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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.

Abdominal Neoplasms↗

Myxoid/round cell liposarcoma of the extremities. A clinicopathologic study of 29 cases with particular attention to extent of round cell liposarcoma.

Round cell liposarcoma, a high-grade sarcoma, is a poorly differentiated form of myxoid liposarcoma, which is low grade. It is not known, however, how much of a round cell component within an otherwise typical myxoid liposarcoma results in a neoplasm that behaves as a high-grade sarcoma. Twenty-nine cases of myxoid liposarcoma of the extremities with or without a component of round cell liposarcoma were studied to semiquantitate the amount of round cell component needed to adversely affect prognosis. An estimate of the percent of necrosis, round cell liposarcoma, myxoid liposarcoma, and transitional areas was obtained for each slide on all cases. Transitional areas were defined as those that displayed an increased cellularity compared with typical myxoid liposarcoma, but in which the cells remained spindled, did not have overlapping nuclear borders, and retained an easily discernible plexiform vascular pattern. The amount of necrosis was subtracted from the total material available for evaluation, and a composite estimate of the percent of round cell, myxoid, and transitional areas was obtained. Two tumors were located on the upper extremity, 27 on the lower extremity; tumor size ranged frm 3 to 30 cm (median, 14 cm). All 29 tumors had a myxoid component, with a range from 12 to 100% (median, 73%). The range of transitional component for all 29 tumors was 0 to 88% (median, 11%). Twenty-one tumors had transitional areas (range, 4-88%). The range of round cell component for all 29 tumors was 0 to 58% (median, 0%). Twelve tumors had round cell areas (range, 1-58%). Seventeen patients are either alive without disease, or died from unrelated causes at 24-202 months (median, 96 months). Twelve patients are either alive with metastases or died of disease at 10 to 180 months (median, 53 months). Patients with > 5% round cell component in their initial tumor had a statistically significant higher rate of metastasis or death due to disease than those with < or = 5% round cell liposarcoma (p = 0.05). In addition, patients with myxoid liposarcoma with transitional areas did not fare worse than those with myxoid liposarcoma alone. In conclusion, we found that a round cell component of > 5% portends a higher risk of metastasis or death from disease. Furthermore, transitional areas alone do not appear to alter the prognosis of myxoid liposarcoma. Thus, only those areas that are unequivocally round cell liposarcoma should be designated as high grade.

Adolescent↗

Liposarcoma with meningothelial-like whorls: a study of 17 cases of a distinctive histological pattern associated with dedifferentiated liposarcoma.

AIMS: We reviewed 17 cases of liposarcoma with peculiar meningothelial-like whorls to determine the pathological and clinical significance of this distinctive morphological finding. METHODS AND RESULTS: Seventeen liposarcomas with concentric whorls simulating the whorls seen in meningioma, were retrieved from the soft tissue registry of the Armed Forces Institute of Pathology. There were 10 males and seven females with a mean age of 53 years (range 24-76 years). Twelve of the 17 cases were large retroperitoneal tumours (mean 170 mm in greatest dimensions). All 17 cases had whorls. Three cases were classified as well-differentiated liposarcoma with whorls and bone formation. Five cases showed coalescing of whorls into areas which may be interpreted as low to intermediate grade dedifferentiation. Five cases had spindled areas associated with the whorls which correlate with classical intermediate to high-grade dedifferentiation. Finally, four cases had a predominant spindle cell component resembling malignant fibrous histiocytoma with focal residual possible sclerosing well-differentiated liposarcoma (scattered adipocytes, adipocytic atypia and/or floret-type giant cells). The meningothelial-like whorls were clustered or scattered throughout the tumours and ranged from 0.09 mm to over 10 mm in diameter in cases with coalescent whorls. Metaplastic bone was present within the whorls or in their immediate vicinity in 10 of 17 cases. Immunohistochemically, the whorl-forming spindle cells showed alpha-smooth muscle actin reactivity in three of seven cases but were negative for epithelial membrane antigen, CD21, and CD35 indicating lack of relationship with meningioma and dendritic reticulum cell sarcoma, other tumours that may contain whorls. Whorls with bone formation revealed cells adjacent to the bone to be positive for osteocalcin, a marker of osteoblastic phenotype. The spindle cells of the whorls were negative for CD34 and CD31, yet these highlighted numerous capillaries inside the whorls in a concentric manner. The whorl-forming cells showed moderate to high MIB-1-index and showed p53 immunoreactivity similar to the dedifferentiated areas but differed from the areas of well-differentiated liposarcoma, which were p53-negative and showed a low MIB-1-index. Follow-up (available in 65% cases) revealed seven patients with metastases or dead of the disease and five patients with one or more recurrences. CONCLUSIONS: The meningothelial-like whorls represent a mesenchymal proliferation which may undergo pericytic or myofibroblastic, or occasionally osteoblastic, differentiation in liposarcoma. These whorls do not represent dendritic or perineurial/meningothelial differentiation. The significant proliferative activity, p53 reactivity and tendency to coalesce and associate with dedifferentiated liposarcoma suggest that the meningothelial whorls may represent an early sign of dedifferentiation of liposarcoma.

Adult↗

[Myxoid liposarcoma and pleomorphic liposarcoma: cyto-histological correlations].

Myxoid liposarcoma and pleomorphic liposarcoma: cito-histological correlations. A correlative cytologic and histologic study of a myxoid liposarcoma of the shoulder in a 72 year-old man and a pleomorphic liposarcoma observed in the retroperitoneum of a 84 year-old woman, are presented. A preoperative FNAB cytology performed in both cases showed necrotic material containing spindle-stellate shaped cells, interspersed in a myxoid matrix, with rare classical monovacuolated lipoblasts and fragments of plessiform vessels were seen in the first and scattered pleomorphic and multinucleated cells, with prominent nucleoli and numerous atypical mitosis in the second. A malignant mesenchimal spindle-cells tumor, with myxoid matrix and pleomorphic cells, consistent with liposarcoma, respectively were suspected. Gross and histological specimens confirmed the cytological suspect. Authors discuss main cyto-histological differential diagnoses of myxoid tumors, and point out the importance and a correct differentiation between myxoid liposarcoma and intramuscular myxoma. The cytologic appearance of pleomorphic liposarcoma is similar to histologic type and therefore the problem of a differential diagnosis with soft tissue tumors is analogous. When mono or plurivacuolated lipoblasts are absent, differential diagnosis between pleomorphic histiocytoma and liposarcoma is impossible. Nevertheless this is not a important problem at cytological level because both tumors have a had prognosis and must be treated with radical surgery. Definition of correct histologic type will be more suitable on histologic specimens.

Aged↗

Liposarcoma initiated by FUS/TLS-CHOP: the FUS/TLS domain plays a critical role in the pathogenesis of liposarcoma.

The most common chromosomal translocation in liposarcomas, t(12;16)(q13;p11), creates the FUS/TLS-CHOP fusion gene. We previously developed a mouse model of liposarcoma by expressing FUS-CHOP in murine mesenchymal stem cells. In order to understand how FUS-CHOP can initiate liposarcoma, we have now generated transgenic mice expressing altered forms of the FUS-CHOP protein. Transgenic mice expressing high levels of CHOP, which lacks the FUS domain, do not develop any tumor despite its tumorigenicity in vitro and widespread activity of the EF1alpha promoter. These animals consistently show the accumulation of a glycoprotein material within the terminally differentiated adipocytes, a characteristic figure of liposarcomas associated with FUS-CHOP. On the contrary, transgenic mice expressing the altered form of FUS-CHOP created by the in frame fusion of the FUS domain to the carboxy end of CHOP (CHOP-FUS) developed liposarcomas. No tumors of other tissues were found in these transgenic mice despite widespread activity of the EF1alpha promoter. The characteristics of the liposarcomas arising in the CHOP-FUS mice were very similar to those previously observed in our FUS-CHOP transgenic mice indicating that the FUS domain is required not only for transformation but also influences the phenotype of the tumor cells. These results provide evidence that the FUS domain of FUS-CHOP plays a specific and critical role in the pathogenesis of liposarcoma.

Adipocytes↗

S-100 protein distribution in liposarcoma. An immunoperoxidase study with special reference to the distinction of liposarcoma from myxoid malignant fibrous histiocytoma.

The presence and distribution of S-100 protein were studied in 63 cases of liposarcoma and 20 cases of myxoid malignant fibrous histiocytoma (MFH), using the immunoperoxidase technique. Normal adipose tissue and benign lipomatous tumours were also studied by the same technique, for purposes of comparison. In all liposarcomas, most of the adipocytes and vacuolated lipoblasts were positive for S-100 protein, although the tumour cells in non-lipogenic areas of dedifferentiated liposarcoma and the non-vacuolated giant cells with a deeply eosinophilic cytoplasm in the pleomorphic liposarcomas were devoid of S-100 protein immunoreaction products. One third of the myxoid type liposarcomas contained numerous immunoreactive, immature-appearing spindle or oval cells, reminiscent of the primitive fat organs of white adipose tissue. Conversely, none of the myxoid MFHs contained S-100 protein in the tumour cells, including the irregularly vacuolated ones. These results suggests that the immunohistochemical demonstration of S-100 protein is a useful diagnostic tool, particularly for the assessment of vacuolated tumour cells and for the diagnosis of myxoid tumours.

Adipose Tissue↗

Translocation t(12;16)(q13;p11) in myxoid liposarcoma and round cell liposarcoma: molecular and cytogenetic analysis.

Translocation t(12;16)(q13;p11) is regarded as a diagnostic marker for myxoid liposarcoma. Cytogenetic data on round cell liposarcomas and combined myxoid and round cell tumors is scarce, and the genetic basis of progression of myxoid tumors to high grade, round cell lesions is unknown. We have accumulated six round cell, four combined myxoid and round cell, and three myxoid liposarcomas for analysis. t(12;16)(q13;p11) was present in three round cell lesions and was detectable in all of the tumors by DNA analysis. In each tumor type, the CHOP gene in 12q13 was rearranged and fused to the TLS gene in 16p11. A variant TLS-CHOP RNA transcript was detected by polymerase chain reaction but did not correlate with clinicopathological data. No distinguishing cytogenetic or molecular markers for round cell or mixed lesions were found. The histogenic and genetic relatedness of myxoid and round cell liposarcomas is apparent from these data.

Adult↗

Spindle cell liposarcoma, a hitherto unrecognized variant of liposarcoma. Analysis of six cases.

A series of six cases of a previously unrecognized variant of liposarcoma characterized by a prominent spindle cell component is reported herein. Clinically, all of the tumors arose in adults and developed around the shoulder girdle or upper limbs; all but one arose in subcutaneous tissue. Three patients developed multiple local recurrences over a period of 4-20 years. Recurrences in one case were purely lipoma-like. Following dedifferentiation in a recurrence, one patient developed distant metastases and eventually died, 46 months after the primary excision. Grossly, these lesions are characterized by multinodularity, and microscopically they show a relatively bland spindle cell proliferation arranged in fascicles and whorls and set in a variably myxoid stroma. The spindle cell areas are accompanied by an adipocytic component, which exhibits the morphologic features required for inclusion in the well-differentiated liposarcoma-atypical lipoma group, including definite lipoblasts. Main differential diagnoses include benign lesions such as spindle cell lipoma and diffuse neurofibroma, as well as dermatofibrosarcoma protuberans and other malignancies such as sclerosing liposarcoma, low-grade myxofibrosarcoma, low-grade malignant peripheral nerve sheath tumor, and low-grade fibromyxoid sarcoma. In view of their distinctive histologic appearance, and because aggressive clinical behavior was observed despite their superficial location, we propose that these lesions be regarded as spindle cell variants of well-differentiated liposarcoma.

Adult↗

Atypical lipoma, atypical intramuscular lipoma, and well differentiated retroperitoneal liposarcoma: a reappraisal of 30 cases formerly classified as well differentiated liposarcoma.

Thirty cases formerly diagnosed as Grade I lipogenic liposarcoma (well differentiated liposarcoma) were reviewed. The basic histologic pattern in all was that of adult fat modified by the presence of cells with enlarged, hyperchromatic nuclei; in most cases there was also a component of myxoid and/or fibrous tissue. The length of follow-up ranged from two to 30 years. Nine of the tumors were located in the subcutaneous layer. None of these recurred after excision, not even those which were simply "shelled out," and none metastasized. The term "atypical lipoma" is proposed for this group. Thirteen were located within or between muscles of the limbs, limb girdles, and head and neck. Nine of these recurred at least one, but there were no metastases and no deaths due to tumor. These were designated "atypical intramuscular lipoma." The remaining eight originated in the retroperitoneum. Although none of these patients developed metastases, five suffered inoperable recurrence and three died as a result of the neoplasm. It is suggested that the term "well differentiated retroperitoneal liposarcoma" be retained for cases of this type.

Adult↗

Pancreatic liposarcoma: case report with review of retroperitoneal liposarcomas.

A case report of a large pancreatic liposarcoma is presented showing a five-year survival with aggressive surgical excision as the only treatment. The medical literature of the subject is reviewed. This is the only reported case of retroperitoneal liposarcoma which is limited to the pancreas. A discussion of the current types of treatment for retroperitoneal liposarcomas is included.

Female↗

Epithelioid variant of pleomorphic liposarcoma: a study of 12 cases of a distinctive variant of high-grade liposarcoma.

We describe 12 patients with a distinctive variant of pleomorphic liposarcoma that histologically shows epithelioid features and focally resembles a solid carcinoma. The tumors occurred in nine men and three women (median age, 63 yr; range, 40-78 yr). Five tumors were in the thigh, two in the chest wall, two in the axilla, and one each in the retroperitoneum, groin, and calf. Most were 15 to 20 cm in maximal diameter. They consisted of sheets of epithelioid-appearing cells with ample, variably eosinophilic cytoplasm, often showing a honeycomb-like pattern of cell borders and little if any collagenous extracellular matrix. Their histologic features often resembled those of renal clear cell carcinoma or adrenal cortical carcinoma, but all showed evidence of adipocytic differentiation, and five also showed focal spindle cell components. One patient whose tumor in the thigh had been originally diagnosed as metastatic renal carcinoma had undergone nephrectomy without a finding of a kidney tumor. All of the cases were positive for vimentin; 6 of 11 cases were positive for S-100 protein, usually focally; 5 of 11 were focally positive for keratins; and all were negative for epithelial membrane antigen, muscle actins, desmin, and CD34. High mitotic activity (mean, 42 mitotic figures per 10 high power fields) and high MIB-1-positive proliferative fraction (>30%) were seen in all of the cases, and nuclear p53 immunoreactivity was detected in five of seven cases. Of the eight patients with complete follow-up, five died of disease (median survival, 6 mo), two died of unrelated causes 10 and 18 years later, and 1 was alive and well 24 years later. The epithelioid variant of pleomorphic liposarcoma is a high-grade tumor that must be distinguished from malignant epithelial tumors, especially in view of the keratin immunoreactivity of some of these neoplasms.

Adult↗

[Liposarcoma of the spermatic cord. Review of the literature. Apropos of a case of myxoid liposarcoma].

Based on one case of spermatic cord liposarcoma, the authors mention the different histological types of this lesion. A review of the literature confirms this rare tumor typically occurs in the adult population; the majority of spermatic cord liposarcomas are of low grade malignancy. The treatment of choice remains radical orchidectomy with wide excision of the tumor. Because of the predilection of this lesion for local recurrence, the patients must be followed periodically.

Genital Neoplasms, Male↗

Specificity of TLS-CHOP rearrangement for classic myxoid/round cell liposarcoma: absence in predominantly myxoid well-differentiated liposarcomas.

Myxoid liposarcoma (LS), the most common subtype of LS, is known to be characterized by the specific t(12;16) resulting in a TLS-CHOP fusion in almost all cases. We wished to address the following questions: (i) Is this genetic hallmark also present in other types of LS with predominant myxoid change? (ii) What is the proportion of cases with the variant EWS-CHOP fusion? (iii) What is the optimal approach for Southern blot detection of TLS breakpoints? We identified 59 LS characterized histologically by >90% myxoid component, in which frozen tissue tumor was available for DNA extraction. These 59 LS with myxoid features were divided into 2 groups: 42 LS with classic myxoid/round cell appearance (myxoid LS) and 17 well-differentiated LS (WDLS) with a predominant (>90%) myxoid component. Within the myxoid LS group, 29 tumors were low grade and 13 high grade (>20% round cell component). Among the 17 predominantly myxoid WDLS, there were 15 low grade and 2 focally high grade tumors. In addition, we selected as control group, 20 LS of other histological types with minimal or no myxoid change (17 WDLS and 3 pleomorphic LS) and 13 myxofibrosarcomas. Southern blot analysis was performed in all cases using a CHOP cDNA probe, and in all CHOP rearranged cases using a TLS cDNA probe. Probe/enzyme combinations for Southern blot analysis were CHOP exon 3-4 cDNA probe with BamHI or SacI, TLS exon 3-6 cDNA probe with BclI. All 42 cases of myxoid LS showed a CHOP rearrangement and 38 of them also had a TLS rearrangement. Among the 4 myxoid LS without Southern blot evidence of TLS rearrangement, 1 showed an EWS-CHOP fusion by Southern blotting and reverse transcriptase-polymerase chain reaction and in another case, reverse transcriptase-polymerase chain reaction detected a TLS-CHOP fusion transcript. None of the predominantly myxoid WDLS and none of the tumors included in the control group showed rearranegements with CHOP probe. In addition, 12 predominantly myxoid WDLS, 10 other LS, and 5 myxofibrosarcoma from the control group were also tested for TLS rearrangement; all were negative. The TLS-CHOP fusion is highly sensitive and specific for the entity of classic myxoid/round cell LS. Other types of LS, even with a predominant myxoid component, lack the TLS-CHOP rearrangement, confirming that they represent a genetically distinct group of LS. The prevalence of the EWS-CHOP variant fusion was approximately 2% in this series. The optimal enzyme for TLS genomic breakpoint detection is BclI.

Blotting, Southern↗