Liposarcoma of the extremities: MR imaging features and their correlation with pathologic data.

OBJECTIVE: To describe the MRI features of liposarcomas of the extremities and correlate them with data from the histologic subtypes. MATERIAL AND METHODS: Retrospective study of 20 cases of liposarcoma of the extremities identified on MRI, surgically removed and confirmed at pathology. On MRI examination, T1- and T2-weighted fat-suppressed and non-fat-suppressed images were acquired then gadolinium-enhanced fat-suppressed T1-weighted images were obtained in at least two orthogonal planes. RESULTS: Sixteen female and four male patients aged 12 to 77 years old at presentation, in 16 cases, with a slowly enlarging painless mass (demonstrating no associated local or general inflammatory components), located in the lower extremity (16 cases) and predominantly located in the thigh (13 cases). Pathologic examination revealed three cases of well-differentiated liposarcoma, 12 cases of myxoid liposarcoma one of which with round cells, three cases of pleomorphic liposarcoma, one case of dedifferentiated liposarcoma and one case of mixed-type liposarcoma. MR images mostly showed well-circumscribed tumors (19 cases) . Well-differentiated liposarcomas typically demonstrated a very specific diagnostic appearance as a predominantly adipose mass containing nonlipomatous components seen as thick septa that may show nodularity. Other subtypes of liposarcoma demonstrated a small amount of adipose tissue thus producing a marbled textural pattern on T1-weighted images particularly in myxoid liposarcomas (9 cases), or even nonlipomatous elements in high-grade liposarcomas (in round cell liposarcoma and in two out of three pleomorphic liposarcomas). The myxoid subtype has also a relatively characteristic appearance as a low signal intensity noted on T1-weighted images and a marked high signal intensity on T2. The dedifferentiated liposarcoma has a very specific radiologic appearance as a nonlipomatous component within a predominantly adipose mass, simulating that of well-differentiated liposarcomas. CONCLUSION: MRI of extremity liposarcomas is a highly reliable and sensitive method to characterize liposarcomas. Besides its value in the diagnosis of liposarcoma and locoregional extension control, it allows proper identification of the specific histologic subtypes of liposarcoma. LEVEL OF EVIDENCE: Level IV. Rétrospective diagnostic study.

Acute disseminated encephalomyelitis following herpes simplex encephalitis.

Acute disseminated encephalomyelitis is an acute immunomediated demyelinating disorder of the central nervous system, usually encountered in children or adolescents and characterized by multifocal neurologic deficits of rapid onset. It is often preceded by various infectious diseases or vaccination, but acute disseminated encephalomyelitis developing after herpes simplex encephalitis is rare. We report such a case in a 2-year-old girl which illustrates the importance of MRI features to consider acute disseminated encephalomyelitis in a patient who develops neurologic signs after the onset of HVS encephalitis.

Chemical characterization of Titan's tholins: solubility, morphology and molecular structure revisited.

In this work Titan's atmospheric chemistry is simulated using a capacitively coupled plasma radio frequency discharge in a N(2)-CH(4) stationnary flux. Samples of Titan's tholins are produced in gaseous mixtures containing either 2 or 10% methane before the plasma discharge, covering the methane concentration range measured in Titan's atmosphere. We study their solubility and associated morphology, their infrared spectroscopy signature and the mass distribution of the soluble fraction by mass spectrometry. An important result is to highlight that the previous Titan's tholin solubility studies are inappropriate to fully characterize such a heterogeneous organic matter and we develop a new protocol to evaluate quantitatively tholins solubility. We find that tholins contain up to 35% in mass of molecules soluble in methanol, attached to a hardly insoluble fraction. Methanol is then chosen as a discriminating solvent to characterize the differences between soluble and insoluble species constituting the bulk tholins. No significant morphological change of shape or surface feature is derived from scanning electron microscopy after the extraction of the soluble fraction. This observation suggests a solid structure despite an important porosity of the grains. Infrared spectroscopy is recorded for both fractions. The IR spectra of the bulk, soluble, and insoluble tholins fractions are found to be very similar and reveal identical chemical signatures of nitrogen bearing functions and aliphatic groups. This result confirms that the chemical information collected when analyzing only the soluble fraction provides a valuable insight representative of the bulk material. The soluble fraction is ionized with an atmospheric pressure photoionization source and analyzed by a hybrid mass spectrometer. The congested mass spectra with one peak at every mass unit between 50 and 800 u confirm that the soluble fraction contains a complex mixture of organic molecules. The broad distribution, however, exhibits a regular pattern of mass clusters. Tandem collision induced dissociation analysis is performed in the negative ion mode to retrieve structural information. It reveals that (i) the molecules are ended by methyl, amine and cyanide groups, (ii) a 27 u neutral moiety (most probably HCN) is often released in the fragmentation of tholin anions, and (iii) an ubiquitous ionic fragment at m/z 66 is found in all tandem spectra. A tentative structure is proposed for this negative ion.

Hydatid cyst of the breast: a case report.

Echinococcal involvement of the breast is extremely rare, even in the endemic countries. We report the case of a 31-year-old woman who presented with a 5 cm mammary mass. Mammography and sonography showed a well-circumscribed cystic lesion. Diagnosis of hydatid cyst was confirmed by pathological examination.

[Cerebral hydatid disease: imaging features]. / Hydatidose cérébrale: aspects en imagerie.

Cerebral hytatid cysts (HC) are extremely rare, forming 2% of all intra cranial space occupying lesions even in counties where the disease is endemic. HC diagnosis is usually based on a pathognomonic computed tomography (CT) pattern. In order to assess the value of MR we reviewed the CT (n=25) and magnetic resonance (MR, n=4 including diffusion and proton magnetic resonance spectroscopy in 1) imaging of 25 patients with pathologically confirmed cerebral hydatid disease. 19 HC were seen in children under 16 years. All were supra tentorial with 22 in the middle cerebral artery territory. HC was solitary in 18 cases, unilocular in 23 and multi-vesicular in 2 with heavily calcified pericyst in 1. 2 cysts were intra ventricular and 1 intra aqueducal. The most typical features were well defined, smooth thin walled spherical or oval cystic lesions of CSF density and/or signal with considerable mass effect (20/25). Surrounding oedema with complete or incomplete rim enhancement was seen in 3 cases which were labelled as complicated and/or infected cysts. Although CT is diagnostic of hydatid disease in almost all cases (22/25), MRI including diffusion and spectroscopy precisely demonstrate location, number, cyst capsule, type of signal and enhancement and allows diagnosis of atypical or complicated HC and appears more helpful in surgical planning.

[Esophageal mucocele: report of 2 pediatric cases]. / Mucocèle oesophagienne à propos de deux observations pédiatriques.

Two cases of esophageal mucocele in pediatric patients are reported: two children of 5 and 9 years respectively underwent surgical isolation of the esophagus and esophagocoloplasty for caustic stenosis related to accidental ingestion of caustic soda. Clinical pattern of mediastinal compression was proved with cervical fistulous tract in one case. In both cases, thoracic computed tomography was a sensitive imaging method to demonstrate the mucocele and its extension. Esophageal mucocele is rarely described in children, especially following esophageal corrosive stricture.