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[Lipomatous tumors of the skin and soft tissue. New entities and concepts].

Mesenchymal neoplasms of lipogenic differentiation are the most common soft-tissue neoplasms in adults. In recent years a number of "new" entities and variants have been described. Their recognition is important to avoid diagnostic pitfalls and inappropriate therapy. Chondroid lipoma, myolipoma, and purely cutaneous spindle-cell/pleomorphic lipoma are biologically benign neoplasms which may mimic sarcomas morphologically. Despite high-grade morphology cutaneous liposarcomas carry a favorable clinical prognosis. Spindle cell liposarcoma is a rare variant of atypical lipomatous tumour (well-differentiated liposarcoma) and must be distinguished from dedifferentiated liposarcoma with metastatic potential and benign spindle cell lipoma. The advent of cytogenetic and molecular investigations of lipomatous neoplasms has contributed to a better understanding of the biology of these neoplasms and led to a modification of conventional classification schemes.

Diagnosis, Differential↗

Lipomatous tumors: a correlative cytologic and histologic study of 27 tumors examined by fine needle aspiration cytology.

A correlative cytologic and histologic study of 12 benign lipomatous tumors and 15 liposarcomas (well-differentiated, myxoid, round cell, and pleomorphic) is presented. In two cases the fine needle aspiration material was embedded in Epon for light and electron microscopic examination. Good correlation was found between the histologic and cytologic findings in the fine needle aspiration material. Pitfalls in the cytologic diagnosis of regressively changed lipoma, intramuscular lipoma, angiolipoma, hibernoma, and lipoblastoma, which may lead to an erroneous diagnosis of liposarcoma, are illustrated. The cytologic appearances of the liposarcomas varied with histologic type, although in all of these tumors the main criterion was the presence of atypical multivacuolated lipoblasts with characteristically scalloped nuclei. Staining of the aspirated material with Alcian blue at varying pH levels for characterization of the glycosaminoglycan content may help in the distinction of myxoid liposarcomas from myxoid chondromatous tumors and chordomas. May-Grünewald-Giemsa staining is considered the most useful staining method, while fat staining is considered of limited or no value in the cytologic diagnosis of lipomatous tumors. Epon embedding of fine needle aspirates for light and electron microscopic examination seems to be a useful diagnostic technique.

Adolescent↗

Myolipoma of the retroperitoneum.

A case of retroperitoneal myolipoma is reported. A 55-year-old woman with the main complaint of an abdominal mass was admitted to Teikyo University Hospital, Tokyo, Japan. Retroperitoneal liposarcoma was suspected based on magnetic resonance imaging, and the tumor was resected. The resected tumor was well encapsulated and 30 x 15 x 8 cm in size. Histologically, it consisted of mature adipose cells and smooth muscle cells. Neither nuclear atypia nor mitosis was observed in either component. The tumor was pathologically diagnosed as myolipoma of the retroperitoneum. Retroperitoneal myolipoma is often misdiagnosed radiologically as liposarcoma because the overwhelming majority of large retroperitoneal tumor containing fat is liposarcoma, however, the clinical course of myolipoma is quite different from that of liposarcoma. Although myolipoma is very rare, pathologists should consider it in the differential diagnosis of fat-containing retroperitoneal masses.

Diagnosis, Differential↗

Matrix "blues": clue to a cranial thoracic mass in a dog.

A 5-year-old, intact male Italian Spinone dog was presented for progressive, severe dyspnea and coughing. Thoracic radiographs revealed a large mass in the right cranial thorax. Fine needle aspiration of the mass yielded a highly cellular sample containing dense clumps of oval to spindle-shaped mesenchymal cells with distinct intracytoplasmic vacuolation, consistent with lipoblasts and lipocytes. Cell clusters were associated with abundant eosinophilic matrix, which was identified as mucin, based on Alcian blue staining. At exploratory thoracotomy, the mass was found to be nonresectable, and the dog was euthanized. Histologic sections of the multilobular mass had discrete regions of variable cellular differentiation, including highly cellular areas of pleomorphic cells, areas of spindle cells and lipoblasts in a myxoid background, and areas of well-differentiated lipogenic cells. The histologic diagnosis was myxoid liposarcoma. The thoracic cavity is a rare site for liposarcoma in the dog. The cytologic features of lipoblasts together with a mucopolysaccharide matrix were useful for distinguishing the myxoid variant of liposarcoma from other forms of liposarcoma and myxoid sarcomas.

Animals↗

Multiple recurrences of a lesion at the base of the tongue.

A patient with a well-differentiated liposarcoma at the base of the tongue is reported. The patient experienced many local recurrences over 37 years yet remained free of metastases. Liposarcomas of the oral cavity are rare and are not usually included in the differential diagnosis of soft tissue masses in the oral region. As these tumors may occur anywhere that adipose tissue is found, the possibility of a slowly enlarging asymptomatic, grossly well-defined, soft to firm mass being a liposarcoma must be remembered. Because of the difficulties sometimes experienced in histologically distinguishing between low-grade well-differentiated liposarcoma and certain lipomas, any recurrence of a lipoma should be viewed with a great deal of suspicion about the original diagnosis.

Diagnosis, Differential↗

[Gastric tumors with fatty components. CT findings and differential diagnosis].

PURPOSE: To assess the role of CT in diagnosing and characterizing gastric fatty tumors. MATERIAL AND METHODS: We reviewed the CT scans of 16 patients (8 men, 8 women, mean age 52 years) with gastric fatty tumors (11 lipomas, 3 liposarcomas, 1 angiolipoma, 1 teratoma) examined from 1990 to 1999. The differential diagnosis considered primary and secondary lipomatosis, carcinoma engulfing the perivisceral fat and thus mimicking a liposarcoma, mesenchymal gastric and primary peritoneal tumors. RESULTS: Lipomas involved the fundus (7/11), the body (3/11), the antrum (1/11). Multifocality was found in one case. Lesions size ranged 25 to 65 mm (mean 35 mm). All the lipomas showed homogeneous structure with negative (-30 -100) HU values. A pseudocapsule was demonstrated in 7/11 cases. No infiltrative growth was demonstrated. The angiolipoma located in the fundus showed a vascular component with strong contrast enhancement. All the liposarcomas were bigger than 10 cm and there was a strong correlation between pathologic specimen and CT findings. The differentiated liposarcomas showed the classic heterogeneous fatty density; on the contrary the myxoid and the pleomorphic types showed an aspecific structure with necrotic/cystic changes, mostly demonstrated in the myxoid type. The teratoma was a solid mass with fatty, solid, necrotic and calcified components. CONCLUSION: CT allows the diagnosis and characterization of gastric fatty tumors. The preoperative diagnosis of lipomas plays a major clinical role because it often makes surgery unnecessary.

Adult↗

What to do with deep lipomatous tumors.

Although most deep soft-tissue sarcomas are fairly easily recognized as heterogenous masses that are bright on T2-weighted MRI and dark on T1-weighted MRI, liposarcomas are often difficult to distinguish from lipomas and other benign fatty tumors. Because clinical features overlap considerably between lipomas and liposarcomas, the radiographic features are of utmost importance in differentiating these entities. Key MRI features, such as homogeneity of fatty signal, absence of gadolinium enhancement, and low signal on short tau inversion recovery images, strongly support the diagnosis of benign lipoma, but the absence of these findings is not specific for liposarcoma. Unfortunately, biopsy frequently results in false negative findings; therefore, early referral to an orthopaedic oncologist is indicated when any radiographic features suggest that the mass could represent a liposarcoma.

Biopsy↗

A light and electron microscopic study with comments on their relation to malignant fibrous histiocytoma and angiosarcoma.

Analysis of 365 cases of malignant soft tissue tumors revealed 83 cases of liposarcoma. The ages of the patients were distributed between 18 and 86 years with a mean average of 54.3 years. Approximately 50% of the cases were located in the lower extremity. Histologically, they consisted of 5 types; well differentiated (17 cases), myxoid (49 cases), round cell (3 cases), pleomorphic (11 cases), and mixed (3 cases). The appearance of lipoblasts of either the signet-ring type or mulberry (multivacuolated) type with displaced nuclei was the common characteristic feature for all types. Electron microscopically, lipid droplets were found inside of endoplasmic reticulum in lipoblasts, and abundant glycogen granules were seen in the cells containing only few lipid droplets. The lipoblasts were usually located close to the vascular wall in the interstitium, and findings suggesting an intimate relation between pericytes and lipoblasts were encountered. Although the differential diagnosis of malignant fibrous histiocytoma and liposarcoma was made possible by the appearance of lipoblasts in the latter, storiform pattern and histiocyte-like cells sometimes appeared in poorly differentiated liposarcoma. This tendency was also found in angiosarcoma. A close follow-up of recurrent cases revealed that there are actually cases of liposarcoma with malignant fibrous histiocytoma-like pattern and angiosarcoma with malignant fibrous histiocytoma-like pattern. It was considered that malignant fibrous histiocytoma-like figures can appear in various poorly differentiated sarcomas.

Adult↗

Sporadic amplification of the c-fms proto-oncogene in human musculoskeletal sarcomas.

Fresh samples of bone and soft tissue sarcoma from 31 patients were analyzed by the Southern technique for amplification or other structural abnormalities of the c-fms oncogene. As a sole finding, amplification of the c-fms (4- and 10-fold) was detected in 2 of 3 cases with a histologic diagnosis of liposarcoma. RFLP analysis disclosed no gene rearrangements associated with the c-fms amplification. The case with the highest amplification of the c-fms gene was disease-free at review. The 2 fms-amplified liposarcomas were aneuploid according to DNA flow cytometry. This is the first study demonstrating amplification of the c-fms proto-oncogene in human liposarcoma. The fact that this structural abnormality of the c-fms gene was only detected in liposarcomas might point to an uncommon but tissue-specific phenomenon.

Blotting, Southern↗

Cytogenetic findings in pediatric adipose tumors: consistent rearrangement of chromosome 8 in lipoblastoma.

Characteristic cytogenetic aberrations have been reported in adult lipomas and liposarcomas, but few karyotypes have been reported for pediatric adipose neoplasms. In this report we describe a consistent rearrangement, der(8)(pter-->q13::q24.1-->qter), in 2 of 3 lipoblastomas. A similar der(8) was present in the only other published lipoblastoma karyotype, but this der(8) has not been reported in lipomas, liposarcomas, or nonadipose solid tumors. We investigated the potential specificity of der(8)(pter-->q13::q24.1-->qter) by karyotyping an unselected series of nonlipoblastoma adipose tumors in children and young adults. The series included 14 lipomas, 2 atypical lipomas ("well-differentiated liposarcomas"), and 2 angiomyolipomas; der(8) was not found in any tumor from this series. Three lipomas, however, contained rearrangements in the region of chromosome band 12q14, as has been described frequently in adult lipomas. Because clinical features in lipoblastoma can mimic those in liposarcoma, recognition of der(8)(pter-->q13::q24.1--qter) is of potential diagnostic relevance.

Child, Preschool↗

No rearrangements of the CHOP gene in malignant fibrous histiocytoma.

The human transcription factor gene, CHOP, which maps to 12q13, was recently shown to be disrupted by the t(12;16)(q13;p11) in myxoid liposarcoma. The most common soft tissue sarcoma, malignant fibrous histiocytoma (MFH) histopathologically may contain liposarcoma like areas and is often characterized by complex chromosome anomalies, which may include 12q13-15 aberrations, but never as t(12;16). By Southern blot technique, we detected no rearrangements of the CHOP gene in 41 MFH, including five with liposarcoma like areas. Thus, rearrangements of the CHOP gene appear to be specific for myxoid liposarcoma with t(12;16) and are not associated with lipoblastic differentiation.

CCAAT-Enhancer-Binding Proteins↗

Lipoblastoma and lipoblastomatosis in infancy and childhood: histopathologic, ultrastructural, and cytogenetic features.

Lipoblastoma is a relatively rare tumor that occurs in infancy and early childhood and arises from embryonic white fat. Although a benign tumor, lipoblastomas tend to recur and may resemble myxoid liposarcoma. The authors report 26 cases over a 15-year period at Texas Children's Hospital. There was a slight female predilection (14F:12M). The most common symptom was a painless mass with or without increasing size. The trunk, extremities, head and neck, retroperitoneum, inguinal canal, peritoneal cavity, and lung were the tumor sites. Most tumors were circumscribed lipoblastomas and the minority were diffuse infiltrative lipoblastomatosis. Reexcision for residual or recurrent tumor was necessary more frequently in patients with lipoblastomatosis. Histopathologic examination and ultrastructural examination revealed cellular neoplasms composed of immature adipocytes with relatively well-defined septa, frequent lipoblasts, a fine vascular network, and often a myxoid appearance resembling myxoid liposarcoma. Cytogenetics was performed in 4 cases with chromosome 8q abnormality being most common. The major concern with lipoblastoma in children is to completely excise the tumor to avoid leaving residual tumor and to prevent recurrences. Confusion with myxoid liposarcoma, well-differentiated liposarcoma, and typical lipomas may occur. Although asymptomatic, lipoblastomas may cause dysfunction of other organ systems due to mass effect. Complete surgical excision with at least 2 years of follow-up is the preferred therapy.

Age Factors↗

Retroperitoneal sarcomas.

Retroperitoneal sarcomas are rare neoplasms. CT or MR imaging is performed in patients with these tumors to detect local extent and distant metastases of the tumor and for preoperative surgical planning. Most sarcomas cannot be characterized as to cell type with CT or MR, with the exceptions being liposarcomas and intracaval leiomyosarcomas. Similarly histological grading cannot be made definitively with imaging alone, the exception being liposarcoma since well differentiated liposarcomas contain more macroscopic fat than do less differentiated liposarcomas. After surgery, follow up imaging with CT or MR and careful scrutiny of the tumor bed and resection site are essential to detect early recurrences, which can often be managed with re-resection.

Diagnostic Imaging↗

Chromosomal translocations in human soft tissue sarcomas by interphase fluorescence in situ hybridization.

In soft tissue sarcomas, clonal rearrangement of chromosomes has been shown by cytogenetic analysis to be unique and specific for tumor types. The development of fluorescence in situ hybridization (FISH) has allowed detection of chromosomal rearrangements in the interphase nuclei isolated from paraffin-embedded tissues. Three kinds of translocations in the interphase nuclei that were isolated from 47 cases of soft tissue sarcomas were examined by FISH with chromosome-specific DNA probes of centromeric and total probes. Of 47 soft tissue sarcomas 42 (89.4%) revealed tumor-specific translocations by retrospective cytogenetic analysis. Translocation t(X;18) was detected in 25/28 synovial sarcomas; translocation t(11;22) in 5/6 Ewing's sarcomas and primitive neuroectodermal tumors (PNET); and translocation t(12;16) was found in 12/13 liposarcomas, including 10 myxoid and two round cell types as clonal chromosomal aberrations specific for both subtypes. Based on the cytogenetic analysis, Ewing's sarcoma is related closely with PNET as shown by MIC2-protein reactivity. Other cytogenetic findings of translocation t(12;16) indicate that round cell liposarcomas share chromosomal changes with myxoid liposarcomas, and further suggest that both tumor subtypes of liposarcoma may possess common precursor cells. FISH is a useful aid in determining the tumor type of soft tissue sarcomas with regard to histogenetic origin.

Adolescent↗

Prognostic significance of augmented metallothionein (MT) expression correlated with Ki-67 antigen expression in selected soft tissue sarcomas.

In soft tissue sarcomas, the most important prognostic criteria include extent of malignancy (G), size of the tumour and intensity of Ki-67 antigen expression. In recent times expression of metallothionein (MT) in cells of some malignant processes of epithelial origin was found to correlate with intensity of Ki-67 antigen expression and to carry a possible prognostic significance. The present study aimed at a demonstration of prognostic value of MT expression and at comparing it with Ki-67 antigen expression and G grade in selected soft tissue sarcomas. Immunohistochemical studies were performed on paraffin sections in 54 cases of malignant fibrous histiocytoma (MFH), 18 cases of liposarcoma and 20 cases of synovial sarcoma. The extent of MT and Ki-67 antigen expression was evaluated and an attempt was made to correlate the results with each other and with grade of the tumour. Expression of MT was evident both in the cytoplasm and in cell nuclei of all studied sarcomas. The most pronounced MT expression was noted in MFH-type tumours. The extent of Ki-67 antigen expression was similar in MFH and liposarcoma and was the lowest in synovial sarcoma. In MFH, liposarcoma and synovial sarcoma a pronounced positive correlation was documented between expression of MT and Ki-67 antigen (r=0.85; p<0.001; r=0.93, p<0.0001; r=0.79, p<0.0001). In all types of the tumours a positive relation was detected between MT expression, expression of Ki-67 and G grade of malignancy in the tumour. Moreover, patients with higher MT expression in the studied tumours demonstrated a shorter survival. MT expression in soft tissue tumours of MFH, liposarcoma and synovial sarcoma type strongly correlated with intensity of proliferation (Ki-67) and G grade and could be useful in defining the extent of malignancy and in prognostic appraisal in the tumours.

Humans↗

[CT manifestations of primary hepatic sarcoma].

OBJECTIVE: To assess the diagnostic value of CT to primary hepatic sarcoma. METHODS: The CT findings of 12 cases of primary hepatic sarcomas confirmed by operation and pathology, including leimyosarcoma, liposarcoma, and malignant fibrous histocytoma, 2 cases each, and angiosarcoma, carcinosarcoma, cystadenocarcinosarcoma, mesotheliosarcoma, fibrosarcoma, and malignant lymphoma, one case each, were analysed retrospectively. RESULTS: Only 2 out of the 12 cases of primary hepatic sarcoma were correctly diagnosed by CT before operation. The CT manifestations of primary hepatic sarcoma, against the operational and pathological findings, could be summarized as two types: solid mass type and cystic mass type. Eight cases were of solid mass type, including 2 cases of liposarcoma, and leiomyosarcoma, angiosarcoma, carcinosarcoma, methotheliosarcoma, fibrosarcoma, and malignant lymphoma, one case each. Plain scanning showed homogeneous or inhomogeneous low-density masses; enhanced scanning showed no marked enhancement or inhomogeneous enhancement, ringed peripheral enhancement, or nodular peripheral enhancement. Peripheral enhancement was a CT feature common to angiosarcoma and lymphoma. The characteristic CT manifestation of liposarcoma was an inhomogeneous mass with well-defined border and multiple intermingled septa. Four cases were of cystic mass type, including 2 cases of malignant fibrous histocytoma, and leimyosarcoma with post-operative recurrence and cystadenocarcinosarcoma, one case each, all manifesting a huge single cystic mass: unilocular in the case of leimyosarcoma with post-operative recurrence and multilocular in the other 3 cases. The wall and/or septa of the cyst had an uneven thickness and were markedly enhanced after contrast administration. Clear solid element and wall nodules were seen in the cystic mass of cystadenocarcinosarcoma. CONCLUSION: The CT findings of primary hepatic sarcoma are associated with the pathology of tumor. Some pathological patterns of primary hepatic sarcoma, such as liposarcoma and angiosarcoma, have their own characteristic CT manifestations. However, the diagnosis of most primary hepatic sarcoma lacking characteristic CT manifestations must be based on clinical and laboratory examinations and confirmed by pathology.

Adolescent↗

Oncogenic transformation and inhibition of adipocytic conversion of preadipocytes by TLS/FUS-CHOP type II chimeric protein.

Myxoid liposarcomas are characterized by t(12; 16)(q13;p11) translocation and expression of TLS/ FUS-CHOP chimeric transcripts (types I to III). Among these, the type II transcript is expressed in the majority of cases of myxoid and round cell liposarcoma. To investigate the function of the type II chimeric protein, we obtained stable transformants of ST-13, a murine preadipocytic cell line, which express TLS/FUS-CHOP type II protein (ST-TC) or CHOP protein (ST-C) as well as vector-transfected controls (ST-V). ST-TC and ST-C cells showed almost complete or partial resistance to adipogenic conversion by insulin and thiazolidinedione, respectively. Induction by adipogenic stimulation of the adipocytic genes such as C/EBP alpha, aP2, and adipsin was almost totally suppressed in the ST-TC cells, whereas in ST-C cells C/EBP alpha alone was induced without induction of aP2 and adipsin. Transcriptional suppression of the C/EBP alpha gene in ST-TC cells was suggested by the results of chloramphenicol acetyltransferase (CAT) assay showing a significantly lower C/EBP alpha promoter activity compared with findings in ST-C and ST-V cells. Failure to rescue adipogenic conversion by ectopic expression of C/EBP alpha in ST-TC cells suggested a functional impairment of C/EBP alpha to induce expression of downstream genes. TLS/FUS-CHOP type II protein showed transforming activity, as evidenced by loss of contact inhibition of growth, anchorage-independent growth in soft agar, and tumor formation in nude mice, showing typical histological features of myxoid liposarcoma seen in humans. These findings suggest important roles for TLS/FUS-CHOP type II protein in the oncogenesis of myxoid liposarcoma.

Adipocytes↗

[Genetic studies of differential fatty tissue tumor diagnosis].

Adipose tissue tumors are often characterized by typical or even specific chromosomal alterations. In some of the cases the molecular background of these microscopically visible alterations was already elucidated. In myxoid liposarcomas the translocation t(12;16) creates a fusion gene between the CHOP gene and the FUS gene and in lipomas the HMGI-C gene becomes rearranged by structural aberrations involving chromosomal region 12q14-15. Based on examples of a lipoma, a well-differentiated liposarcoma, a myxoid liposarcoma, and an aggressive angiomyxoma it is demonstrated in the present paper how cytogenetic investigation can be used as an additional tool for an improved diagnosis of adipose tissue tumors. Furthermore, the detection of molecular mechanisms underlying the visible cytogenetic alterations will certainly significantly increase our knowledge about the pathogenesis of these diseases.

Adult↗