Field dipolarization in Saturn's magnetotail with planetward ion flows and energetic particle flow bursts: Evidence of quasi-steady reconnection.

We present a case study of an event from 20 August (day 232) of 2006, when the Cassini spacecraft was sampling the region near 32 RS and 22 h LT in Saturn's magnetotail. Cassini observed a strong northward-to-southward turning of the magnetic field, which is interpreted as the signature of dipolarization of the field as seen by the spacecraft planetward of the reconnection X line. This event was accompanied by very rapid (up to ~1500 km s-1) thermal plasma flow toward the planet. At energies above 28 keV, energetic hydrogen and oxygen ion flow bursts were observed to stream planetward from a reconnection site downtail of the spacecraft. Meanwhile, a strong field-aligned beam of energetic hydrogen was also observed to stream tailward, likely from an ionospheric source. Saturn kilometric radiation emissions were stimulated shortly after the observation of the dipolarization. We discuss the field, plasma, energetic particle, and radio observations in the context of the impact this reconnection event had on global magnetospheric dynamics.

Surface current balance and thermoelectric whistler wings at airless astrophysical bodies: Cassini at Rhea.

Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocity and magnetic field have an intrinsic difficulty modeling the plasma absorber's sharp surface. We overcome this problem by instead using integral equations to solve for ion and electron currents and obtain agreement with the magnetic perturbations at Rhea's flux tube edge. An analysis of the plasma dispersion relations and Cassini data reveals that field-guided whistler waves initiated by (1) the electron velocity anisotropy in the flux tube and (2) interaction with surface sheath electrostatic waves on topographic scales may facilitate propagation of the current system to large distances from Rhea. Current systems like those at Rhea should occur generally, for plasma absorbers of any size such as spacecraft or planetary bodies, in a wide range of space plasma environments. Motion through the plasma is not essential since the current system is thermodynamic in origin, excited by heat flow into the object. The requirements are a difference of ion and electron gyroradii and a sharp surface, i.e., without a significant thick atmosphere. KEY POINTS: Surface current balance condition yields a current system at astronomical bodiesCurrent system possible for sharp (airless) objects of any sizeCurrent system is thermoelectric and motion through the plasma nonessential.

Detection of a strongly negative surface potential at Saturn's moon Hyperion.

On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (∼ -200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator.

The dust halo of Saturn's largest icy moon, Rhea.

Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.

Identification of a dynamic atmosphere at Enceladus with the Cassini magnetometer.

The Cassini magnetometer has detected the interaction of the magnetospheric plasma of Saturn with an atmospheric plume at the icy moon Enceladus. This unanticipated finding, made on a distant flyby, was subsequently confirmed during two follow-on flybys, one very close to Enceladus. The magnetometer data are consistent with local outgassing activity via a plume from the surface of the moon near its south pole, as confirmed by other Cassini instruments.

Anti-planetward auroral electron beams at Saturn.

Strong discrete aurorae on Earth are excited by electrons, which are accelerated along magnetic field lines towards the planet. Surprisingly, electrons accelerated in the opposite direction have been recently observed. The mechanisms and significance of this anti-earthward acceleration are highly uncertain because only earthward acceleration was traditionally considered, and observations remain limited. It is also unclear whether upward acceleration of the electrons is a necessary part of the auroral process or simply a special feature of Earth's complex space environment. Here we report anti-planetward acceleration of electron beams in Saturn's magnetosphere along field lines that statistically map into regions of aurora. The energy spectrum of these beams is qualitatively similar to the ones observed at Earth, and the energy fluxes in the observed beams are comparable with the energies required to excite Saturn's aurora. These beams, along with the observations at Earth and the barely understood electron beams in Jupiter's magnetosphere, demonstrate that anti-planetward acceleration is a universal feature of aurorae. The energy contained in the beams shows that upward acceleration is an essential part of the overall auroral process.

Cassini magnetometer observations during Saturn orbit insertion.

Cassini's successful orbit insertion has provided the first examination of Saturn's magnetosphere in 23 years, revealing a dynamic plasma and magnetic environment on short and long time scales. There has been no noticeable change in the internal magnetic field, either in its strength or its near-alignment with the rotation axis. However, the external magnetic field is different compared with past spacecraft observations. The current sheet within the magnetosphere is thinner and more extended, and we observed small diamagnetic cavities and ion cyclotron waves of types that were not reported before.

Aspiration cytology of pediatric solitary papillary hyperplastic thyroid nodule.

CONTEXT: Solitary papillary hyperplastic thyroid nodules (SPHTNs) are frequently encountered in children and teenagers. Although the histologic features are well described, to the best of our knowledge, cytologic findings have not been reported. OBJECTIVES: To review the cytologic features of histologically proven SPHTNs and to identify the potential diagnostic pitfalls in cytologic diagnosis. MATERIALS AND METHODS: Fine-needle aspiration cytology of 3 histologically proven SPHTNs was reviewed. RESULTS: Two girls and 1 boy (ages 11, 12, and 15 years) were affected. The cytologic diagnosis in all 3 cases was suspicious for papillary thyroid carcinoma (PTC). The spectrum of cytologic findings included broad flat sheets and 3-dimensional clusters with fire flares. There was mild to moderate nuclear pleomorphism and nuclear atypia. Short nonbranching papillae with transgressing vessels shown to represent hyperplastic papillae on histologic sections were identified in all cases. The background contained giant cells, histiocytes, and watery and inspissated colloid. Although nuclear grooves were identified in occasional cells, intranuclear inclusions were absent. A cell block section (1 case) and histologic sections of SPHTNs (2 cases) were immunohistochemically negative for cytokeratin 19. CONCLUSIONS: Fine-needle aspiration of SPHTNs may be difficult to interpret accurately and can result in false-positive diagnosis of PTC. Although it shares several cytologic features with PTC, the presence of fire flares and short nonbranching papillae, as well as lack of intranuclear inclusions and watery and inspissated colloid in SPHTN appear to be useful features that are helpful in distinguishing SPHTN from PTC. Negative immunohistochemical staining for cytokeratin 19 is useful in excluding a diagnosis of PTC.

Diagnosing primary and metastatic renal cell carcinoma: the use of the monoclonal antibody 'Renal Cell Carcinoma Marker'.

The diagnosis of primary or metastatic renal cell carcinoma (RCC) can be difficult, especially in small biopsies, because of the wide variety of histologic appearances and clinical presentations that RCC can assume. An immunomarker specific for RCC is currently not available. We tested the relevant diagnostic use of the Renal Cell Carcinoma Marker (RCC Ma), a monoclonal antibody, against a normal human proximal tubular brush border antigen. Immunostaining using RCC Ma and the avidin-biotin-peroxidase complex technique was performed on archival tissues from primary and metastatic tumors of renal or nonrenal origin. A total of 122 of 153 primary RCCs (79.7%) were positive [clear cell (84%), papillary (96%), chromophobe (45%), sarcomatoid (25%), and collecting duct (0%)], with > or =10% of tumor cells stained in 93% of cases. None of the 64 primary renal tumors other than RCC, including 15 oncocytomas, was positive. Fifteen of 146 (10.2%) nonrenal primary tumors were positive (5 of 17 breast tumors, 8 of 8 parathyroid adenomas, and 2 of 7 embryonal carcinomas). Forty-two of 63 (67%) metastatic RCCs were positive with > or =10% of cells being stained in 83% of them. Two of 108 (2%) metastases from tumors other than RCCs were positive, both of which were metastatic breast carcinomas; however, only 10% (2 of 19) of metastatic breast carcinomas were positive. RCC Ma is an excellent marker for primary RCC, which should facilitate its diagnosis in a small biopsy. Although RCC Ma remains highly specific (98%) for metastatic RCC, a negative result may not rule out metastatic RCC because of a rather low sensitivity and a focal staining pattern in some of the positive cases. RCC Ma may also facilitate the differential diagnosis between oncocytoma and other types of RCC when they are composed mostly of eosinophilic cells.

The role of fine-needle aspiration biopsy in the diagnosis and management of juvenile hemangioma of the parotid gland and cheek.

BACKGROUND: The current recommendation for the management of juvenile hemangiomas (JH) is to delay treatment in the hope of spontaneous regression. However, accurate diagnosis is necessary before considering conservative management. Traditionally, the diagnosis of JH has required excisional biopsy. The cytology literature on this relatively rare neoplasm is sparse. OBJECTIVE: To present our experience with fine-needle aspiration in the diagnosis and management of JH. DESIGN: Three cases with a cytologic diagnosis consistent with JH of the parotid gland and cheek were identified from our cytopathology files. Aspirate smears, immunohistochemical studies, computed tomographic scan findings, and clinical follow-up were reviewed. RESULTS: Patients were female infants ranging in age from 3 to 9 months and presented with an oval firm mass (size range, 2.0-5.0 cm) involving the parotid gland (2 cases) and cheek (1 case). Computed tomographic scan with contrast demonstrated homogeneous enhancement. Aspirate smears revealed spindle-shaped cells in sheets and clusters in a background of blood. The parotid gland aspirates and cell block preparations revealed ductal structures entrapped in sheets of spindle-shaped cells. Immunohistochemical studies revealed prominent vascular spaces lined by CD34 and factor VIII-positive flattened endothelial cells. The diagnosis of JH was rendered on the basis of the cytologic findings in conjunction with the radiologic and clinical findings. On clinical follow-up (8-24 months), none of the patients has shown any progression of the lesion. CONCLUSIONS: Fine-needle aspiration, in conjunction with imaging studies, is a useful tool in the diagnosis and management of JH. It eliminates the need for surgical excision for diagnostic purposes and allows for clinical follow-up of patients with JH.

Diagnostic utility of intracytoplasmic lumen and transgressing vessels in evaluation of Hürthle cell lesions by fine-needle aspiration.

INTRODUCTION: Recent abstracts have emphasized the importance of recognizing intracytoplasmic lumen and transgressing vessels as useful criteria enabling distinction between Hürthle cells encountered in neoplastic and nonneoplastic thyroid aspirates. The purpose of this retrospective study was to evaluate if application of these criteria improves specificity and sensitivity of cytologic diagnosis of true Hürthle cell neoplasms. MATERIALS AND METHODS: We retrospectively reviewed 30 fine-needle aspirates of thyroid with cytologic diagnosis of Hürthle cell neoplasms (13 cases) and nonneoplastic thyroid with prominent Hürthle cells (17 cases). All cases were evaluated for the presence of intracytoplasmic lumen and transgressing vessels and were reclassified as neoplastic or nonneoplastic based on the presence or absence of 1 or both of these criteria. Surgical follow-up was available in all cases. RESULTS: Surgical follow-up in 13 cases of Hürthle cell neoplasms revealed Hürthle cell carcinoma (3 cases), Hürthle cell adenoma (6 cases), and Hashimoto's thyroiditis (4 cases). Seventeen cases with nonneoplastic diagnosis revealed Hürthle cell carcinoma (1 case), Hashimoto's thyroiditis (12 cases), and nodular goiter (4 cases). After application of the previously mentioned cytologic criteria, the cytologic diagnoses were reclassified as Hürthle cell neoplasms (13 cases) and nonneoplastic thyroid (17 cases). The true sensitivity of the test before and after the application of the criteria was 90% and 100%, respectively. The true specificity before and after the application of the cytologic criteria was 65% and 85%, respectively. CONCLUSIONS: Intracytoplasmic lumen and transgressing vessels are helpful features in distinguishing neoplastic and nonneoplastic Hürthle cell thyroid lesions. Use of these criteria may improve the specificity and sensitivity of the cytologic diagnosis.

Oestrogen receptor expression in normal breast epithelium.

Higher levels of oestrogen receptor (ER) expression in normal breast epithelium may compound the increase in breast cancer risk seen with prolonged estrogen exposure. In prior studies, we have used immunohistochemical ER assays on fresh frozen samples of benign breast tissue. Future studies will be more feasible on paraffin-embedded samples, and newer, more sensitive antibodies are now available. We examined 30 samples of paraffin-embedded breast epithelium from postmenopausal women with two antibodies, 6F11 and TE111. We find that the median labelling indices for ER are significantly higher using these antibodies, compared with previous results. The threshold for ER positivity will, therefore, have to be reset in future studies, since there are still many issues that remain to be resolved in this area.

Galileo magnetometer measurements: a stronger case for a subsurface ocean at Europa.

On 3 January 2000, the Galileo spacecraft passed close to Europa when it was located far south of Jupiter's magnetic equator in a region where the radial component of the magnetospheric magnetic field points inward toward Jupiter. This pass with a previously unexamined orientation of the external forcing field distinguished between an induced and a permanent magnetic dipole moment model of Europa's internal field. The Galileo magnetometer measured changes in the magnetic field predicted if a current-carrying outer shell, such as a planet-scale liquid ocean, is present beneath the icy surface. The evidence that Europa's field varies temporally strengthens the argument that a liquid ocean exists beneath the present-day surface.

Is repeated fine-needle aspiration cytology useful in the management of patients with benign nodular thyroid disease?

Management of nonneoplastic thyroid nodules (TN) diagnosed by fine-needle aspiration (FNA) is controversial. While clinical follow-up with repeat FNA for enlarging TN is recommended in some studies, others recommend repeat FNA in follow-up of all benign TN after several months or years, in order to identify possible misdiagnosed malignant lesions. This study was done to determine the usefulness of repeat FNA in patients with benign nodular thyroid disease. We studied 94 fine-needle reaspirations performed on 43 females and 2 males 48.2 +/- 17 years of age with benign nodular thyroid nodular disease. Four patients had 3 consecutive FNAs and 41 patients had 2 consecutive FNAs. All FNAs were carried out by the same endocrinologist in the same thyroid area or by cytopathologists. The average time elapsed between the two consecutive FNAs was 18.3 +/- 11.2 (range, 4-48) months. Of the 45 patients, 23 presented with increase in size of the nodule and the remaining 22 patients did not have any change in size at the time of repeat FNA. Identical cytologic diagnoses were rendered in 39 of the 45 patients who underwent 2 or 3 consecutive FNA. Repeat FNA did not result in detection of any malignant neoplasms. Thyroid resection in 7 patients with increased nodule size and pressure symptoms confirmed the cytologic impressions of benign thyroid nodular disease. Our results show that the routine performance of repeated FNA cytology in the follow-up of patients with benign nodular thyroid disease with or without any clinical changes is of limited usefulness. Clinical factors rather than repeat FNA may hold precedence in surgical management of patients with benign nodular thyroid disease.

The clinical application and cost analysis of fine-needle aspiration biopsy in the diagnosis of mass lesions in sarcoidosis.

BACKGROUND: Sarcoidosis is a prevalent disease of unknown cause characterized by granulomatous inflammation that often creates deep and/or superficial mass lesions. Tissue samples are considered the "gold standard" in diagnosis; however, it is a medically treated disease. We analyzed the utility and relative cost-effectiveness of fine-needle aspiration biopsy (FNAB) in the clinical investigation of patients with both suspected and unsuspected sarcoidosis. METHODS: All FNAB cases with sarcoidosis either as the cytologic diagnosis or mentioned as part of the differential diagnosis were retrospectively reviewed for clinical history, follow-up, cytologic features, and surgical pathology findings. Comparative analysis of cost of FNAB and excisional biopsy were also made. RESULTS: Thirty-two FNABs in 28 patients included 17 women and 11 men. Anatomic sites included lymph node (n = 17), lung (n = 5), salivary gland (n = 8), and liver (n = 2). Sarcoidosis had already been diagnosed or was a clinical consideration prior to FNAB in 14 cases. Chest radiograph showed abnormal findings in 19 cases. Angiotensin-converting enzyme (ACE) was measured in seven patients and was elevated in four. All aspirates showed granulomatous inflammation; in 22 patients, special stains or cultures for microorganisms were negative. Simultaneous or subsequent excisional biopsies confirmed the FNAB findings in 17 patients. Institutional ratios of excisional biopsy to FNAB in the diagnosis of sarcoidosis ranged from 4 to 19:1. The cost of FNAB was only 12.5 to 50% that of tissue biopsy. CONCLUSIONS: FNAB appears to be underutilized in the diagnosis of sarcoidosis. When used in conjunction with radiologic and laboratory data, FNAB may be a reliable and cost-effective method of diagnosis, especially in patients with an established diagnosis of sarcoidosis.

Isolation and characterization of human breast adenocarcinoma cells made resistant to alpha-difluoromethylornithine.

Human breast adenocarcinoma cells MCF-7 were selected for resistance to ornithine decarboxylase (ODC) inhibitor, alpha-difluoromethylornithine (DFMO). Stepwise increments of the concentration of DFMO resulted in selection of MCF-7 cells that were capable of growing in the presence of 1.0 mM DFMO. This capacity was associated with a 10-fold increase in ODC activity and marked enhancement in the synthesis rate of ODC protein as verified by a 2-hr [35S]methionine labeling of cellular proteins followed by immunoprecipitation and SDS-PAGE. The resistant cells had much higher concentration of putrescine, spermidine, and spermine than the control cells. A 25-fold increase in ED50 (effective dose causing 50% inhibition) for the antiproliferative action of DFMO in these resistant cells was observed. The susceptibility of wild-type and resistant cell lines to other inhibitors of the polyamine biosynthetic pathway and adriamycin is also reported.

Prophylactic mastectomy: pathologic findings in high-risk patients.

BACKGROUND: According to recently published data, prophylactic mastectomy (PM) appears to prevent about 90% of the expected malignant neoplasms in women with a family history of breast cancer. OBJECTIVES: To identify the frequency of high-risk lesions in PM specimens and to determine occurrence of any new primary breast cancer following PM. DESIGN: We performed a retrospective study of women undergoing unilateral or bilateral PM. Medical charts and pathologic findings of 35 patients who underwent bilateral mastectomies at University Hospital, Syracuse, NY, from 1989 to 1996 were reviewed. Patients with biopsy-proven bilateral breast cancer were excluded. Patients were divided into 3 groups: (A) positive family history and no known breast cancer (n = 9), (B) positive family history and contralateral neoplasia (n = 13), and (C) negative family history and contralateral neoplasia (n = 13). These findings were compared with those found in reduction mammoplasty specimens from 10 women at standard risk of breast cancer. RESULTS: The mean age of the control group of women undergoing reduction mammoplasty was 38 years. The pathologic specimens demonstrated no significant pathologic findings in 9 and fibrocystic change in 1. In group A, the mean number of affected relatives was 3.1, and the mean age was 38 years. Two of these 9 women had atypical duct hyperplasia and 1 had atypical lobular hyperplasia in their breasts (ie, 33% with high-risk pathologic findings). Of the 13 group B women (mean age, 46.6 years; mean of 2.5 affected relatives and unilateral breast cancer), the contralateral PM specimen contained duct carcinoma in situ in one and invasive ductal cancer in a second (15% with occult malignant neoplasms). In 13 group C patients (mean age, 47.1 years), 3 (23.1%) of the contralateral PM specimens displayed atypical duct hyperplasia or atypical lobular hyperplasia. At a mean follow-up of 4.8 years, there have been no new breast malignant neoplasms in these 45 women. CONCLUSIONS: The occurrence of unilateral cancer in patients with family history of breast cancer is associated with a 15.4% probability of simultaneous occult malignant neoplasms in the contralateral breast. Patients with a strong family history but no evidence of breast cancer have a substantially similar rate of proliferative disease in their PM specimens as those women who have unilateral cancer but no significant family history.

Papillary thyroid carcinoma with nodular fasciitis-like stroma. Pitfalls in fine-needle aspiration cytology.

Papillary thyroid carcinoma with nodular fasciitis-like stroma is one of the rare variants of papillary thyroid carcinoma. The problems posed by the exuberant nodular fasciitis-like stroma, which obscures the neoplastic nature of the tumor, are recognized in surgical pathology but have received little attention in the cytopathology literature. We report a rare case of papillary thyroid carcinoma in which nodular fasciitis-like stroma posed difficulty on fine-needle aspiration cytology. The differential diagnosis of fibroproliferative processes in thyroid fine-needle aspirations is also discussed.

Diagnostic accuracy and clinical utility of endoscopic bile duct brushing in the evaluation of biliary strictures.

Pathologic evidence of malignancy in biliary strictures is useful in the preoperative setting because it helps define therapeutic planning and prognosis. The purpose of this study was to assess the diagnostic accuracy and clinical utility of endoscopic bile duct brushings in the evaluation of bile duct strictures. We retrospectively evaluated 34 endoscopic biliary brushings derived from 31 patients with bile duct strictures. Relevant clinical and follow-up data were collected. Histologic specimens were reviewed in patients undergoing subsequent biopsies. Patients included 18 men and 13 women with an age range of 25 to 79 years (mean, 52 years). All patients had histologic and/or clinical follow-up. Cytologic diagnosis included cholangiocarcinoma (14.7%), suspicious for cholangiocarcinoma (5.9%), atypical hyperplasia (17.6%), and negative for malignancy (61.7%). All positive diagnoses were confirmed by histologic testing (false-positive rate, 0%). The cases that were suspicious for cholangiocarcinoma and the 5 atypical hyperplasia cases were also subsequently diagnosed as cholangiocarcinoma by biopsy. One atypical case was diagnosed as pancreatic carcinoma. All 21 negative cases were confirmed by biopsies (15) and clinical follow-up (6) (false-negative rate, 20%). Endoscopic bile duct brushing is diagnostically accurate and hence clinically useful in the management of patients with bile duct strictures. Atypical hyperplasias may contribute to diagnostic pitfalls leading to false-positive and false-negative diagnoses.

Maintenance of increased Bcl-2 expression in uterine leiomyomas after GnRH agonist therapy.

OBJECTIVE: To compare the immunohistochemical expression of Bcl-2 in uterine leiomyomas in patients undergoing myomectomy or hysterectomy with and without preoperative treatment with the gonadotropin-releasing hormone receptor agonist (GnRH-a) leuprolide acetate (LA). STUDY DESIGN: Retrospective case-control study. Seventeen patients with symptomatic uterine leiomyomata were included. Of the 17 patients, 7 were treated with LA (3.75 mg) in three monthly doses prior to myomectomy or hysterectomy. Ten patients who did not receive LA and underwent hysterectomy for leiomyomas served as controls. Formalin-fixed, paraffin-embedded archival tissue from 17 leiomyomas were immunostained with a monoclonal antibody against Bcl-2 protein. Positivity was scored semiquantitatively on a three-tier scale. RESULTS: Immunostaining for Bcl-2 protein was intense (2-3+) in 7 LA-treated and 10 untreated leiomyomas but was scarce (0-1+) in normal myometrial smooth muscle. CONCLUSION: Abundant expression of Bcl-2 protein may be responsible for the growth of leiomyomas by preventing apoptotic cell death. Its increased expression is maintained in GnRH-a-treated leiomyomas.