Biopsias mamarias bajo resonancia magnética, experiencia preliminar / Breast biopsies performed under MRI, preliminary experience

La resonancia magnética (RM) mamaria se está convirtiendo en una herramienta de trabajo frecuentemente utilizada en nuestro medio. Existe un grupo de lesiones que sólo pueden ser identificadas por esta técnica, RMI only. Entre 14 a 20 por ciento de ellas serán malignas, según las diferentes series publicadas. Este tipo de lesiones requieren de biopsia guiada bajo RM. Pacientes y Métodos: se realizó revisión retrospectiva descriptiva de las biopsias asistidas por vacío realizadas en nuestra institución (período entre agosto de 2008 y junio de 2013). Resultados: El 0,3 por ciento (11) de las biopsias realizadas en nuestra institución fueron realizadas bajo RM, en 9 mujeres. En el 55 por ciento de los casos la indicación de la resonancia en la que se detectó la lesión biopsiada, fue etapificación de cáncer mamario recientemente diagnosticado; en el 100 porciento de los casos se realizó ultrasonido de segunda mirada, las lesiones tenían un tamaño promedio de 15 mm (4-29), un 63,6 por ciento fueron nódulos y el resto captaciones tipo no masa. La duración de la biopsia varió entre 40 y 130 minutos, un 27,2 por ciento resultaron lesiones malignas; 36,4 por ciento lesiones de alto riesgo; y 36,4 por ciento benignas. En el 45,5 por ciento el resultado de la biopsia bajo resonancia cambia la conducta quirúrgica. De las 7 lesiones operadas hubo subestimación en un caso de cáncer ductal in situ, que resultó cáncer ductal infiltrante. En el resto la histología quirúrgica fue idéntica a la de la biopsia bajo resonancia. Conclusión: Las biopsias bajo resonancia son infrecuentes, consumen un tiempo considerable, su correlación histológica es muy confiable y cambia la conducta quirúrgica casi en la mitad de los casos, lo cual tiene implicancias en el pronóstico de la paciente.

Abstract. Breast MRI is becoming a frequently used working tool in our environment. A group of lesions exist that can only be identified by this technique, "MRI only". Between 14-20 % of these will be malignant, according to various published series. Such lesions require biopsy guided under MRI. Patients and Methods: A descriptive retrospective review of vacuum-assisted biopsies was performed at our institution (period between August 2008 and June 2013). Results: 0.3 % (11) of the biopsies performed at our institution were done so under MRI, in 9 women. In 55% of the cases the resonance indication in which the biopsied lesion was detected, was newly diagnosed staging of breast cancer; in 100% of the cases a second-look ultrasound was performed, the lesions had an average size of 15 mm (4-29), 63.6% were nodules and the remainder other non-mass type deposits. The duration of the biopsy varied between 40 and 130 min, 27.2% were malignant lesions, 36.4 % high-risk lesions, and 36.4 % benign. In 45.5% the result of the biopsy performed under MRI changed the surgical procedure. Of the 7 operated lesions there was an underestimation in one case of ductal carcinoma in situ, which resulted being invasive ductal carcinoma. In the remainder, the surgical histology was identical to that of the biopsy performed under magnetic resonance. Conclusion: Biopsies performed under MRI are infrequent, they take considerable time, their histological correlation is very reliable and it changes the surgical procedure in almost half of the cases, which has implications in the prognosis of the patient.

Caracterización de lesiones asociadas a microcalcificaciones BI-RADS 4A, en 11 años de biopsias estereotáxicas / Characterization of lesions associated with microcalcifications BI-RADS 4A over a 11-year period of stereotactic breast biopsies

Substantial advances in breast imaging techniques, especially developments in digital mammography, have led to early detection of breast cancer. It is well-known that microcalcifications are present in approximately 55 percent of nonpalpable breast malignancies and are responsible for the detection of 85-90 percent of cases of ductal carcinoma in situ (DCIS) through mammographic screening. We evaluated the types of associated lesions and the percentage of malignancy in BI-RADS 4A subcategory (low suspicion of malignancy), by performing a database review of stereotactic biopsies of microcalcifications categorized as BI-RADS 4A, between September 1999 and January 2011, which accounted for 21.4 percent of biopsied microcalcifications in a total of 159 women. Histological findings corresponded to benign lesions in 43.5 percent, high-risk lesions in 46.5 percent, and malignant tumors in 10 percent. Concerning the latter (16 biopsies), 81.3 percent were DCIS and 18.7 percent corresponded to infiltrating ductal carcinoma (IDC). The PPV of BI-RADS 4 A category was 13 percent, a value consistent with that described in the literature. Microcalcifications BI-RADS 4A exhibit low suspicion of malignancy, since they mostly correspond to benign lesions (90 percent). Subcategory 4A constitutes an important ancillary diagnostic tool for a more accurate assessment of lesions suspicious for malignancy; therefore, we strongly recommend its use.

El continuo avance en las técnicas de imágenes mamarias, especialmente el desarrollo de la mamografía digital, ha permitido detectar cáncer mamario en etapa precoz. Se sabe que las microcalcificaciones están presentes en el 55 por ciento de los cánceres no palpables y corresponden al 85-90 por ciento de los carcinomas ductales in situ (CDIS) que se detectan con mamografía de screening. Hemos evaluado el tipo de lesiones asociadas y el porcentaje de malignidad de la subcategoría BI-RADS 4A (baja sospecha de malignidad), realizando una revisión de la base de datos de las biopsias estereotáxicas por microcalcificaciones categorizadas BI-RADS 4A entre septiembre 1999 y enero 2011 y que alcanzaron al 21,4 por ciento del total de las microcalcificaciones biopsiadas, en un total de 159 mujeres. Los resultados histológicos correspondieron a lesiones benignas en el 43,5 por ciento, lesiones de alto riesgo en el 46,5 por ciento y malignas en 10 por ciento. De las lesiones malignas (16 biopsias), el 81,3 por ciento fue CDIS y el 18,7 por ciento carcinoma ductal infiltrante (CDI). El VPP de la categoría BI-RADS 4 A fue de 13 por ciento, concordante con la literatura. Las microcalcificaciones BI-RADS 4A son de baja sospecha de malignidad, correspondiendo en su gran mayoría (90 por ciento) a lesiones benignas. La subdivisión en 4 A representa una herramienta que facilita un mejor manejo clínico de las pacientes, por lo que recomendamos su utilización.

Resonancia magnética mamaria preoperatoria: la gran polémica / Preoperative breast MRI: the great controversy

Preoperative examination intended to detect multifocality, multicentricity and bilaterality-once considered the strongest indication of breast magnetic resonance imaging (MRI)-is currently being strongly questioned in medical literature. This paper aims at evaluating, based on our experience at Clínica Alemana, Santiago, Chile, breast MRI ability to improve preoperative radiological tumour staging by conventional methods, as well as to determine the proportion of patients in which this diagnostic procedure generated changes in the surgical management. We retrospectively reviewed preoperative MRI studies carried out between January 2009 and June 2010. Classification: Group 1: MRI provided no new information. Group 2: by detecting additional lesions, MRI improved radiological staging without changing the type of surgery planned. Group 3: MRI showed new benign lesions and caused unnecessary surgery. Group 4: MRI successfully changed the type of surgery planned based on conventional studies. A total of 419 breast MRI scans were performed during a 18-month period; 39 percent of them were carried out preoperatively. For the analysis, 128 patients were enrolled and distributed in the following categories: Group 1 (66 percent), Group 2 (20 percent), Group 3 (2 percent) and Group 4 (12 percent). In 95.3 percent of the patients, a single surgery with clear margins was performed. This work demonstrated the usefulness of preoperative MRI in our practice, i.e., it allowed for a better radiological staging in one third of the patients and even successfully changed the surgical approach in 12 percent of cases.

El estudio preoperatorio en búsqueda de multifocalidad, multicentricidad y bilateralidad -antes considerada la indicación más sólida de la resonancia magnética (RM) mamaria- hoy se encuentra fuertemente cuestionada en la literatura. En este trabajo nos propusimos evaluar la capacidad de la RM mamaria en nuestro centro para mejorar la etapificación radiológica preoperatoria realizada por métodos convencionales y determinar la proporción de las pacientes en que genera cambio en el enfoque quirúrgico. Hemos revisado retrospectivamente las RM preoperatorias entre enero de 2009 y junio de 2010. Clasificación: Grupo1: la RM no aportó información nueva. Grupo 2: al detectar lesiones adicionales, mejoró la etapificación radiológica, sin cambiar el tipo de la cirugía planificada. Grupo3: demostró nuevas lesiones no malignas y causó cirugía inútil. Grupo 4: cambió correctamente el tipo de cirugía planeada en base a los estudios convencionales. En los 18 meses se realizaron 419 RM mamarias, el 39 por ciento de ellas en preoperatorio. Para el análisis se han reclutado 128 pacientes con la siguiente distribución en los grupos predeterminados: Grupo 1(66 por ciento), Grupo 2(20 por ciento), Grupo 3(2 por ciento) y Grupo 4(12 por ciento). En el 95,3 por ciento de las pacientes se logró realizar una sola cirugía con márgenes libres. Este trabajo demostró la utilidad de la RM preoperatoria en nuestra práctica: permite una mejor etapificación radiológica en el tercio de las pacientes e incluso cambia correctamente el enfoque quirúrgico en el 12 por ciento de los casos.

Quistes retro-aeeolares en adolescentes: aspectos clínicos y ultrasonograficos / Retro-areolar cysts in adolescents: clinical and ultrasonographic aspects

Retroareolar cysts are common in pre and postmenarchic girls. Boys are rarely diagnosed with this condition. They correspond to cystic dilatations of the accessory mammary glands that open along with a sebaceous gland at the areola and can be single or multiple, uni or bilateral, palpable or incidental findings on ultrasound. They have variable morphology, thin walls, anechogenic content, sometimes calcic sediment can be observed in their lumen. Infected cysts present enlarged, hypervascularized walls; their content is echogenic, avascular and the adjacent tissue is hyperechogenic, with increased vascularization at color Doppler. If not treated, may become retroareolar abscesses. Inflamatory complications are treated with anti-inflamatory drugs and/or antibiotics. No diagnostic biopsy or puncture aspiration is required, since they are spontaneously drained at the areola. In order to appropriately advise patients and families, it is necessary to have knowledge of both the medical and the ultrasonographic aspects of them and their complications.

Los quistes retroareolares son frecuentes en niñas pre y postmenárquicas. Raramente se diagnostican en el varón. Corresponden a dilataciones quísticas de glándulas mamarias accesorias que se abren junto con una glándula sebácea en la areola, pueden ser únicos o múltiples, uni o bilaterales, palpables o hallazgos incidentales en ecografía. Los no complicados tienen morfología variable, paredes delgadas y contenido anecogénico, pudiendo observarse sedimento calcico en su lumen. Los complicados presentan paredes engrosadas, hipervascularizadas, con contenido ecogénico, avascular, tejidos adyacentes hiperecogénicos y aumento de la vascularización al Doppler color. Sin tratamiento, pueden transformarse en abscesos retroareolares. La complicación inflamatoria se trata con antiinflamatorios y/o antibióticos. No requieren biopsia diagnóstica ni punción evacuadora, puesto que se drenan espontáneamente a la areola. El conocimiento del cuadro clínico y su aspecto ul-trasonográfico permitirá orientar adecuadamente a los pacientes y sus familias.

The activation mechanism of class-C G-protein coupled receptors.

Class-C G-protein coupled receptors (GPCRs) represent a distant group among the large family of GPCRs. This class includes the receptors for the main neurotransmitters, glutamate and gamma-aminobutyric acid (GABA), and the receptors for Ca(2+), some taste and pheromone molecules, as well as some orphan receptors. Like any other GPCRs, class-C receptors possess a heptahelical domain (HD) involved in heterotrimeric G-protein activation, but most of them also have a large extracellular domain (ECD) responsible for agonist recognition and binding. In addition, it is now well accepted that these receptors are dimers, either homo or heterodimers. This complex architecture raises a number of important questions. Here we will discuss our view of how agonist binding within the large ECD triggers the necessary change of conformation, or stabilize a specific conformation, of the heptahelical domain leading to G-protein activation. How ligands acting within the heptahelical domain can change the properties of these complex macromolecules.

Allosteric interactions between GB1 and GB2 subunits are required for optimal GABA(B) receptor function.

Recent studies on G-protein-coupled receptors revealed that they can dimerize. However, the role of each subunit in the activation process remains unclear. The gamma-amino-n-butyric acid type B (GABA(B)) receptor is comprised of two subunits: GB1 and GB2. Both consist of an extracellular domain (ECD) and a heptahelical domain composed of seven transmembrane alpha-helices, loops and the C-terminus (HD). Whereas GB1 ECD plays a critical role in ligand binding, GB2 is required not only to target GB1 subunit to the cell surface but also for receptor activation. Here, by analysing chimeric GB subunits, we show that only GB2 HD contains the determinants required for G-protein signalling. However, the HD of GB1 improves coupling efficacy. Conversely, although GB1 ECD is sufficient to bind GABA(B) ligands, the ECD of GB2 increases the agonist affinity on GB1, and is necessary for agonist activation of the receptor. These data indicate that multiple allosteric interactions between the two subunits are required for wild-type functioning of the GABA(B) receptor and highlight further the importance of the dimerization process in GPCR activation.

Mapping the agonist-binding site of GABAB type 1 subunit sheds light on the activation process of GABAB receptors.

The gamma-amino-n-butyric acid type B (GABA(B)) receptor is composed of two subunits, GABA(B)1 and GABA(B)2, belonging to the family 3 heptahelix receptors. These proteins possess two domains, a seven transmembrane core and an extracellular domain containing the agonist binding site. This binding domain is likely to fold like bacterial periplasmic binding proteins that are constituted of two lobes that close upon ligand binding. Here, using molecular modeling and site-directed mutagenesis, we have identified residues in the GABA(B)1 subunit that are critical for agonist binding and activation of the heteromeric receptor. Our data suggest that two residues (Ser(246) and Asp(471)) located within lobe I form H bonds and a salt bridge with carboxylic and amino groups of GABA, respectively, demonstrating the pivotal role of lobe I in agonist binding. Interestingly, our data also suggest that a residue within lobe II (Tyr(366)) interacts with the agonists in a closed form model of the binding domain, and its mutation into Ala converts the agonist baclofen into an antagonist. These data demonstrate the pivotal role played by the GABA(B)1 subunit in the activation of the heteromeric GABA(B) receptor and are consistent with the idea that a closed state of the binding domain of family 3 receptors is required for their activation.

Conservation of the ligand recognition site of metabotropic glutamate receptors during evolution.

Mammalian metabotropic glutamate receptors (mGluRs) are classified into 3 groups based on their sequence similarity and ligand recognition selectivity. Recently, we identified a Drosophila mGluR (DmGlu(A)R) which is about equidistant, phylogenetically, from the 3 mGluR groups. However, both the G-protein coupling selectivity and the pharmacological profile of DmGlu(A)R, as analysed with mutated G-proteins and a few compounds, look similar to those of mammalian group-II mGluRs. In the present study we carefully examined the pharmacological profile of DmGlu(A)R, and compared it to those of the rat mGlu(1a), mGlu(2) and mGlu(4a) receptors, representative of group-I, II and III respectively. The pharmacological profile of DmGlu(A)R was found to be similar to that of mGlu(2)R, and only very small differences could be identified at the level of their pharmacophore models. These data strongly suggest that the binding sites of these two receptors are similar. To further document this idea, a 3D model of the mGlu(2) binding domain was constructed based on the low sequence similarity with periplasmic amino acid binding proteins, and was used to identify the residues that possibly constitute the ligand recognition pocket. Interestingly, this putative binding pocket was found to be very well conserved between DmGlu(A)R and the mammalian group-II receptors. These data indicate that there has been a strong selective pressure during evolution to maintain the ligand recognition selectivity of mGluRs.

Ca(2+) requirement for high-affinity gamma-aminobutyric acid (GABA) binding at GABA(B) receptors: involvement of serine 269 of the GABA(B)R1 subunit.

The gamma-aminobutyric acid (GABA) receptor type B (GABA(B)R) is constituted of at least two homologous proteins, GABA(B)R1 and GABA(B)R2. These proteins share sequence and structural similarity with metabotropic glutamate and Ca(2+)-sensing receptors, both of which are sensitive to Ca(2+). Using rat brain membranes, we report here that the affinity of GABA and 3-aminopropylphosphinic acid for the GABA(B)R receptor is decreased by a factor >10 in the absence of Ca(2+). Such a large effect of Ca(2+) is not observed with baclofen or the antagonists CGP64213 and CGP56999A. In contrast to baclofen, the potency of GABA in stimulating GTPgammaS binding in rat brain membranes is also decreased by a factor >10 upon Ca(2+) removal. The potency for Ca(2+) in regulating GABA affinity was 37 microM. In cells expressing GABA(B)R1, the potency of GABA, but not of baclofen, in displacing bound (125)I-CGP64213 was similarly decreased in the absence of Ca(2+). To identify residues that are responsible for the Ca(2+) effect, the pharmacological profile and the Ca(2+) sensitivity of a series of GABA(B)R1 mutants were examined. The mutation of Ser269 into Ala was found to decrease the affinity of GABA, but not of baclofen, and the GABA affinity was found not to be affected upon Ca(2+) removal. Finally, the effect of Ca(2+) on the GABA(B) receptor function is no longer observed in cells coexpressing this GABA(B)R1-S269A mutant and the wild-type GABA(B)R2. Taken together, these results show that Ser269, which is conserved in the GABA(B)R1 protein from Caenorhabditis elegans to mammals, is critical for the Ca(2+)-effect on the heteromeric GABA(B) receptor.

Three-dimensional model of the extracellular domain of the type 4a metabotropic glutamate receptor: new insights into the activation process.

Metabotropic glutamate receptors (mGluRs) belong to the family 3 of G-protein-coupled receptors. On these proteins, agonist binding on the extracellular domain leads to conformational changes in the 7-transmembrane domains required for G-protein activation. To elucidate the structural features that might be responsible for such an activation mechanism, we have generated models of the amino terminal domain (ATD) of type 4 mGluR (mGlu4R). The fold recognition search allowed the identification of three hits with a low sequence identity, but with high secondary structure conservation: leucine isoleucine valine-binding protein (LIVBP) and leucine-binding protein (LBP) as already known, and acetamide-binding protein (AmiC). These proteins are characterized by a bilobate structure in an open state for LIVBP/LBP and a closed state for AmiC, with ligand binding in the cleft. Models for both open and closed forms of mGlu4R ATD have been generated. ACPT-I (1-aminocyclopentane 1,3,4-tricarboxylic acid), a selective agonist, has been docked in the two models. In the open form, ACPT-I is only bound to lobe I through interactions with Lys74, Arg78, Ser159, and Thr182. In the closed form, ACPT-I is trapped between both lobes with additional binding to Tyr230, Asp312, Ser313, and Lys317 from lobe II. These results support the hypothesis that mGluR agonists bind a closed form of the ATDs, suggesting that such a conformation of the binding domain corresponds to the active conformation.

Mutagenesis and modeling of the GABAB receptor extracellular domain support a venus flytrap mechanism for ligand binding.

The gamma-aminobutyric acid type B (GABAB) receptor is distantly related to the metabotropic glutamate receptor-like family of G-protein-coupled receptors (family 3). Sequence comparison revealed that, like metabotropic glutamate receptors, the extracellular domain of the two GABAB receptor splice variants possesses an identical region homologous to the bacterial periplasmic leucine-binding protein (LBP), but lacks the cysteine-rich region common to all other family 3 receptors. A three-dimensional model of the LBP-like domain of the GABAB receptor was constructed based on the known structure of LBP. This model predicts that four of the five cysteine residues found in this GABAB receptor domain are important for its correct folding. This conclusion is supported by analysis of mutations of these Cys residues and a decrease in the thermostability of the binding site after dithiothreitol treatment. Additionally, Ser-246 was found to be critical for CGP64213 binding. Interestingly, this residue aligns with Ser-79 of LBP, which forms a hydrogen bond with the ligand. The mutation of Ser-269 was found to differently affect the affinity of various ligands, indicating that this residue is involved in the selectivity of recognition of GABAB receptor ligands. Finally, the mutation of two residues, Ser-247 and Gln-312, was found to increase the affinity for agonists and to decrease the affinity for antagonists. Such an effect of point mutations can be explained by the Venus flytrap model for receptor activation. This model proposes that the initial step in the activation of the receptor by agonist results from the closure of the two lobes of the binding domain.

Paranodin, a glycoprotein of neuronal paranodal membranes.

Ranvier nodes are flanked by paranodal regions, at the level of which oligodendrocytes or Schwann cells interact closely with axons. Paranodes play a critical role in the physiological properties of myelinated nerve fibers. Paranodin, a prominent 180 kDa transmembrane neuronal glycoprotein, was purified and cloned from adult rat brain, and found to be highly concentrated in axonal membranes at their junction with myelinating glial cells, in paranodes of central and peripheral nerve fibers. The large extracellular domain of paranodin is related to neurexins, and its short intracellular tail binds protein 4.1, a cytoskeleton-anchoring protein. Paranodin may be a critical component of the macromolecular complex involved in the tight interactions between axons and myelinating glial cells characteristic of the paranodal region.

Changes in the carboxyl-terminal domain of metabotropic glutamate receptor 1 by alternative splicing generate receptors with differing agonist-independent activity.

The metabotropic glutamate receptors (mGluRs) share no sequence homology and show different structural features compared with most other G protein-coupled receptors (GPCRs). In particular, some isoforms of the phospholipase C (PLC)-coupled mGluRs (mGluR1a, mGluR5a, and mGluR5b) have a surprisingly long carboxyl-terminal intracellular domain of more than 350 residues, whereas the splice variants mGluR1b and mGluR1c have a much shorter carboxyl terminus. In the current study, the different splice variants of mGluR1 were expressed in porcine kidney epithelial (LLC-PK1) or the human embryonic kidney (HEK 293) cells, and their levels of expression were examined with the use of Western blot analysis. Expression of the short isoforms mGluR1b and mGluR1c did not modify the basal inositol phosphate production. In contrast, expression to similar levels of mGluR1a resulted in a 2-fold increase in the basal inositol phosphate formation. This increase in basal PLC activity was due to neither the presence of a low concentration of glutamate in the incubation medium nor a modification of the PLC pathway, resulting, for example, from the constant activation of mGluR1a++ by glutamate during the culture. Surprisingly none of the known competitive antagonists of mGluR1 inhibited the basal PLC activity, indicating that none of these molecules act as inverse agonists. Taken together, these results indicate that the long carboxyl-terminal domain confers a small agonist-independent activity to mGluR1. This indicates that, as already observed for other GPCRs, little constitutive activity of wild-type mGluRs can be detected. Our results also add to the splice variants and further suggest that the long carboxyl-terminal domain of mGluR1a confers better coupling efficiency to the G proteins.

Impact of an educational program for the prevention of colonization of intravascular catheters.

OBJECTIVE: To evaluate the efficacy of an educational program for the prevention of catheter colonization. DESIGN: Two cross-sectional studies were carried out in a 500-bed randomly selected area of the hospital, separated by an educational program on the care of intravenous lines based on the Centers for Disease Control and Prevention (CDC) recommendations for the control of catheter-related infections. SETTING: A 2,100-bed urban general hospital affiliated with the University of Madrid (Spain). METHODS: Characteristics of patients and catheters and appropriateness of catheter care were evaluated. Cultures were taken from the point of insertion of the vascular catheter, the hubs, and infusion fluids. When catheter-associated infection was suspected, the distal end of the catheter was sent for culture and two blood cultures were taken. We compared the clinical and microbiological data before and after carrying out an educational program based on CDC recommendations for the control of catheter-related infections. RESULTS: Characteristics of patients and catheters did not differ between the two cross-sectional studies. Compared with baseline data, after the educational program we observed a reduction of inappropriate catheter care, from 83% to 38% (45% difference, 95% confidence interval [CI95], 55% to 35%, P < 0.0000), and a reduction in the rate of skin colonization, from 34% to 18% (16% difference, CI95, 26% to 5%, P < 0.001). The frequency of phlebitis (15% versus 14%), hub colonizations (12% versus 11%), catheter colonizations (2% versus 1%), and catheter-related bacteremias (0% versus 0%) remained unchanged between the two cross-sectional studies. CONCLUSIONS: Our educational program improved catheter care and reduced significantly the proportion of skin colonization around the insertion point. However, the educational program did not modify the proportion of hub colonization; because hub colonization has been demonstrated to be a source of line sepsis, our data suggest the need for a specific program directed to the maintenance of catheter hubs.