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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

The ultrastructure of liposarcoma. A study of 10 cases.

An ultrastructural study of 10 liposarcomas is reported. Four of the liposarcomas were wholly or predominantly of well-differentiated, lipoma-like or fibrosing type, 3 of myxoid type, 2 of round cell type and 1 pleomorphic type. The well-differentiated, lipoma-like liposarcomas showed cells with a few, large lipid droplets, few organelles and a peripherally located, fairly large nucleus, The well-differentiated liposarcomas of fibrosing type revealed mostly spindle-shaped, fibroblast-like cells, with abundant rough endoplasmic reticulum and inconspicuous lipid inclusions, surrounded by collagen. One well-differentiated liposarcoma contained an area which was similar to brown adipose tissue and hibernoma. The spindle and stellate shaped cells of the myxoid liposarcomas showed abundant rough endoplasmic reticulum and large smooth-membraned vacuoles filled with moderately dense amorphous material, which appeared to be extruded extracellularly by rupture of the vacuoles. Cytoplasmic lipid droplets were seen in most cells but were much less prominent than in the well-differentiated lipoma-like liposarcomas. Ultrastructurally there were many similarities between the myxoid and round cell liposarcoma, indicating a close relationship between the two types. The pleomorphic liposarcoma revealed cells with one or more large, irregular nuclei, numerous large vacuoles after dissolved lipids, abundant dilated cisternae of rough endoplasmic reticulum and rounded, electron-dense bodies corresponding to PAS-positive hyalin globules seen in the light microscope. The ultrastructural study suggests that the variegated cellular appearance of the different subtypes of liposarcoma reflects the wide cellular spectrum seen during the differentiation of adipose tissue and supports the view that all liposarcomas histogenetically represent a single entity.

Adipose Tissue

Liposarcoma a clinicopathologic, radiographic and prognostic study.

The present investigation is a clinicopathologic, radiologic and prognostic study of 122 liposarcomas registered in the Swedish Cancer Registry between 1958 and 1966. The incidence of liposarcoma in Sweden was estimated to be 2.5 cases per million inhabitants per year. The liposarcomas were divided into 4 main subtypes according to WHO's recommended classification (1969): well-differentiated (33 cases), myxoid (22 cases), rundcell (14 cases) and pleomorphic types (21 cases). When predominantly well-differentiated or myxoid liposarcomas contained areas of round-cell or pleomorphic types (24 and 8 cases, respectively), they were classified separately, thus adding 2 further subtypes to our classification. The validity of this histologic classification was emphasized by the prognostic study, based on a 10 year follow-up. The differential diagnosis for each of the 4 main subtypes is discussed. Three well-differentiated, lipoma-like liposarcomas which contained highly vascular hibernoma-like areas are described. Two well-differentiated liposarcomas situated in the neck and upper part of the back, respectively, of elderly patients included area similar to "spindle-cell lipoma" (Enzinger). An intracytoplasmic network of birefringent fibers with the staining reaction of collagen was found in 2 well-differentiated fibrosing liposarcomas...

Adolescent

Cytogenetic findings in liposarcoma correlate with histopathologic subtypes.

The cytogenetic findings in 31 liposarcomas from 26 patients are reported. Four other tumors did not grow. Three histologic types are represented in this analysis. The well-differentiated liposarcomas were characterized by telomeric associations, large marker chromosomes and ring chromosomes, and in some cases, double minutes. The pleomorphic liposarcomas contained very high clonal chromosomal numbers with near-tetraploid modes and numerous variable, often unidentifiable, chromosomal abnormalities. The myxoid liposarcomas were characterized primarily by a t(12;16)(q13;p11) as the sole abnormality or additional changes. These results indicate that cytogenetic findings may provide a new criterion, not only for establishing the diagnosis of liposarcoma, but also for differentiating confusing histologic types of liposarcoma and these lesions from other types of sarcomas.

Aged

Liposarcoma of the neck: a clinicopathologic study of 4 cases.

A clinicopathological study of 4 patients with liposarcoma in the neck treated surgically is presented. Three of the liposarcomas were located in the supraclavicular region, two to the right one to the left, and one appeared to the left in the back of the neck. Liposarcoma rarely involves the head and neck region. A survey is given of the few reported liposarcomas in this region. Two of the tumors in the present series were well differentiated, one of which recurred repeatedly. The other two tumors were round-cell and pleomorphic in type, both of which recurred. At the end of follow-up 11 and 9 years, the two patients with well-differentiated liposarcomas were alive. The other two patients had died after 5 and 4 years from intercurrent disease and metastatic spread, respectively. The histopathological basis for the diagnosis, distinguishing features of intramuscular (infiltrating) lipoma, hibernoma and spindle cell lipoma, as well as the treatment, are discussed.

Adult

Liposarcoma of the oropharyngeal region. Review of the literature and report of two cases.

Liposarcomas of the oropharyngeal regions are exceedingly rare. Their silent, slow growth, submucosal or deep location, circumscription, and firm but resilient texture often suggest a diagnosis of a cyst or benign soft-tissue neoplasm. Two cases of well-differentiated myxoid liposarcoma are presented. The literature of over half a century was reviewed, and all documented cases were critically analyzed. The clinical data correlated with the histopathology and biologic behavior of the tumors indicated that two thirds of all liposarcomas of the head and neck are of the myxoid type. The well-differentiated myxoid liposarcoma was the most common one and has an over-all favorable prognosis. Lipomas of the oropharyngeal regions are relatively common and small, generally not exceeding 2.5 cm. in greatest diamter. A lobulated firm tumor of fast tissue significantly exceeding this size should be strongly suspected of being a liposarcoma.

Adult

Chromosome abnormalities in liposarcomas.

We performed a cytogenetic study of short-term cultures from fresh surgical specimens obtained from four patients with liposarcoma. Myxoid liposarcomas (cases 1-3) were associated with a specific translocation between chromosomes 12 and 16. Trisomy 8, a nonrandom secondary aberration in myxoid liposarcoma, was observed in the third case as the only additional change. Round cell liposarcoma (case 4) showed complex chromosomal aberrations affecting chromosomes 1, 2, 5, 6, 7, 13, 14, 17, 19, and 22. Neither band 12q13 nor 16p11 was visibly rearranged. Three subgroups of liposarcomas are proposed. The first group is characterized by t(12;16)(q13;p11), the second group by ring chromosomes, telomeric associations, and giant markers, and the last by complex numerical and structural aberrations.

Adult

Well-differentiated liposarcoma (atypical lipoma) of deep soft tissue of the extremities, retroperitoneum, and miscellaneous sites. A follow-up study of 92 cases with analysis of the incidence of "dedifferentiation".

Ninety-two cases of well-differentiated liposarcoma of deep soft tissue of the extremity, retroperitoneum, and groin with follow-up information of at least 2 years and no evidence of dedifferentiation at the time of diagnosis were studied to determine their long-term behavior. The tumors occurred most commonly in the muscles of the extremity (46 cases), followed by the retroperitoneum (23 cases), groin (14 cases), and miscellaneous sites (nine cases). Tumors in the retroperitoneum recurred in nearly all cases (21 of 23 cases), occasionally caused patient death, and dedifferentiated in four cases (median time to dedifferentiation, 8 years). Tumors in the groin had a similar high recurrence rate (11 of 14 cases), caused death of patients (two of 14 cases), and dedifferentiated (four of 14 cases). In contrast, those in the extremity recurred less frequently (20 of 46 cases) and had no disease-related mortality. Three of 46, however, underwent dedifferentiation (median time to dedifferentiation, 7 years). Of the 11 cases that underwent dedifferentiation, the interval between diagnosis and dedifferentiation ranged from 2 to 18 years (median time, 9 years; average time, 11 years). Six of the 11 patients showed dedifferentiated foci in the first recurrence, and three died of metastatic disease. Our study indicates that the behavior of well-differentiated liposarcomas is strongly influenced by location. Although the prevailing view is that dedifferentiation is restricted to tumors of the retroperitoneum, our study indicates that it is not a site-specific phenomenon, but is more likely a time-dependent phenomenon seen in situations with a high likelihood for clinical persistence of disease for a long period. Dedifferentiation identifies a tumor that is potentially more aggressive; yet the progression of the disease following dedifferentiation may be highly variable and probably depends on a number of factors, including the amount of dedifferentiation and type of therapy. Although atypical lipoma is an acceptable term for well-differentiated liposarcomas of the subcutis, it fails to convey the potentially life-threatening properties of retroperitoneal tumors. For these lesions as well as those in the deep soft tissues of the extremity, retention of the term well-differentiated liposarcoma is advocated.

Adult

Liposarcoma of the larynx: a multicentric or a metastatic malignancy.

The third case of liposarcoma of the larynx, this one arising from the preepiglottic space, is presented. The report is unique in so far as the patient previously had been treated for a liposarcoma in another anatomic region. The diagnosis in this case was in doubt until electron microscopic studies were done. Since the histopathology of the laryngeal and the previous liposarcoma were different, the question of metastasis versus multicentricity was raised. Other discussions of liposarcomas over the past three decades have not resolved this aspect of their behavior completely. In this instance, after considering avenues of metastatic spread in conjuction with the histopathology, it would appear that the laryngeal lesion was a second primary and not a metastasis.

Aged

[A case of mediastinal liposarcoma].

Primary liposarcomas of the mediastinum are rare neoplasms comprising only 0.13-0.75% of mediastinal tumors. We report a case of liposarcoma arising in the right posterior mediastinum. A 74-year-old man without symptoms was admitted to our hospital for evaluation of an abnormal shadow on chest roentgenogram. Computed tomogram (CT) and magnetic resonance (MR) imaging revealed a mediastinal tumor. The tumor was surgically removed, and the diagnosis of well-differentiated liposarcoma was established. MR imaging was superior to CT in evaluation of tumor extent, but not in differential diagnosis as liposarcoma or lipoma.

Aged

[Liposarcoma of the transverse mesocolon--a case report].

Primary mesenteric liposarcoma is a rare neoplasm. We experienced a case of liposarcoma of transverse mesocolon. In our case, the examination of ultrasonography and CT scan revealed the tumor was solid and encapsulated. Preoperatively we suspected the tumor was malignant by the angiographic findings. Laparotomy revealed that the tumor was located in the transverse mesocolon and it could be removed easily. The histopathological diagnosis was myxoid type liposarcoma. It is said generally that liposarcoma is liable to recur after simple resection, therefore, we reconsider that we should have excised more extensively for this case. The patient is doing well without evidence of recurrence for 17 months after operation.

Aged

Primary round cell liposarcoma of the omentum. A case report.

Liposarcomas are the most common of the malignant soft tissue tumors arising in the mediastinum and retroperitoneum. We have treated patients for round cell liposarcoma, an unusual histologic subtype, which is reported to be histologically mistaken for Ewing's sarcoma, lymphoma and other round cell neoplasms. The successful resection of a 2,300-g round cell liposarcoma of the omentum was recently performed at our hospital. Ultrastructural observations of this tumor are characterized by massive proliferation of the mitochondria in addition to the presence of lipid vacuoles in tumor cells. To our knowledge, no description of substantial mitochondrial proliferation in round cell liposarcoma has appeared previously in the literature; therefore, this is the first case report of histopathologic, cytopathologic and electron microscopic observations on this extremely rare tumor.

Female

Electron microscopy of adipose tissue tumors: comparative features of hibernomas, myxoid and pleomorphic liposarcomas.

Two hibernomas, 16 myxoid, and eight pleomorphic liposarcomas were studied by transmission electron microscopy. Neoplastic cells in hibernomas and the type I cells--adipocytes--in myxoid liposarcomas consistently display abundant lipid droplet populations and prominent basal lamina deposition. Despite some variability in their distribution, these features clearly pertain to the mature and/or maturing characteristics of brown and white adipose cells. On the other hand, the more primitive type II cells of myxoid liposarcomas display highly variable, and occasionally absent, lipid droplet populations and basal lamina deposition. Moreover, the type II cells may also display other features such as prominent cytoplasmic filaments and rough endoplasmic reticulum that, while not characteristic of typical adipose cells, are still consistent with the more primitive mesenchymal cells from which they are assumed to derive. The cells of pleomorphic liposarcomas exhibit a variable lipid droplet population and apparently total absence of basal lamina deposition. Moreover, they often display atypical cell junctions that are neither characteristic for adipose cells nor for the "primitive reticular cells" from which adipocytes presumably derive. These observations would suggest that some "high grade" sarcomas may no be truly "undifferentiated"; rather, they may often display structural characteristics indicative of multiple as well as variable lines of differentiation. Therefore, classifications of such tumors based on quantitatively limited observations may not truly reflect their evident complexities.

Adipose Tissue

Pleomorphic Liposarcoma: Comprehensive Genomic Analysis of 39 Cases With Comparison to Other Genomically Complex Sarcomas.

Pleomorphic liposarcoma (PLPS) is an aggressive high-grade sarcoma that often shows diverse morphological features and can mimic high-grade undifferentiated pleomorphic sarcoma (UPS)/spindle cell sarcoma or myxofibrosarcoma (MFS), especially when pleomorphic lipoblasts are sparse. The molecular profile of PLPS is distinct from well differentiated/dedifferentiated liposarcoma and myxoid liposarcoma. In this study, we investigate 39 cases of PLPS by comprehensive genomic profiling, occurring in 32 patients with available molecular data. Cases were reviewed and morphologic parameters-lipoblastic component, UPS-like, and MFS-like areas were estimated. The genomic findings were collected and compared to UPS and MFS groups studied using the same platform. The cohort included 15 females and 17 males, with a median age of 56.5 (range, 34-78). The lower extremity (n = 17) was the most common site involved, followed by upper extremity (n = 5) and pelvis (n = 5). UPS-like and MFS-like patterns were the most common morphologic variants, ranging from 15% to 95% and 20% to 90%, respectively. TP53 (87%) and RB1 (51%) mutations and copy number alterations were the most common alterations seen, followed by ATRX (36%). Compared to UPS and MFS, TP53 and RB1 gene alterations were significantly more common in PLPS. Conversely, CDKN2A/B deletions were infrequent in PLPS. Survival analysis showed that MYC amplification was associated with significantly shorter overall survival in PLPS. Among histologic variants, CYSLTR2 alterations were found to be highest in cases with predominantly pleomorphic lipoblasts; additionally, strong correlations were found between gene alteration frequencies of MFS and MFS-like PLPS, and between UPS and UPS-like PLPS. RB1 allele-specific copy number analysis showed loss of heterozygosity in 82% of cases. Our cohort of PLPS showed a complex molecular landscape with distinct genetic alterations, histologic correlations, and clinical outcomes, highlighting its unique position among genomically complex sarcomas and providing insights that may inform future diagnostic and therapeutic approaches.

Humans

Non-epithelial tumors of the nasal cavity, paranasal sinuses and nasopharynx: a clinicopathologyic study. VIII. Adipose tissue tumors (lipoma and liposarcoma).

In a study of 256 non-epithelial neoplasms involving the nasal cavity, paranasal sinuses and nasopharynx, only two lesions were classified as adipose tissue tumors (one lipoma and one liposarcoma). The lipoma was found incidentally when tissue removed from the maxillary sinus was studied histologically, the patient having been treated with a Caldwell-Luc procedure for maxillary sinusitis. The liposarcoma produced a large mass involving the nasal cavity, maxillary sinus, ethmoid area, hard palate and maxillary, temporal and sphenoid bones. The tumor extended into the cranial cavity and eventually led to the patient's death. The problems involved in histologically differentiating liposarcomas from other lesions are discussed. Even though adipose tissue tumors are among the most common soft tissue neoplasms, these lesions rarely occur in the nasal cavity, paranasal sinuses and nasopharynx.

Adult

Liposarcomas of the head and neck: a review of the literature and addition of four cases.

Liposarcomas of the head and neck are rare. There have been 25 previously reported patients in the literature. Four patients with head and neck liposarcomas, recently treated by the Head and Neck Surgery Service, Walter Reed Army Medical Center, are presented. Less than half of reported patients were noted to be living without evidence of disease. Prognosis generally corresponds to the cell type of the tumor. Intraoral, cheek and orbital tumors seem to have a worse prognosis compared to neck tumors. Wide local excision remains the treatment of choice. Advances in surgical techniques have allowed adequate therapy for most head and neck liposarcomas. Advanced lesions should be managed by conservative surgery and radical radiation therapy.

Adolescent

Liposarcoma of the breast. Case report and review of the literature.

A case of primary liposarcoma of the breast in a 65-years-old woman is described by light- and electron microscopy. The patient had previously had a cystosarcoma phyllodes removed from the same area. A review of the literature showed 34 previously published cases of liposarcoma of the breast, which regarding age distribution, histological type and pattern of metastasis corresponded to liposarcomas of the lower limbs.

Aged

Trisomy 8 as a nonrandom secondary change in myxoid liposarcoma.

We report the cytogenetic findings in 5 cases of myxoid liposarcoma following short-term culture. In all 5 tumors a t(12:16)(q13:p11), characteristic of the myxoid form of liposarcoma, was observed. Trisomy 8 was present in two tumors as the only additional change and in a third in addition to other abnormalities. In the other two tumors the t(12:16) was present as the sole change. Three other myxoid liposarcomas with trisomy 8 as an additional aberration have been reported, suggesting that it could represent a non-random secondary event in these tumors.

Adult