Retroperitoneal liposarcoma with combined well-differentiated and myxoid malignant fibrous histiocytoma-like myxoid areas

Myxoid Pleomorphic Liposarcoma

Myxoid pleomorphic liposarcoma (MPLPS) shows a strong predilection for the mediastinum and can affect a wide age range. Clinically, MPLPS exhibits aggressive behavior and demonstrates a worse overall and progression-free survival than myxoid/round cell liposarcoma (MRLPS) and pleomorphic liposarcoma (PLPS). Histologically, MPLPS is characterized by hybrid morphologic features of MRLPS and PLPS, including myxoid stroma, chicken wire-like vasculature, univacuolated and multivacuolated lipoblasts, and high-grade pleomorphic sarcomatous components. In terms of molecular features, MPLPS is distinct from other lipomatous tumors as it harbors genome-wide loss of heterozygosity.

Undifferentiated and dedifferentiated soft tissue neoplasms: Immunohistochemical surrogates for differential diagnosis

Undifferentiated soft tissue sarcomas (USTS) are described in the current World Health Organization Classification of Soft Tissue and Bone Tumours as those showing no identifiable line of differentiation when analyzed by presently available technologies. This is a markedly heterogeneous group, and the diagnosis of USTS remains one of exclusion. USTS can be divided into four morphologic subgroups: pleomorphic, spindle cell, round cell and epithelioid undifferentiated sarcomas, with this combined group accounting for up to 20% of all soft tissue sarcomas. As molecular advances enable the stratification of emerging genetic subsets within USTS, particularly within undifferentiated round cell sarcomas, other groups, particularly the category of undifferentiated pleomorphic sarcomas (UPS), still remain difficult to substratify and represent heterogeneous collections of neoplasms often representing the common morphologic endpoints of a variety of malignant tumors of various (mesenchymal and non-mesenchymal) lineages. However, recent molecular developments have also enabled the identification and correct classification of many tumors from various lines of differentiation that would previously have been bracketed under 'UPS'. This includes pleomorphic neoplasms and dedifferentiated neoplasms (the latter typically manifesting with an undifferentiated pleomorphic morphology) of mesenchymal (e.g. solitary fibrous tumor and gastrointestinal stromal tumor) and non-mesenchymal (e.g. melanoma and carcinoma) origin. The precise categorization of 'pleomorphic' or 'undifferentiated' neoplasms is critical for prognostication, as, for example, dedifferentiated liposarcoma typically behaves less aggressively than other pleomorphic sarcomas, and for management, including the potential for targeted therapies based on underlying recurrent molecular features. In this review we focus on undifferentiated and dedifferentiated pleomorphic and spindle cell neoplasms, summarizing their key genetic, morphologic and immunophenotypic features in the routine diagnostic setting, and the use of immunohistochemistry in their principal differential diagnosis, and highlight new developments and entities in the group of undifferentiated and dedifferentiated soft tissue sarcomas.

[Retroperitoneal dedifferentiated liposarcomas: semi-quantitative assessment of the dedifferentiated component and prognosis]

OBJECTIVE

To evaluate the impact of malignancy grade and the proportion of the dedifferentiated component (DC) in retroperitoneal dedifferentiated liposarcomas (DDLS) on the course and prognosis of the disease.

MATERIAL AND METHODS

The retrospective study enrolled 74 patients with primary retroperitoneal DDLS who underwent radical surgical treatment in the N.N. Blokhin National Medical Research Center of Oncology, Ministry of Health of Russia. Histological surgery specimens from all cases of DDLS were reexamined and reclassified. According to malignancy grades and the proportion of the dedifferentiated component in the tumor, the patients were divided into the comparison groups included in the intergroup analysis of overall and relapse-free survival (OS and RFS) rates. The authors also analyzed the relationship between the proportion of the dedifferentiated component in DDLS and the frequency of adjacent organ invasion.

RESULTS

Patients with a more than 15% dedifferentiated component had significantly lower OS rates than those with a less than 15% one (p=0.0001; log-rank test). The median OS in the DDLS group with a less than 15% dedifferentiated component was 91 months (95% CI, 82-100); that in the DDLS group with a more than 15% dedifferentiated component was 29 months (95% CI 17-41). The 5-year overall survival rates in the groups with less than 15% and more than 15% dedifferentiated components were 69% and 2%, respectively. The group with a more than 15% dedifferentiated component had significantly lower RFS rates than that with a less than 15% one (p=0.0001; log-rank test). In the DDLS groups with less than 15% and more than 15% dedifferentiated components, the median RFS rates were 25 months (95% CI 23-27) and 13 months (95% CI 8-18), respectively. In these groups, the 2-year RFS rates were equal to 50% and 9%, respectively. In the DDLS groups with less than 15% and more than 15% dedifferentiated components, pathologically confirmed invasion into the adjacent organs was observed in 32% and 63% of cases, respectively. There were no statistically significant differences in the OS and RFS of patients with DDLS according to tumor grade (p=0.069; p=0.102).

CONCLUSION

This investigation suggests that DDLS have a more aggressive course with an increasing proportion of the dedifferentiated component in the tumor. Considering the histological variability in the dedifferentiated component, which is demonstrated in the research and scientific literature, as well as lack of a prognostic impact of histological grade, the authors believe that semi-quantitative assessment of the proportion of the dedifferentiated component in DDLS is able to serve as a simple and efficient morphological marker for the course of the disease and prognosis in retroperitoneal DDLS.

Comparative Study of Myxofibrosarcoma With Undifferentiated Pleomorphic Sarcoma: Histopathologic and Clinicopathologic Review

Myxofibrosarcoma (MFS) is a malignant fibroblastic/myofibroblastic neoplasm with the prominent myxoid area. It has the clinical features of frequent local recurrence and occasional distant metastasis. Morphologically, MFS is occasionally difficult to distinguish from undifferentiated pleomorphic sarcoma (UPS), especially in the case of high-grade MFS. Here, we reviewed clinical and histologic data of 162 MFS cases and 43 UPS cases. MFS was distinguished from UPS with the criterion of 10% myxoid area as a cutoff value. Overall, 52 MFS (34.4%) and 9 UPS (20.9%) cases showed local recurrence, 18 MFS (12.2%) and 19 UPS (44.2%) cases developed distant metastasis, and 13 MFS (9.5%) and 14 UPS (32.6%) cases resulted in tumor-related death. Statistically, MFS had a better prognosis than UPS. Moreover, MFS with less myxoid area had a tendency to present a poorer prognosis. FNCLCC grade was a statistically significant prognostic factor (distant metastasis: P=0.0021, tumor-related death: P=0.0021). Cellularity and nuclear atypia had only a statistical tendency for associations with a poorer prognosis. The overall survival rate of MFS after transformation into a UPS-like condition (<10% myxoid area) was close to that of UPS. It was suggested that MFS is a biologically distinct tumor from UPS, and MFS with less myxoid area had a tendency to present a poorer prognosis. We considered that evaluation of the amount of myxoid area, cellularity, and nuclear atypia may be important as prognostic predictors. MFS may become similar to histologic malignancy of UPS in terms of morphology and biology via local recurrence.

Dedifferentiated Liposarcoma With Myofibroblastic Differentiation

CONTEXT.—

Liposarcoma is divided into myxoid, pleomorphic, well-differentiated, and dedifferentiated subtypes. Dedifferentiated liposarcoma displays the greatest histomorphologic diversity, including a subset with myofibroblastic differentiation that shares similarities with a spectrum of reactive, benign, and malignant soft tissue lesions. Misdiagnosis may lead to deleterious consequences, as dedifferentiated liposarcoma differs significantly in its prognosis and treatment from its mimics.

OBJECTIVE.—

To review the clinicopathologic, immunohistochemical, and molecular features of the myofibroblastic variant of dedifferentiated liposarcoma as well as the key distinguishing features from its mimics.

DATA SOURCES.—

Review of pertinent literature on major features and current understanding of dedifferentiated liposarcoma with myofibroblastic differentiation.

CONCLUSIONS.—

The myofibroblastic variant of dedifferentiated liposarcoma is an uncommon and underrecognized sarcoma with several important differential diagnoses, and likely represents the major subset of aggressive retroperitoneal tumors that may have been misdiagnosed as desmoid-type fibromatosis, inflammatory myofibroblastic tumor, or another type of sarcoma in the past.

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.

Myxofibrosarcoma primary cultures: molecular and pharmacological profile

Background:

Myxofibrosarcoma (MFS), formerly considered as a myxoid variant of malignant fibrous histiocytoma, is the most common sarcoma of the extremities in adults and is characterized by a high frequency of local recurrence. The clinical behavior of MFS is unpredictable and the efficacy of chemotherapy is still not well documented. Furthermore, given the relatively recent recognition of MFS as a distinct pathologic entity its cellular and molecular biology has still not been extensively studied in patient-derived preclinical models. We examined the molecular biology and treatment outcomes of high-grade, patient-derived MFS primary cultures.

Methods:

A total of three patient-derived MFS primary cultures were analyzed. We evaluated the role of CD109 expression and also looked for a correlation between transforming growth factor-beta (TGF-β) expression and sensitivity of the primary cultures to different drugs.

Results:

CD109 was a promising marker for the identification of more aggressive high-grade MFS and a potential therapeutic target. The results also highlighted the potential role of TGF-β in chemoresistance. Pharmacological analysis confirmed the sensitivity of the cultures to chemotherapy. The most active treatments were epirubicin alone and epirubicin in combination with ifosfamide, the latter representing the current standard of care for soft tissue sarcomas (STSs), including MFS.

Conclusions:

Our results provide a starting point for further research aimed at improving the management of MFS patients undergoing chemotherapy.

Activity of anthracycline- and ifosfamide-based chemotherapy in a series of patients affected by advanced myxofibrosarcoma

BACKGROUND

We report on the activity of anthracycline-based and high-dose prolonged-infusion ifosfamide chemotherapy in a retrospective series of patients affected by advanced myxofibrosarcoma treated at Istituto Nazionale Tumori in Milan, Italy, and within the Italian Rare Cancer Network (RTR).

METHODS

Advanced myxofibrosarcoma patients treated with anthracycline + ifosfamide and high-dose prolonged-infusion ifosfamide as a single agent from November 2001 to December 2016 were retrospectively reviewed. All pathological diagnosis were centrally reviewed by at least two expert pathologists. Response was evaluated by RECIST, and survival functions were computed.

RESULTS

Among 34 advanced myxofibrosarcoma patients, 13 were treated with front-line anthracycline + ifosfamide chemotherapy (male/female = 6/7, median age 54 years, range 33-72). Overall best response was: 4 partial responses, 3 stable diseases and 6 progressive diseases, with a median progression-free survival of 4 months. Twenty-eight patients received second/further line high-dose prolonged-infusion ifosfamide (male/female = 17/11, median age 55 years, range 27-75 years). We observed 10 partial responses, 4 stable diseases and 14 progressive diseases, with a median progression-free survival of 4 months. Median overall survival was 12 months.

CONCLUSIONS

This retrospective analysis suggests that the combination of anthracyclines and ifosfamide is active in myxofibrosarcoma. In patients already treated with a combination of anthracyclines and ifosfamide, high-dose prolonged-infusion ifosfamide showed activity as well.

Dedifferentiated Liposarcoma: Updates on Morphology, Genetics, and Therapeutic Strategies

Well-differentiated liposarcoma (WDL) and dedifferentiated liposarcoma (DDL) form the largest subgroup of liposarcomas, and represent a morphologic and behavioral spectrum of 1 disease entity, which arises typically in middle to late adult life, most frequently within the retroperitoneum or extremities. DDL is defined as nonlipogenic sarcoma that is juxtaposed to WDL, occurs as a recurrence of WDL or which can arise de novo, and typically has the appearance of undifferentiated pleomorphic or spindle cell sarcoma. DDL have a propensity for local recurrence, whereas distant metastasis is rarer, and behavior is related to anatomic site, with retroperitoneal neoplasms showing a significantly worse prognosis. Surgical resection remains the mainstay of treatment, and medical options for patients with aggressive recurrent or metastatic disease are limited. DDL share similar genetic abnormalities to WDL, with high-level amplifications of chromosome 12q14-15, including the MDM2 and CDK4 cell cycle oncogenes, and DDL harbor additional genetic changes, particularly coamplifications of 6q23 and 1p32. Novel therapies targeted at the gene products of chromosome 12 are being tested in clinical trials. We review the pathology and genetics of DDL, discussing morphologic patterns, immunohistochemical and genetic findings, the differential diagnosis, and future therapeutic strategies.

Association of FPGS genetic polymorphisms with primary retroperitoneal liposarcoma

Primary retroperitoneal liposarcoma is generally regarded as a genetic disorder. We have retrospectively genotyped 8 single nucleotide polymorphisms (SNPs) in 6 candidate genes (MDM2, CDK4, CDC27, FPGS, IGFN1, and PRAMEF13) in 138 patients and 131 healthy control subjects to evaluate the effects of genetic factors on individual susceptibility to primary retroperitoneal liposarcoma in Chinese population. Three SNPs (rs2870820, rs1695147, rs3730536) of MDM2 showed significant differences in single-loci genotypes and allele frequencies between case and control groups (p < 0.05). The minor allele G of SNP rs10760502 in FPGS (folylpolyglutamate synthase) gene was significantly associated with increased risk for primary retroperitoneal liposarcoma, compared with major allele A. Our data suggest that FPGS variant in Chinese population may affect individual susceptibility to primary retroperitoneal liposarcoma.

Extensive lipoma-like changes of myxoid liposarcoma: morphologic, immunohistochemical, and molecular cytogenetic analyses

Myxoid liposarcomas (MLSs) with extensive lipoma-like changes (MLSLC) are rare, and it is often difficult to distinguish them from well-differentiated liposarcoma (LS)/dedifferentiated LS (WDLS/DDLS) with myxoid changes. For the characterization of these neoplasms, we studied 8 MLSLCs, 11 ordinary MLSs, 4 WDLSs, and 6 DDLSs. Cytogenetically, MLSLC and ordinary MLS were characterized by t(12;16)(q13;p11) and FUS-DDIT3 fusion gene, whereas WDLS/DDLS lacked the fusion gene but possessed giant marker/ring chromosomes. Both lipoma-like and myxoid components of the same MLSLC exhibited the identical FUS-DDIT3, as confirmed by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemically, MDM2 and CDK4 were positive in WDLS/DDLS but negative in MLSLC and ordinary MLS. PPARγ, C/EBPα, adipophilin, and perilipin were found in each type of LS. Adipophilin was expressed chiefly in tiny fat droplets of immature lipoblasts, whereas perilipin showed a strong positive staining in large fat vacuoles of signet ring and multivacuolated lipoblasts. The Ki-67 labeling index was lower in the lipoma-like component of MLSLC when compared with the myxoid component of the same tumors as well as ordinary MLS (p < 0.001). When compared with ordinary MLS, MLSLC may be less aggressive in clinical behavior (rare recurrences or metastases) after a wide surgical excision. In conclusion, the distinction between MLSLC and WDLS/DDLS is important, because of the differences of molecular cytogenetic features as well as clinical behaviors between these distinct sarcomas presenting similar morphologic features. In addition, the combined immunohistochemical detection of adipophilin and perilipin may provide a useful ancillary tool for identification of lipoblastic cells in soft tissue sarcomas.

Recurrent giant liposarcoma of the spermatic cord

A giant recurrent retroperitoneal liposarcoma of the spermatic cord was removed in a 40-year-old man. The tumor measured 50 cm and weighed 42 Kilograms. Radiotherapy and chemotherapy have little role in this neoplasm. Despite the huge dimension of the mass surgery was successfully undertaken without relapse at 12 months follow-up.

Myxofibrosarcoma: prognostic factors and survival in a series of patients treated at a single institution

BACKGROUND

First described in 1977, myxofibrosarcoma is one of the most common sarcoma subtypes of the elderly. Until some years ago, myxofibrosarcoma was diagnosed as "myxoid malignant fibrous histiocytoma." The aim of this retrospective case series analysis was to investigate prognostic factors and the clinical outcome of a cohort of patients with myxofibrosarcoma treated at a single institution.

METHODS

We reviewed 158 patients with localized myxofibrosarcoma who underwent surgery at the Istituto Nazionale Tumori of Milan, Italy, over 15 years. Local recurrence, distant metastases, and survival were analyzed.

RESULTS

One hundred twenty patients had primary tumors, while 38 patients had locally recurrent tumors. Five-year overall survival was 77%. Tumor size, grade, and margins were statistically significant predictors of survival. Five-year local recurrence and distant metastases rate were 18% and 15%, respectively. Surgical margins were the only statistically significant prognosticator of local relapses. Patients treated with radiotherapy had the same prognosis as nontreated patients, but likely they had worse local presentations. The histological grade correlated with distant recurrences but not with local relapses. The value of adjuvant chemotherapy could not be determined.

CONCLUSIONS

Patients with myxofibrosarcoma have a better disease-specific survival than other sarcoma subtypes, but also a higher local relapse rate. This is likely related to the peculiar local growth pattern of these tumors. Adequate surgery should be pursued, while the role of adjuvant therapies need to be investigated.

Analysis of CHOP rearrangement in pleomorphic liposarcomas using fluorescence in situ hybridization

Pleomorphic liposarcoma (PLS) is an aggressive subtype of liposarcoma composed of high-grade sarcoma with pleomorphic lipoblasts. PLS usually exhibits a heterogeneous histology and sometimes has a myxoid or round cell area similar to myxoid/round cell liposarcomas (MLS/RCs). Using fluorescence in situ hybridization (FISH) analysis, we investigated the existence of CHOP split signals in various histological areas of PLS including the MLS/RC-like feature and also estimated the distribution of various signals with polyploidy and amplification. Moreover, to detect CHOP fusion transcripts we performed nested reverse transcription-polymerase chain reaction (RT-PCR). Seven PLSs and three MLS/RCs were selected for FISH analysis using the locus-specific indicator CHOP (12q13) dual color, break apart probe (Vysis, USA). The FISH analysis was applied to formalin-fixed, paraffin-embedded tissue sections of representative areas in all cases. Six of seven PLS cases showed the CHOP split signal ranging from 0.5% to 3% of counted nuclei, while all cases of MLS/RC exhibited CHOP rearrangement in more than 50% of counted nuclei. All cases of PLS showed a varied distribution of extra signals with polyploidy and amplification in each histological area. No CHOP fusion transcript was found in any case of PLS by nested RT-PCR. A CHOP rearrangement in PLS should be recognized only as a representative part of complex karyotypes, because the number of cells with split signals was minute compared with that of MLS/RC, and the signals were found in any area despite their histological differences. The cytogenetic background of PLS and that of MLS/RC are obviously different despite histological similarity.

Atypical Lipomatous Tumor, its Variants, and its Combined Forms

Sixty-one cases of neoplasms composed wholly or in part of atypical lipomatous tumor were reviewed. Minimum follow-up was 10 years. The cases were divided into 4 groups based on the findings in the initial excision specimen: conventional atypical lipomatous tumor (n=15), cellular atypical lipomatous tumor (n=21), dedifferentiated liposarcoma (n=24), and atypical lipomatous tumor with a pleomorphic liposarcoma-like component (n=1). The term "cellular atypical lipomatous tumor" was applied to atypical lipomatous tumors having areas of increased cellularity that when non-lipogenic lacked the 5 mitotic figures per 10 high-power fields (maximal rate) required for a dedifferentiated component and when lipogenic fell short of being truly pleomorphic liposarcoma-like. Myxoid regions within this spectrum sometimes had prominent or even plexiform vascularity, creating a resemblance to myxoid liposarcoma especially when interspersed small fat cells were present. The most important prognostic factor was tumor location, as none of the 12 patients with a subcutaneous or intramuscular neoplasm died of tumor. Among the 49 patients with neoplasms of central body sites (mostly retroperitoneum), those with dedifferentiated liposarcoma had significantly shorter survival (median 77 mo) than those with cellular (median 142 mo) or conventional (median 209 mo) atypical lipomatous tumor, whereas there was no statistically significant difference between the latter 2 categories. Patients with atypical lipomatous tumor (either cellular or conventional) in central body sites had significantly shorter survival if the tumor transformed into dedifferentiated liposarcoma in recurrence, and, conversely, those with central body site dedifferentiated liposarcoma had significantly longer survival if it recurred as atypical lipomatous tumor. Metastasis (7 cases) occurred only when the initial specimen or a recurrence demonstrated dedifferentiated liposarcoma.

From the archives of the AFIP: imaging of musculoskeletal liposarcoma with radiologic-pathologic correlation

Liposarcoma is the second most common type of soft-tissue sarcoma, accounting for 10%-35% of these lesions. The World Health Organization has categorized soft-tissue liposarcomas into five distinct histologic subtypes: well differentiated, dedifferentiated, myxoid, pleomorphic, and mixed type. Well-differentiated liposarcomas frequently demonstrate a diagnostic appearance on computed tomographic (CT) or magnetic resonance (MR) images, with a largely lipomatous mass (>75% of the lesion) and nonlipomatous components in thick septa or focal nodules. The CT or MR imaging finding of a nodular dominant focus (>1 cm in size) of nonlipomatous tissue in a well-differentiated liposarcoma suggests dedifferentiated liposarcoma, and biopsy should be directed at the nonadipose component. The high water content of myxoid liposarcoma seen at pathologic analysis and constituting the majority of the lesion is reflected at sonography, CT, and MR imaging. However, the detection of a small amount of adipose tissue in the septa or as small nodular foci superimposed on the background of myxoid tissue allows prospective diagnosis in 78%-95% of myxoid liposarcomas. Pleomorphic liposarcomas are high-grade sarcomatous lesions and typically appear as heterogeneous soft-tissue masses, although small amounts of fat are seen on MR images in 62%-75% of cases, findings that suggest the diagnosis. Mixed-type liposarcomas have features representing a combination of the other subtypes. Primary liposarcoma of bone is exceedingly rare and usually demonstrates aggressive nonspecific features, although fat may be seen. Understanding and recognition of the spectrum of appearances of the various types of musculoskeletal liposarcoma, which reflect their underlying pathologic characteristics, improves radiologic assessment and is vital for optimal patient management.

Distant metastasis in retroperitoneal dedifferentiated liposarcoma is rare and rapidly fatal: a clinicopathological study with emphasis on the low-grade myxofibrosarcoma-like pattern as an early sign of dedifferentiation

The metastatic incidence of retroperitoneal dedifferentiated liposarcoma is comparatively lower than other pleomorphic sarcomas, varying widely from 1 to 18%. Low-grade dedifferentiation resembling low-grade fibrosarcoma has been recently accepted as part of the morphologic spectrum of dedifferentiated liposarcoma and was reported to have similar metastatic and survival rates to its high-grade counterpart. We sought to determine the metastatic incidence of retroperitoneal dedifferentiated liposarcoma, the clinicopathological features related to metastasis, and their postmetastatic behavior. Of all 354 retroperitoneal liposarcoma cases diagnosed at Memorial Sloan-Kettering Cancer Center during 1982-2003, we identified seven patients developing distant metastases, occurring in four females and three males, ranging from 35 to 73 years in age at presentation. They were all de novo dedifferentiated, while none of the well-differentiated liposarcoma or secondary dedifferentiated liposarcoma developed distant metastasis. Primary tumor sizes varied from 7.5 to 25 cm. All seven patients developing metastases contained >or=50% dedifferentiated elements in the primary tumor, with a predominant morphology resembling myxofibrosarcoma in five cases. The metastatic sites included the lung in four patients, somatic soft tissue in two, and liver in one. The median metastasis-free survival was 48 months, with only two patients experiencing local recurrences before developing metastasis. Six patients died of disease at median follow-up of 53 months after diagnosis and only 5 months after their first metastases. In conclusion, retroperitoneal dedifferentiated liposarcoma have a low metastatic rate, which is strongly related to de novo dedifferentiated histology that usually constitutes a prominent component of the primary tumor. Irrespective of the grade dedifferentiated liposarcoma with myxofibrosarcoma-like features should be closely monitored. Once metastases occur, they tend to follow a rapidly fatal course.

Transperineal resection of a retroperitoneal liposarcoma presenting as a perineal mass

BACKGROUND

Liposarcomas can present as giant liposarcomas in the retroperitoneal position.

CASE

A healthy woman presented with a large recurrent proboscis-type mass at the left gluteus and underwent a transperineal resection of the mass. The patient tolerated the procedure well and was discharged after a short hospitalization.

CONCLUSION

Once invasion into adjacent structures has been ruled out, a transperineal resection of giant retroperitoneal liposarcomas can be performed.

Atypical lipomatous tumor of the lip with pleomorphic lipoma-like myxoid area, clinically simulating mucocele

Lipomatous tumor is least common in the oral cavity. We present a case of atypical lipomatous tumor arising in the lower lip of an 81-year-old male. Clinical diagnosis was mucocele. The tumor measured 12 mm in diameter with a round shape. It was solid, firm, myxomatous and translucent with a small yellowish focus in the central portion. Histologically, the tumor was a circumscribed and well-encapsulated mass with prominent myxoid matrix. The central minor portion showed a well-differentiated liposarcoma. In the myxoid area, lipoblasts and large atypical cells with dense chromatin including floret-like giant cells were seen in abundance. Atypical lipomatous tumor may be indistinguishable from pleomorphic lipoma and its distinction from the latter is based on location as well as relative abundance of floret-type giant cells and lipoblasts. According to its abundance in lipoblasts over floret-like cells, pleomorphic lipoma-like area in our case could also be a part of atypical lipomatous tumor. It may be possible to interpret myxoid change in our case as to represent a superficial counterpart of myxoid malignant fibrous histiocytoma-like change reported in the retroperitoneal lesion.

A subgroup of malignant fibrous histiocytomas is associated with genetic changes similar to those of well-differentiated liposarcomas

Increasing clinical and pathological evidence suggests that malignant fibrous histiocytomas (MFH) comprise a heterogeneous tumor group. In a series of 108 MFH tested by comparative genomic hybridization, we found in 22 tumors high-level coamplification of the 12q14 approximately q15 chromosome region with other loci, a genetics strongly reminiscent of what has been observed for well-differentiated liposarcomas. Nevertheless, these MFH differ from liposarcomas by a high recurrence of coamplified partners because coamplified loci were seen at 1p32 in nine cases, 6q23 in seven cases, and 12q24 in six cases. The same recurrence was observed in a series of dedifferentiated liposarcomas, but not in a series of well-differentiated liposarcomas. These observations demonstrate that a subgroup of MFH share a genetic partner very similar to that observed in liposarcomas, and suggest that the undifferentiated status of these tumors is closely related to the amplifications of specific chromosome loci.

TLS-CHOP target gene DOL54 expression in liposarcomas and malignant fibrous histiocytomas

Downstream of the gene for the liposarcoma-associated fusion oncoprotein 54 (DOL54) is a target gene of the myxoid liposarcoma and round cell liposarcoma (M-LPS/RC-LPS) oncogene, TLS/FUS-CHOP. The DOL54 gene product is closely associated with adipogenic differentiation. DOL54 overexpression resulted in tumorigenicity when Chinese Hamster Ovary (CHO) cells were injected subcutaneously into nude mice. The biological significance of DOL54 expression for human malignant soft tissue tumors, however, has not yet been investigated. We examined TLS-CHOP and DOL54 expression in M-LPS/RC-LPS, well-differentiated liposarcoma and malignant fibrous histiocytoma (MFH), a tumor whose cellular origin has not been determined. We observed DOL54 expression in 50% of M-LPS/RC-LPS cases (in which TLS-CHOP was also expressed) and 33% of MFH cases, suggesting that a portion of MFH lesions may either derive from adipocytic precursor cells or have the potential to undergo adipogenic differentiation. In this manner, M-LPS/RC-LPS and MFH lesions may share tumorigenic characteristics, resulting from the unscheduled expression of DOL54.

Transdifferentiation of neoplastic cells

Transdifferentiation is a process in which a stable cell's phenotype changes to that of a distinctly different cell type. It occurs during certain physiological processes and leads to transition of tumor cell phenotypes. The latter process includes neoplastic epithelial-epithelial transition, neoplastic epithelial-mesenchymal transition, neoplastic mesenchymal-epithelial transition and transition between non-neural and neural neoplastic cell. This phonomenon is exemplified in some origin-debated tumors, such as carcinosarcoma, pleomorphic adenoma, synovial sarcoma, Ewing's/pPNET, and malignant fibrohistiocytoma. We propose that differentiation disturbance of cancer cells should include not only undifferentiation and dedifferentiation, but also transdifferentiation as well. Tumor cell transdifferentiation may be influenced or determined by cellular genetic instabilities, proliferation and apoptosis, as well as by extracellular matrix and growth factors.

Relative quantitation of p53 and MDM2 gene expression in leiomyosarcoma; real-time semi-quantitative reverse transcription-polymerase chain reaction

To investigate the etiology of leiomyosarcoma, we examined abnormalities of p53 and its regulation in 13 cases of leiomyosarcoma using fresh tumor specimens. We estimated p53 and MDM2 mRNA level and MDM2 gene amplification using a real-time semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) based on the TaqMan fluorescence method. We also used immunohistochemistry (IHC) for p53 and MDM2 protein overexpression, polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and direct sequencing to detect p53 mutation. Eight of the 13 cases (62%) showed an overexpression of p53 protein on IHC and eight of 13 cases (62%) had p53 gene point mutations. Five of the 13 cases (38%) showed positive staining for MDM2 protein and only one case (7.7%) demonstrated MDM2 gene amplification. The relative p53 mRNA level of the tumors compared with normal tissue ranged from 1.14 to 12.19 arbitrary units (AU), and the MDM2 mRNA level ranged from 1.06 to 17.17 AU. The mRNA level in the p53-positive cases was higher than in the negative cases (positive: 7.70 AU on average; negative: 3.38 AU on average; P=0.0344). However, there was no significant correlation between the MDM2 mRNA level and other factors, such as p53 IHC, p53 mutation status, p53 mRNA level and MDM2 IHC. Our results indicate that p53 abnormalities are major events and that an increasing level of p53 mRNA is associated with an overexpression of p53 protein in leiomyosarcoma and they may play an important role in the tumorigenesis in this tumor.