% and 5.6% of lipomas and 98.2% and 82.4% of liposarcomas, respectively. Moreover, co-amplification of the two genes as well as a higher-level amplification was observed more frequently in dedifferentiated liposarcomas than in atypical lipomatous tumours/well-differentiated liposarcomas. Real-time PCR proved to be a fast and reliable method to characterize lipomas and liposarcomas by quantification of MDM2 and CDK4 gene amplification. It is applicable to paraffin wax-embedded tissues and could be useful when histological diagnosis is difficult.     

The value of MDM2 and CDK4 amplification levels using real-time polymerase chain reaction for the differential diagnosis of liposarcomas and their histologic mimickers

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and dedifferentiated liposarcoma (DDL) are reported to have murine double-minute type 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) amplification as a characteristic genetic alteration. To evaluate the diagnostic utility of this gene abnormality, we analyzed 19 liposarcomas, 21 malignant fibrous histiocytomas, 3 leiomyosarcomas, 5 malignant peripheral nerve sheath tumors, 23 lipomas, and 28 nonneoplastic fat tissues using real-time polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH). In real-time PCR, all ALT/WDLs and DDLs had both MDM2 and CDK4 amplifications. The amplification levels in ALT/WDLs and DDLs were significantly higher than those in the other sarcomas, lipomas, and nonneoplastic fat tissues (P < .05); however, those in the other sarcomas and lipomas were not significantly higher than those in nonneoplastic tissues. In FISH, all ALT/WDLs and DDLs had both MDM2 and CDK4 amplifications, and all of the myxoid/round cell liposarcomas, leiomyosarcomas, malignant peripheral nerve sheath tumors, and all but one of the malignant fibrous histiocytomas did not have the amplifications. In this study, MDM2 and CDK4 amplifications were confirmed in ALT/WDLs and DDLs, and the amplification levels were significantly higher than those in the other tumors. An analysis of MDM2 and CDK4 amplification using real-time PCR, as well as FISH, is useful for the differential diagnosis of liposarcomas and their histologic mimickers.     

Well‐differentiated and dedifferentiated liposarcomas with prominent myxoid stroma: analysis of 56 cases

Aims: Occasional cases of well‐differentiated and dedifferentiated liposarcoma (LPS) contain myxoid stroma, leading to confusion with other sarcomas. The aim of this study was to analyse the clinicopathological and genetic features of well‐differentiated/dedifferentiated LPS with prominent myxoid stroma. Methods and results: Fifty‐six cases of LPS (22 well‐differentiated; 34 dedifferentiated) with prominent myxoid stroma were evaluated. Most arose in the retroperitoneum, abdominal cavity, or spermatic cord. The mean size was 170 mm. Myxoid LPS‐like plexiform vessels were conspicuous in 11 cases of well‐differentiated LPS. In 22 cases of dedifferentiated LPS, myxofibrosarcoma‐like curvilinear vessels were prominent. In other cases, the myxoid component had variably bland or pleomorphic morphology. By immunohistochemistry, staining for MDM2 was positive in 95% of cases, and CDK4 in 78%. Cytogenetics in 13 cases showed ring and giant marker chromosomes. Fluorescence in‐situ hybridization showed amplification of 12q13–15 in six cases evaluated. Of 30 patients with follow‐up, all but one had local recurrences (up to four), but only one has so far had distant metastases. Conclusions: Well‐differentiated/dedifferentiated LPS with prominent myxoid stroma can closely resemble other sarcoma types, especially myxoid LPS and myxofibrosarcoma. The clinical presentation (large retroperitoneal or abdominal tumour) is a clue to the correct diagnosis; the degree of nuclear atypia helps to exclude myxoid LPS. Immunohistochemistry for MDM2 and CDK4 and genetic analysis can be useful to confirm the diagnosis.     

Retroperitoneal dedifferentiated liposarcoma lacking MDM2 amplification in a patient with a germ line CHEK2 mutation

Germ line mutations in genes that encode proteins involved in the DNA damage response predispose patients to a variety of tumors. Checkpoint kinase 2, encoded by the CHEK2 gene, is important in transducing the DNA damage response. Germ line CHEK2 mutations are seen in a subset of patients with a familial breast cancer and sarcoma phenotype. We report a case of retroperitoneal dedifferentiated liposarcoma in a 61-year-old female with germ line CHEK2 mutation. MDM2 gene amplification normally present and used to aid in the diagnosis of retroperitoneal dedifferentiated liposarcoma was absent in this case. Lack of MDM2 overexpression has similarly been reported in liposarcomas arising in patients with germ line TP53 mutations. We propose this case may highlight a nonamplified MDM2 phenotype in well- and dedifferentiated liposarcomas arising in patients with germ line mutations of genes involved in p53-associated DNA damage response pathways.     

The CDKN2A/CDKN2B/CDK4/CCND1 pathway is pivotal in well-differentiated and dedifferentiated liposarcoma oncogenesis: an analysis of 104 tumors

The MDM2 and CDK4 genes are the main targets of chromosome 12 amplification in well-differentiated and dedifferentiated liposarcomas. Nevertheless, around 10% of these tumors do not amplify CDK4. To find substitutive alterations of CDK4 amplification, we analyzed a large series of liposarcomas by array-CGH, real-time genomic PCR, gene expression array, and real-time RT-PCR. We demonstrate that an alteration in the CDKN2A/CDKN2B/CDK4/CCND1 pathway is present in almost all cases without CDK4 amplification, thereby confirming the pivotal role of this pathway in liposarcoma oncogenesis. Moreover, we show that cell cycle and differentiation are driven by a subtle and complex balance between members of this pathway. Finally, we demonstrate that in tumors without amplification/overexpression of CDK4, the chromosome 1q21-1q23 region is a preferential partner of chromosome 12 amplicon, suggesting that the mechanism of amplification is slightly different in this group of tumors.     

Mixed-type liposarcoma: clinicopathological, immunohistochemical, and molecular analysis of a case arising in deep soft tissues of the lower extremity

A rare case of mixed-type liposarcoma arising in deep soft tissue of the right thigh of a 45-year-old female patient is reported. The neoplasm was completely excised and was composed of an irregular admixture of areas of atypical lipomatous tumor/well-differentiated liposarcoma of the lipoma-like subtype with areas of myxoid/round cell liposarcoma. An amplification of the MDM2 and CDK4 genes respectively in the atypical lipomatous tumor/well-differentiated liposarcoma areas was detected by fluorescence in situ hybridization (FISH) analysis, and translocations of the CHOP and FUS genes were detected by FISH analysis in the myxoid/round cell liposarcoma areas.     

Sensitivity of MDM2 amplification and unexpected multiple faint alphoid 12 (alpha 12 satellite sequences) signals in atypical lipomatous tumor

This study assessed whether analysis of MDM2 copy number by fluorescence in situ hybridization (FISH) would help distinguish lipomas from atypical lipomatous tumors, otherwise referred to as well-differentiated liposarcomas, using a commercially available MDM2 FISH kit. 227 lipomatous and 201 non-lipomatous tumors were analyzed to assess its sensitivity and specificity. Of 178 mature lipomatous tumors, 86 were classified histologically as lipoma and 92 as atypical lipomatous tumor. Two of the lipomas harboring MDM2 amplification were reclassified as atypical lipomatous tumors. Overall, 13 atypical lipomatous tumors did not reveal MDM2 or CDK4 amplification, although this was reduced to 12 following analysis of multiple slides. Three of these cases revealed very occasional tumor cells harboring high-level MDM2 amplification, two had a dedifferentiated component, and MDM2 amplification was detected when one tumor recurred. The remaining six cases exhibited reactive/inflammatory features and were reclassified as lipomas. The findings indicate that MDM2 amplification is 93.5% sensitive for diagnosing atypical lipomatous tumor. A total of 2 of the 20 dedifferentiated liposarcomas failed to reveal MDM2 amplification. All atypical lipomatous tumors measured >10?cm, two dedifferentiated liposarcoma presented de novo at <10?cm, and ～50% of lipomas measured >10?cm. Spindle cell lipomas, lipoblastomas, hibernomas and pleomorphic liposarcomas did not reveal MDM2 amplification. Of 201 non-lipomatous tumors, eight revealed MDM2 amplification or multiple faint alphoid 12 signals and were reclassified as dedifferentiated liposarcoma. Multiple faint alphoid 12 signals were observed in nine tumors from seven patients, an observation not previously reported on paraffin sections: these included four atypical lipomatous tumors, and three dedifferentiated liposarcomas, one previously diagnosed as a myxofibrosarcoma, all of which also revealed amplification of CDK4, although two lacked MDM2 amplification. MDM2 FISH test is a useful adjunct to histology for distinguishing lipoma from atypical lipomatous tumor. The limitations of molecular genetic tests must be known before introducing them into a clinical service.     

Gains of 13q are correlated with a poor prognosis in liposarcoma.

Liposarcomas are a phenotypical heterogeneous group of tumors divided into four main subtypes: well-differentiated, dedifferentiated, myxoid/round cell, and pleomorphic. The aim of this study was to compare DNA sequence copy number changes of these subtypes as investigated by comparative genomic hybridization in 36 patients. Comparative genomic hybridization revealed genomic imbalances in tumors of 27 patients (mean 5.6 imbalances per tumor). The most frequent gains were within single regions of 1q, 12q, and 13q. We found a significant correlation of poor overall survival and gain of 13q21 (P=0.0221), 13q22 (P=0.0341), 13q31 (P=0.0410), and 13q32 (P=0.0074). The univariate Cox regression analysis revealed an increased risk of tumor-related death for patients whose liposarcomas possess with gains of 13q21 and 13q32 simultaneously (P=0.010; RR=7.1; 95% CI 1.6-31.7). Furthermore, 12 high-level amplifications were found in tumors of seven patients. In four cases 12q14-q15 and in two cases 13q32-q33 were amplified. We identified in different liposarcoma subtypes characteristic genomic changes: Gains and high-level amplifications of 12q occurred in all 11 investigated well-differentiated liposarcomas, and these changes were often present simultaneously with gains of 1q (mean 5.5 changes). In the two dedifferentiated liposarcomas, gains of 1q in both liposarcomas, and a high-level amplification of 13q were striking. Only eight of the 17 patients with myxoid/round cell liposarcomas showed changes in DNA copy number (mean 3.4 imbalances). In four of these eight cases gains of 13q occurred. The six pleomorphic liposarcomas possessed the most frequent genomic imbalances (mean number 16.3) of all liposarcoma subtypes investigated. These imbalances were in almost all chromosomal regions detected predominantly as over-representations of chromosomes 1, 5p, 13q, and 22q. Summarizing, all subtypes but well-differentiated liposarcomas showed gains of 13q, which were associated with a poor prognosis.     

Dedifferentiated myxoid liposarcoma: a clinicopathological study suggesting a closer relationship between myxoid and well-differentiated liposarcoma

Myxoid/round cell liposarcoma is arguably the commonest type of liposarcoma occurring in the extremities and may show gradual progression from low-grade, pure myxoid liposarcoma to high-grade round cell liposarcoma. Rarely myxoid/round cell liposarcoma is associated with areas of well-differentiated or pleomorphic liposarcoma (mixed liposarcoma). We describe the clinicopathological features of three unusual myxoid/round cell liposarcomas which showed morphological features of de novo dedifferentiation. All patients were male and were aged 66, 70 and 76 years, respectively. One lesion each arose in the retroperitoneum, inguinal region and peritoneal cavity. Histologically, in one case the myxoid/round cell component was juxtaposed to a high-grade non-lipogenic component resembling non-pleomorphic storiform 'malignant fibrous histiocytoma' ('MFH'), one case showed a combination of myxoid liposarcoma and a high-grade myxofibrosarcoma-like component (so-called myxoid 'MFH'), and in the third case, a well-differentiated myxoid liposarcoma with a discontinuous micronodular pattern of dedifferentiation was seen. Follow-up information of 30, 28 and 26 months revealed two recurrences each in two patients. These patients died of postoperative pulmonary embolism and abdominal haemorrhage, respectively; systemic metastases were not noted. These cases demonstrate that myxoid/round cell liposarcoma can show, albeit very rarely, histological features of dedifferentiation. Cases like these, combined with the occurrence of mixed-type liposarcoma (well-differentiated/myxoid liposarcoma) and the vicinity of chromosomal regions involved by specific karyotypic aberrations in these tumours, suggest that myxoid/round cell liposarcoma and well-differentiated liposarcoma (including its dedifferentiated variant) are more closely related in biological terms than is generally believed.     

Molecular updates in adipocytic neoplasms✰

Adipocytic neoplasms include a diversity of both benign tumors (lipomas) and malignancies (liposarcomas), and each tumor type is characterized by its own unique molecular alterations driving tumorigenesis. Work over the past 30 years has established the diagnostic utility of several of these characteristic molecular alterations (e.g. MDM2 amplification in well- and dedifferentiated liposarcoma, FUS/EWSR1-DDIT3 gene fusions in myxoid liposarcoma, RB1 loss in spindle cell/pleomorphic lipoma). More recent studies have focused on additional molecular alterations which may have therapeutic or prognostic impact. This review will summarize several of the important molecular findings in adipocytic tumors that have been described over the past 10 years.     

Retroperitoneal dedifferentiated liposarcoma with osteosarcomatous components: a case report

We report a rare case of recurrent retroperitoneal dedifferentiated liposarcoma with osteosarcomatous components. An 82-year-old male diagnosed with recurrent retroperitoneal liposarcoma underwent a tumor resection. Histologically, osseous matrix with osteoid and mature hyaline cartilaginous tissues with high cellularity were observed in a fibrous background through most of the tumor, and scattered MDM2- and CDK4-positive atypical hyperchromatic stromal cells were detected surrounding the dedifferentiated areas. Dedifferentiation occurs in up to 10% of well-differentiated liposarcomas, frequently resembling a malignant fibrous histiocytoma-like pleomorphic sarcoma. In contrast, divergent differentiation with osteosarcomatous components is considered to be extremely rare.     

Dedifferentiation of a well-differentiated liposarcoma to a highly malignant metastatic osteosarcoma: amplification of 12q14 at all stages and gain of 1q22-q24 associated with metastases

Well-differentiated liposarcomas (WDLPS), especially those located in the retroperitoneum, may occasionally undergo dedifferentiation. Although this process is associated with a more aggressive clinical course, dedifferentiated liposarcomas rarely produces metastases. The case reported here is rather uncommon: A retroperitoneal WDLPS gave lung metastases that were diagnosed as highly malignant osteosarcomas. We used comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH), and Southern blot analyses to characterize the copy number changes and genetic aberrations occurring at different stages of the disease. In the primary tumor, the only detectable aberration was amplification of 12q13-q14, which was present only in a fraction of the cells and revealed by FISH analysis. High-level amplification of 12q13-q14, involving CDK4, MDM2, and HMGIC, was seen both in the relapse and the metastases. The second most common change, gain or high-level amplification of 1q22-q24, was detectable by CGH only in the osteogenic metastases, as was loss of the distal 2q. FISH analyses revealed considerable heterogeneity in the samples, and the percentage of cells showing aberrations was significantly higher in the metastatic samples. In particular, increased copy numbers of 789f2, a marker for 1q21 amplification in sarcomas, was observed in more than 65% of the cells in the metastatic samples, but in less than 10% of the cells from the recurrent samples. These observations could indicate that 1q amplification, in particular, may be indicative of a more malignant phenotype and ability of metastasis in WDLPS, as has also been suggested by others.     

Well-differentiated liposarcoma and dedifferentiated liposarcoma: An updated review

Well-differentiated liposarcoma (WDL)/atypical lipomatous tumor and dedifferentiated liposarcoma (DDL) together comprise the largest subgroup of liposarcomas, and constitute a histologic and behavioral spectrum of one disease. WDL and DDL typically occur in middle-aged to older adults, particularly within the retroperitoneum or extremities. WDL closely resembles mature adipose tissue, but typically shows fibrous septation with variable nuclear atypia and enlargement. WDL does not metastasize, but can dedifferentiate to DDL, which is associated with more aggressive clinical behavior, with a greater propensity for local recurrence and the capacity for metastasis. Although distant metastasis is rarer in DDL compared with other pleomorphic sarcomas, behavior is related to location, with a significantly worse outcome in retroperitoneal tumors. DDL typically has the appearance of undifferentiated pleomorphic or spindle cell sarcoma, and is usually a non-lipogenic sarcoma that is adjacent to WDL, occurs as a recurrence of WDL or which can arise de novo. WDL and DDL share similar background genetic aberrations; both are associated with high-level amplifications in the chromosomal 12q13-15 region, which includes the CDK4 and MDM2 cell cycle oncogenes. In addition, DDL harbor further genetic changes, particularly 6q23 and 1p32 coamplifications. While surgical excision remains the treatment mainstay with limited medical options for patients with aggressive recurrent disease or metastases, novel targeted therapies towards the gene products of chromosome 12 are being evaluated. This review summarizes the pathology of WDL and DDL, discussing morphology, immunohistochemistry, genetics and the differential diagnosis.     

Focal rhabdomyosarcomatous differentiation in primary liposarcoma.

A unique case of primary myxoid liposarcoma of the thigh, in which focal pleomorphic areas were present containing rhabdomyoblasts, is described. Focal rhabdomyosarcoma in liposarcoma has only rarely been reported previously and only in dedifferentiated liposarcomas of the retroperitoneum. All but one have been recurrences with rhabdomyoblasts being absent in the primary liposarcoma. As rhabdomyoblasts were only focally present, the present case is regarded as liposarcoma with focal divergent rhabdomyoblastic differentiation rather than malignant mesenchymoma.     

Cytogenetic and molecular genetic analyses of liposarcoma and its soft tissue simulators: recognition of new variants and differential diagnosis

Liposarcoma is one of the most common sarcomas of adults. Its differential diagnosis and accurate subclassification are often problematic; the latter is also important with regard to appropriate treatment and prognosis. We studied a series of 23 liposarcomas that had unusual or previously undescribed features and 10 liposarcoma simulators and correlated the morphologic, cytogenetic, and molecular genetic findings. We found that use of cytogenetic-molecular genetic techniques aids in the distinction between myxoid-round cell liposarcoma and their simulators, chondroid lipoma, myxoid spindle cell-pleomorphic lipoma, cellular intramuscular myxoma, and myxofibrosarcoma. Poorly differentiated forms of round cell liposarcoma lacking morphologic evidence of lipogenesis can also be diagnosed using these techniques; however, the techniques do not aid in distinguishing low-grade myxoid from high-grade round cell liposarcomas. This study also shows that retroperitoneal liposarcomas with myxoid liposarcoma-like zones are part of the morphologic spectrum of well-differentiated-dedifferentiated liposarcoma rather than true myxoid liposarcomas. Perhaps most importantly, our results provide the first molecular genetic evidence that true mixed liposarcomas (mixed well-differentiated and myxoid liposarcoma) do indeed exist. They also unequivocally demonstrate the existence of small, round cell variants of pleomorphic liposarcoma that closely simulate myxoid-round cell liposarcoma.     

伴有脑膜上皮细胞样旋涡状特征的去分化脂肪肉瘤六例临床病理学观察

目的探讨伴有脑膜上皮细胞样旋涡特征的去分化脂肪肉瘤(dedifferentiated liposarcomas with meningothelial-like whorls,DDLMW)的组织形态学、免疫组织化学及分子遗传学特征。方法收集江苏省人民医院(南京医科大学第一附属医院)2012年3月至2018年8月诊断为DDLMW的患者6例病历资料及存档切片,采用免疫组织化学染色检测MDM2、CDK4、p16等,应用荧光原位杂交(FISH)法检测MDM2基因扩增情况,并复习相关文献。结果患者男性3例,女性3例;4例发生于后腹膜,2例发生于纵隔,发病年龄范围40~77岁(中位年龄58岁)。大体表现为巨大单发或多发结节状肿块,镜下除了可见高分化脂肪肉瘤成分之外,均可见具有特征性的旋涡样结构,形态类似脑膜瘤;旋涡小体肿瘤细胞梭形或卵圆形,同心圆状致密排列,轻-中度异型性;此外,4例在旋涡小体的周围或中间可见化生性骨组织。免疫表型:肿瘤组织表达MDM2、CDK4、p16,不表达S-100蛋白、平滑肌肌动蛋白、SOX10、上皮细胞膜抗原、CD21、CD23、CD35;肿瘤细胞Ki-67阳性指数低。6例经FISH检测均显示肿瘤细胞伴有MDM2基因的扩增。结论DDLMW是一种罕见的去分化脂肪肉瘤的组织学亚型,特征性的旋涡状结构并不预示其有神经束膜或滤泡树突细胞的分化,认识并熟悉其存在结合免疫组织化学及MDM2基因FISH检测有助于其诊断与鉴别诊断。