Well-differentiated liposarcoma of the retroperitoneum with a fat-fluid level: US, CT, and MR appearance

Traumatic Extra-capsular and Intra-capsular Floating Fat: Fat-fluid Levels of the Knee Revisited

Floating fat is a sign of acute bone injury at the knee following trauma. The goal of this article is to review the etiology, patterns, and mimickers of extra-capsular and intra-capsular floating fat, with the major emphasis on knee trauma in the acute setting. We will discuss the spectrum of multimodal imaging findings for rare presentations of extra-capsular floating fat, and contrast these with common and atypical forms of intra-capsular lipohemarthrosis, as an aid to the assessment of acute bone trauma at the knee.

Giant liposarcoma of the omentum mimicking an ovarian tumor. A case report

Liposarcomas are common soft tissue of the retroperitoneum and the limbs. They are rarely found in the greater omentum. Once in the peritoneum, these can become enormous and can be mistaken for ovarian mass. The authors report a case of giant omental liposarcoma revealed by an abdominal mass and genital prolapse due to the compression syndrome. A complete macroscopic resection of the omental tumour was performed. A post operative chemotherapy was also prescribed. A description of this clinical presentation in the preoperative assessment, the characteristics of this tumour, together with the use of adjuvant chemotherapy are discussed in this report.

Imaging of the retroperitoneum

The retroperitoneum is the compartmentalized space bounded anteriorly by the posterior parietal peritoneum and posteriorly by the transversalis fascia. It extends from the diaphragm superiorly to the pelvic brim inferiorly. This article discusses clinically relevant anatomy of the abdominal retroperitoneal spaces, their cross-sectional imaging evaluation with computed tomography and magnetic resonance imaging, and the imaging features of common retroperitoneal pathologic processes.

Diagnosis and triage of a patient with an extra-osseous fat fluid level

Extra-osseous fat fluid level is rarely seen in osteomyelitis, with only three magnetic resonance imaging (MRI) cases previously reported in the literature. The rarity of this finding is probably secondary to the extensive necrosis of bone marrow that needs to occur at a rapid phase for the fat to accumulate. However, an extra-osseous fat fluid level is a specific diagnostic sign of osteomyelitis in cases with otherwise equivocal imaging findings and should be reported as such, especially when associated with medullary bone destruction and in the absence of trauma.

The differential imaging features of fat-containing tumors in the peritoneal cavity and retroperitoneum: the radiologic-pathologic correlation

There are a variety of fat-containing lesions that can arise in the intraperitoneal cavity and retroperitoneal space. Some of these fat-containing lesions, such as liposarcoma and retroperitoneal teratoma, have to be resected, although resection can be deferred for others, such as adrenal adenoma, myelolipoma, angiomyolipoma, ovarian teratoma, and lipoma, until the lesions become large or symptomatic. The third group tumors (i.e., mesenteric panniculitis and pseudolipoma of Glisson's capsule) require medical treatment or no treatment at all. Identifying factors such as whether the fat is macroscopic or microscopic within the lesion, the origin of the lesions, and the presence of combined calcification is important for narrowing the differential diagnosis. The development and wide-spread use of modern imaging modalities make identification of these factors easier so narrowing the differential diagnosis is possible. At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques. Thus, the questions about the treatment methods have become increasingly important. Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.

Prevalence and diagnostic significance of fluid–fluid levels in soft-tissue neoplasms

AIM

To report the prevalence of fluid-fluid levels (FFLs) in soft-tissue tumours as demonstrated by magnetic resonance imaging (MRI) and the potential diagnostic relevance of this finding.

MATERIALS AND METHODS

A retrospective analysis was performed of 726 consecutive patients (361 women, 365 men, mean age 47.6 years+/-20.1 SD) presenting with a soft-tissue mass over a 7-year period. All subjects underwent MRI and final diagnosis was based on biopsy/surgical resection, or clinical follow-up and characteristic imaging findings. The patients were divided according to the presence or absence of FFLs on T2-weighted (T2W) axial MRI and histological diagnosis (non-neoplastic, neoplastic benign, neoplastic malignant). Cases with FFLs were sub-categorized depending upon the proportion of tumour containing FFLs: <1/3, 1/3-2/3 and >2/3, in order to determine whether the proportion of FFLs was useful for differential diagnosis.

RESULTS

Twenty-four of the 726 (3.3%: confidence interval 2.1-4.9%) soft-tissue masses contained FFLs. One of the 24 (4.1%) was non-neoplastic (one ganglion), 12 (50.0%) were benign neoplasms (nine haemangiomas, two schwannomas, one hamartoma) and 11 (45.9%) were malignant neoplasms (one leiomyosarcoma, one liposarcoma, one malignant fibrous histocytoma, one mxyofibrosarcoma, two primitive neuroectodermal tumours, two synovial sarcomas, one spindle cell sarcoma, and two sarcomas not otherwise specified). The presence of FFLs did not help to differentiate benign from malignant neoplasms. Of the 12 benign neoplasms, 66.7% contained over two-thirds FFLs, the majority of which were haemangiomas. Of the 10 malignant neoplasms, all contained less than two-thirds FFLs: 20% had less than one-third, 80% had one to two-thirds FFLs.

CONCLUSIONS

The prevalence of FFLs in soft-tissue tumours referred to a specialist orthopaedic oncology unit is 3.3%. However, the presence of FFLs does not reliably distinguish benign from malignant neoplasms, although all lesions with more than two-thirds FFLs were benign.

Mucinous adenocarcinoma arising from one retroperitoneal mature cystic teratoma in a postmenopausal woman*

Malignant degeneration of a retroperitoneal mature cystic teratoma to adenocarcinoma at postmenopausal age is extremely rare. A 72-year-old woman with mucinous adenocarcinoma arising from a retroperitoneal mature cystic teratoma is presented.