Inflammatory lesions and brain tumors: is it possible to differentiate them based on texture features in magnetic resonance imaging?

Neuroimaging strategies are essential to locate, to elucidate the etiology, and to the follow up of brain disease patients. Magnetic resonance imaging (MRI) provides good cerebral soft-tissue contrast detection and diagnostic sensitivity. Inflammatory lesions and tumors are common brain diseases that may present a similar pattern of a cerebral ring enhancing lesion on MRI, and non-enhancing core (which may reflect cystic components or necrosis) leading to misdiagnosis. Texture analysis (TA) and machine learning approaches are computer-aided diagnostic tools that can be used to assist radiologists in such decisions. Methods: In this study, we combined texture features with machine learning (ML) methods aiming to differentiate brain tumors from inflammatory lesions in magnetic resonance imaging. Retrospective examination of 67 patients, with a pattern of a cerebral ring enhancing lesion, 30 with inflammatory, and 37 with tumoral lesions were selected. Three different MRI sequences and textural features were extracted using gray level co-occurrence matrix and gray level run length. All diagnoses were confirmed by histopathology, laboratorial analysis or MRI. Results: The features extracted were processed for the application of ML methods that performed the classification. T1-weighted images proved to be the best sequence for classification, in which the differentiation between inflammatory and tumoral lesions presented high accuracy (0.827), area under ROC curve (0.906), precision (0.837), and recall (0.912). Conclusion: The algorithm obtained textures capable of differentiating brain tumors from inflammatory lesions, on T1-weghted images without contrast medium using the Random Forest machine learning classifier.(AU)

Semi-quantitative evaluation of brain gliomas in adults: A focus on neuropathological characteristics

Introduction: Gliomas are neoplasms with high recurrence and mortality. Due to the difficulty to apply the World Health Organization (2016) classification, developing countries continue to use histological evaluation to diagnose and classify these neoplasms. Objective: To develop a semi-quantitative scale to numerically grade gliomas by its morphological characteristics. Method: A cohort of patients with gliomas was assessed and followed for 36 months. Tumor tissue sections were analyzed and graded, including aspects such as cell line, cellularity, nuclear pleomorphism, mitosis, endothelial hyperplasia, hypoxic changes, apoptotic bodies, necrosis, hemorrhage and proliferation index. Results: 58 cases were analyzed. Low-grade gliomas median score was 12 points (9 and 13.5 for percentiles 25 and 75, respectively), whereas for high-grade gliomas it was 17 points (16 and 20.5 for percentiles 25 and 75, respectively) (p < 0.0001). Thirty-six-month survival of patients with low (13/17) and high grade gliomas (6/41) was also significantly different (p < 0.0001). Conclusions: The semi-quantitative morphological scale allows an objective evaluation of gliomas, with an adequate correlation between the score, tumor grade and survival time.

Aspectos epidemiológicos, clínicos y quirúrgicos de los tumores cerebrales metastásicos / Aspectos epidemiológicos, clínicos e cirúrgicos dos tumores cerebrais metastáticos / Epidemiological, clinical and surgical aspects of metastatic brain tumors

Introducción: los tumores que se diseminan en el cerebro, provenientes de una neoplasia primaria localizada en otros órganos del cuerpo son conocidos como tumores cerebrales metastásicos. Se estima que el 25 por ciento de los tumores malignos en otros lugares del organismo provocan metástasis en la cabeza. Objetivo: sistematizar los aspectos clínicos, epidemiológicos y quirúrgicos de los tumores cerebrales metastásicos, así como las herramientas diagnósticas y terapéuticas necesarias para ofrecerles al enfermo y familiares las mejores alternativas ante la enfermedad. Método: se realizó una revisión narrativa a partir del estudio documental de revisiones sistemáticas, metaanálisis, guías de práctica clínica, artículos originales y tesis doctorales que se encontraron en las bases de datos electrónicas. Resultados: la incidencia de la metástasis cerebral varía en dependencia de la localización del tumor primario. En los adultos, la incidencia más alta se observó entre la quinta y séptima década de vida, sin diferencias en el sexo. Los tumores cerebrales tienen diferentes formas de presentación clínica, entre ellas se encontraron el síndrome de hipertensión intracraneal, signos focales, crisis epilépticas y síndrome endocrino. Los tres componentes primordiales del manejo de pacientes con metástasis cerebral fueron las drogas no quimioterapéuticas y quimioterapéuticas, la intervención quirúrgica para la exéresis tumoral y la radioterapia. Conclusiones: los tumores metastásicos cerebrales constituyen un problema de salud con incidencia creciente, con un cuadro sindrómico complejo y polimorfo, poseen amplio arsenal terapéutico que abarca las drogas no quimioterapéuticas, la quimioterapia, la quirúrgica y la radioterapia las cuales deben ser ajustadas a las características de cada paciente para lograr una sobrevida lo más larga posible, con mayor calidad de vida(AU)

Introduction: tumors that spread in the brain, from a primary neoplasm located in other organs of the body are known as metastatic brain tumors. It is estimated that 25per cent of malignant tumors in other parts of the body cause head metastases. Objective: to systematize the clinical, epidemiological and surgical aspects of metastatic brain tumors, as well as the diagnostic and therapeutic tools necessary to offer the patient and family the best alternatives to the disease. Method: a narrative review was carried out based on the documentary study of systematic reviews, meta-analysis, clinical practice guides, original articles and doctoral theses that were found in the electronic databases. Results: the incidence of brain metastasis varies depending on the location of the primary tumor. In adults, the highest incidence was observed between the fifth and seventh decade of life, without differences in sex. Brain tumors have different forms of clinical presentation, including intracranial hypertension syndrome, focal signs, epileptic seizures and endocrine syndrome. The three primary ISSN 1028-9933 526 components of the management of patients with cerebral metastases were non-chemotherapeutic and chemotherapeutic drugs, surgical intervention for tumor excision and radiotherapy. Conclusions: metastatic brain tumors constitute a health problem with increasing incidence, with a complex syndromic and polymorphic picture, they have a wide therapeutic arsenal that includes non-chemotherapeutic drugs, chemotherapy, surgery and radiotherapy which must be adjusted to the characteristics of each patient to achieve a survival as long as possible, with a better quality of life(AU)

Introdução: tumores que se espalham no cérebro, a partir de uma neoplasia primária localizada em outros órgãos do corpo, são conhecidos como tumores cerebrais metastáticos. Estima-se que 25per cent dos tumores malignos em outras partes do corpo causem metástases na cabeça. Objetivo: sistematizar os aspectos clínicos, epidemiológicos e cirúrgicos dos tumores cerebrais metastáticos, bem como as ferramentas diagnósticas e terapêuticas necessárias para oferecer ao paciente e à família as melhores alternativas para a doença. Método: foi realizada uma revisão narrativa baseada no estudo documental de revisões sistemáticas, metanálises, guias de prática clínica, artigos originais e teses de doutorado encontradas nas bases de dados eletrônicas. Resultados: a incidência de metástases cerebrais varia de acordo com a localização do tumor primário. Nos adultos, a maior incidência foi observada entre a quinta e a sétima década de vida, sem diferenças entre os sexos. Os tumores cerebrais têm diferentes formas de apresentação clínica, incluindo síndrome de hipertensão intracraniana, sinais focais, convulsões epilépticas e síndrome endócrina. Os três componentes principais do tratamento de pacientes com metástases cerebrais foram medicamentos não quimioterápicos e quimioterápicos, intervenção cirúrgica para excisão de tumores e radioterapia. Conclusões: os tumores cerebrais metastáticos constituem um problema de saúde com incidência crescente, com quadro sindrômico e polimórfico complexo, possuem amplo arsenal terapêutico que abrange medicamentos não quimioterápicos, quimioterapia, cirurgia e radioterapia, que devem ser ajustados às características de cada paciente para alcançar a sobrevivência o maior tempo possível, com uma melhor qualidade de vida(AU)

An Improved Classification System for Brain Tumours Using Wavelet Transform and Neural Network / Un sistema de clasificación mejorado para los tumores cerebrales usando la transformada de ondeletas y la red neuronal

ABSTRACT This paper presents an improved classification system for brain tumours using wavelet transform and neural network. The anisotropic diffusion filter was used for image denoising, and the performance of the oriented rician noise reducing anisotropic diffusion (ORNRAD) filter was validated. The segmentation of the denoised image was carried out by fuzzy c-means clustering. The features were extracted using symlet and coiflet wavelet transforms, and the Levenberg-Marquardt algorithm based neural network was used to classify the magnetic resonance (MR) images. This classification technique of MR images was tested and analysed with existing methods, and its performance was found to be satisfactory with a classification accuracy of 93.24%. The developed system could assist physicians in classifying MR images for better decision-making.

RESUMEN Este artículo presenta un sistema de clasificación mejorado para los tumores de cerebro usando la transformada de ondeletas (transformada wavelet) y la red neuronal. El filtro de difusión anisotrópica fue utilizado para la eliminación del ruido de la imagen, y se validó el funcionamiento del filtro de difusión anisotrópica orientado a reducir el ruido riciano (ORNRAD, siglas en inglés). La segmentación de la imagen 'desruidizada ' (denoised) fue realizada mediante el agrupamiento difuso c-means fuzzy. Las características fueron extraídas usando las transformadas de ondeletas symlet y coiflet, y la red neuronal basada en el algoritmo de Levenberg-Marquardt fue utilizada para clasificar las imágenes de resonancia magnética (RM) imágenes. Esta técnica de clasificación de imágenes de RM fue probada y analizada con métodos existentes, y se halló que su rendimiento era satisfactorio con una precisión de clasificación de 93.24%. El sistema desarrollado podría ayudar a los médicos a clasificar imágenes de RM para una mejor toma de decisiones.

Estudio Descriptivo: Tratamiento Quirúrgico de los Meningiomas. Hospital "Santa Inés" Cuenca ­ Ecuador, 2011-2017 / Descriptive Research: Surgical Treatment of Meningiomas Hospital "Santa Inés" Cuenca - Ecuador, 2011-2017

INTRODUCCIÓN: En la actualidad se considera al tratamiento quirúrgico como la primera línea de intervención en meningiomas, el objetivo de esta investigación es describir los resultados y las estrategias actuales en el tratamiento quirúrgico de los meningiomas, que se realizan en el Hospital Santa Inés de Cuenca-Ecuador. METODO: Es un estudio descriptivo sobre el tratamiento quirúrgico de los meningiomas, haciendo énfasis en el tipo de abordaje empleado en el Hospital Santa Inés. Se describen las diferentes localizaciones anatómicas y situaciones fisiológicas específicas de pacientes con meningiomas. RESULTADOS: Se incluyeron 31 pacientes, 11 hombres y 20 mujeres. La edad al momento de la cirugía fue de 13 a 76 años. La localización más frecuente fue la convexidad y parasagital. El 6.45 % de los tumores se reportaron como atípicos. Se logró exéresis Simpson I y II en el 80.6 % de los pacientes. Hubo tres recurrencias, dos de ellas asociadas a la histopatología. No hubo mortalidad operatoria. CONCLUSIONES: La cirugía sigue siendo la primera opción de tratamiento, con resultados mejorados con las técnicas microquirúrgicas actuales y constituye un reto, primero por lograr la exéresis completa del tumor y luego por preservar la función neurológica (au)

BACKGROUD: At present the surgical treatment is considered as the first line in meningiomas, the aim of this study is to describe the outcomes and actual strategies in the surgical treatment of meningiomas treated at the Santa Ines Hospital in Cuenca-Ecuador. METHOD: It is a descriptive study on the surgical treatment of meningiomas, emphasizing the type of approach used in the Hospital Santa Inés. The different anatomical locations and specific physiological situations of patients with meningiomas are described. RESULTS: We included 31 patients, 11 men and 20 women. The age at the time of surgery was the between 13 to 76 years. The most frequent location was convexity and parasagittal. 6.45 % of the tumors were reported as atypical. Simpson I and II excision was achieved in 80.6 % of the patients. There were three recurrences, two associated with histopathology. There was no operative mortality. CONCLUSIONS: The surgery still is the first option of treatment, with better outcome due at the actual microsurgery techniques. The surgery is a challenge, at first achieve complete excision of the tumor and then to preserve the neurological function.(au)

Manual and semi-automatic quantification of in vivo ¹H-MRS data for the classification of human primary brain tumors

In vivo proton magnetic resonance spectroscopy (¹H-MRS) is a technique capable of assessing biochemical content and pathways in normal and pathological tissue. In the brain, ¹H-MRS complements the information given by magnetic resonance images. The main goal of the present study was to assess the accuracy of ¹H-MRS for the classification of brain tumors in a pilot study comparing results obtained by manual and semi-automatic quantification of metabolites. In vivo single-voxel ¹H-MRS was performed in 24 control subjects and 26 patients with brain neoplasms that included meningiomas, high-grade neuroglial tumors and pilocytic astrocytomas. Seven metabolite groups (lactate, lipids, N-acetyl-aspartate, glutamate and glutamine group, total creatine, total choline, myo-inositol) were evaluated in all spectra by two methods: a manual one consisting of integration of manually defined peak areas, and the advanced method for accurate, robust and efficient spectral fitting (AMARES), a semi-automatic quantification method implemented in the jMRUI software. Statistical methods included discriminant analysis and the leave-one-out cross-validation method. Both manual and semi-automatic analyses detected differences in metabolite content between tumor groups and controls (P < 0.005). The classification accuracy obtained with the manual method was 75 percent for high-grade neuroglial tumors, 55 percent for meningiomas and 56 percent for pilocytic astrocytomas, while for the semi-automatic method it was 78, 70, and 98 percent, respectively. Both methods classified all control subjects correctly. The study demonstrated that ¹H-MRS accurately differentiated normal from tumoral brain tissue and confirmed the superiority of the semi-automatic quantification method.

Classification of brain tumor extracts by high resolution ¹H MRS using partial least squares discriminant analysis

High resolution proton nuclear magnetic resonance spectroscopy (¹H MRS) can be used to detect biochemical changes in vitro caused by distinct pathologies. It can reveal distinct metabolic profiles of brain tumors although the accurate analysis and classification of different spectra remains a challenge. In this study, the pattern recognition method partial least squares discriminant analysis (PLS-DA) was used to classify 11.7 T ¹H MRS spectra of brain tissue extracts from patients with brain tumors into four classes (high-grade neuroglial, low-grade neuroglial, non-neuroglial, and metastasis) and a group of control brain tissue. PLS-DA revealed 9 metabolites as the most important in group differentiation: γ-aminobutyric acid, acetoacetate, alanine, creatine, glutamate/glutamine, glycine, myo-inositol, N-acetylaspartate, and choline compounds. Leave-one-out cross-validation showed that PLS-DA was efficient in group characterization. The metabolic patterns detected can be explained on the basis of previous multimodal studies of tumor metabolism and are consistent with neoplastic cell abnormalities possibly related to high turnover, resistance to apoptosis, osmotic stress and tumor tendency to use alternative energetic pathways such as glycolysis and ketogenesis.

Current concepts in the pathology and genetics of gliomas.

In recent years, there has been a marked improvement in our understanding of molecular genetics of gliomas. These advancements offer hope for development of tailored therapies targeting a tumor's unique molecular profile, and may also translate into improved classification and identification of newer prognostic markers. This review focuses on the neuropathological features of different types of glial neoplasms according to the World Health Organization classification, and the recent advances in their molecular biology with emphasis on the genetic mechanisms underlying tumor progression, diagnostic and prognostic markers and potential therapeutic targets.

Current concepts and newer developments in the treatment of malignant gliomas.

Primary malignant brain tumors account for only 2% of all adult cancers but they cause a disproportionately high cancer-related disability and death. Survival of malignant glioma patients has changed only modestly over the past three decades despite the emergence of new treatment strategies for these tumors. In this review, we describe the standard treatment modalities for malignant glioma, which include surgery, radiation therapy and chemotherapy, as well as the status of novel therapies that have been developed to target various aspects of glioma cell biology. We also address this issue of drug delivery as a factor limiting the efficacy of systemic administration of therapeutics and attempts to overcome this barrier. Further progress towards a cure for malignant gliomas will require a greater understanding of the underlying mechanisms driving the growth, and resistance to therapy, of these challenging tumors.

Mixed oligodendroglioma - meningioma: a rare collision tumour

A case of a very rare intra-axial brain tumour, consisting of components - maliganant meniongioma, oligodendroglioma and astrocytoma in a 36-year-old man, is described. A review of literature regarding its pathogenesis is presented and a classification for such tumours is proposed to identify pathologically different subgroups among them as they do not belong to a homogenous variety and comparison of different subgroups in not worthwhile

Espectroscopia multivoxel com tempo de eco curto: a razão colina/N-acetil-aspartato e a graduação dos astrocitomas cerebrais / Multivoxel spectroscopy with short echo time: choline/N-acetyl-aspartate ratio and the grading of cerebral astrocytomas

Avaliou-se a relação colina/N-acetil-aspartato (Co/NAA), obtida pela espectroscopia multivoxel com tempo de eco (TE) curto, na graduação histológica dos astrocitomas encefálicos (graus I, II e III-IV), comparando com o parênquima cerebral normal. Observou-se aumento significativo (p<0,05) das relações médias de Co/NAA nos três grupos de astrocitomas estudados em relação ao tecido normal, havendo tendência de elevação com o aumento da graduação, sem significância estatística, que correspondeu a: 0,53±0,24 no grupo controle, 1,19±0,49 no grau I, 1,58±0,65 no grau II e 5,13±8,12 no grupo de alto grau (graus III-IV). Houve aumento da relação Co/NAA em 4/5 (80 por cento) dos pacientes com grau I, 5/6 (83 por cento) com grau II e 10/20 (50 por cento) com graus III e IV. Concluiu-se que a espectroscopia multivoxel com TE curto pode ser usada na discriminação entre o parênquima normal e o tecido neoplásico. Entretanto, nem todo tecido neoplásico estudado apresentou aumento da relação Co/NAA, principalmente o grupo com maior malignidade.

The choline/N-acetyl-aspartate (Cho/NAA) ratio, obtained by the multivoxel spectroscopy with short echo time (TE), was evaluated, in the histological grading of the brain astrocytomas (grades I, II and III-IV) in comparison with the normal cerebral parenchyma. A significant increase (p<0.05) in the average ratios of Cho/NAA was observed in the three astrocytoma groups studied in relation to normal tissue, having a tendency to increase with the increase in grading, without any statistic significance, which corresponded to: 0.53±0.24 in the control group, 1.19±0.49 in grade I, 1.58±0.65 in grade II and 5.13±8.12 in the high grade group (grades III-IV), with variation in the values encountered. There was an increase in the Cho/NAA ratio in 4/5 (80 percent) in grade I, 5/6 (83 percent) in grade II and 10/20 (50 percent) in grades III and IV. We conclude that multivoxel spectroscopy with short TE can be used in discriminating between normal parenchyma and neoplasm tissue. However, not all neoplasm tissue studied presented an increase in Cho/NAA, especially in the group with higher grade of malignancy.

Análisis de 50 casos de tumores hipofisiarios operados / Analisys of 55 cases in operated pituitary tumors

Se presenta el análisis de 50 casos de tumores hipofisiarios operados en el Servicio de Neurocirugía de Valdivia, tanto por vía subfrontal, como por vía transesfenoidal, sus características clínicas, radiológicas, complicaciones, evolución y resultados. Se hace hincapié en las dificultades y facilidades que ofrecen ambas vías, acentuadas con los problemas que presenta la Neurocirugía en provincias.

Correlation of glial fibrillary acidic protein [GFAP] with grading of the neuroglial tumors

To determine the distribution of glial fibrillary acidic protein [GFAP] in human neuroglial tumours and its correlation with histologic grading. Analytical. Postgraduate Medical Institute, Lahore, on the cases from 1999 to 2001. Materials and Methods: Fifty formalin fixed paraffin-embedded tissue blocks were obtained. Two sections from each block were taken. One was stained with heamatoxylin-eosin stain while second for GFAP that is the unlabelled antibody immunoperoxidase [peroxidase ' antiperoxidase PAP] method was used. The non-neoplastic brain tissue was used as positive control, while cases reported medulloblastoma tumour was used as negative control. We applied a scoring scale 0 to 3+, to evaluate its correlation with the grade of tumour. In positive control only the cell process and perikaryons of fibrous astrocytes was stained. The 35 cases of various grade astrocytoma showed a varying intensity of GFAP staining. Similarly, 3 cases of glioblastoma multiforme, 2 cases of sub-ependymal giant cell astrocytoma, 2 cases of pleomorphic xanthoastrocytoma, 2 out of 4 cases of ependymoma and the case of oligoastrocytoma showed a positive reaction. The stain was more intense over processes than in perikaryons, with the exception of gemistocytic astrocytomas and the giant cells in glioblastoma multiforme, which showed an equally intense stain over perikaryons and processes. Comparison of the histological grade with GFAP score was significantly higher in high grade tumour when compared with tumour of grade I [p<0.001]. In astrocytic neoplasms the number of GFAP positive cells and the intensity of the stain were directly proportional to the degree of malignancy. All the 3 cases of oligodendroglioma showed a negative reaction to GFAP. Only astrocytic component was positive which are poorly visualize by H and E stain. The GFAP score shows significant relation with the present WHO grading system of glial tumours. GFA protein is specific for glial cells and it is useful to diagnose those glial tumours which are difficult to be identified by heamatoxylin-eosin stain or due to rare or unusual site

Primary central nervous system lymphoma: experience of 46 cases with review of literature.

Primary central nervous system lymphomas (PCNSL) constitutes only 1.0 to 1.5% of all brain tumors. Their incidence has gone up over tenfold in the last 25 years. Though, there has been an association of PCNSL with acquired immune deficiency syndrome (AIDS), yet the increased incidence of PCNSL appears to be real and unrelated to AIDS and organ transplantation. This increased incidence could be because of improvement in diagnostic technology and practice. The outcome remains gloomy despite surgical resection, radiotherapy and intensive adjuvant chemotherapy regimens, as majority of the patients succumb to the disease, with only 30-40% survival in patients under 70 years of age.

Gliomas múltiplos: casos ilustrativos de quatro formas de apresentação / Multiple gliomas: illustrative cases of 4 different presentations

Os gliomas múltiplos são relativamente raros e podem ser classificados didaticamente de acordo com: a) a época da apresentação, em precoces (quando presentes desde o diagnóstico inicial) ou tardios (quando presentes durante a evolução); e b) as características dos exames de imagem, em multifocais (quando há evidência de contiguidade das lesões) ou multicêntricos (quando não é possível identificar contiguidade das lesões). Entre os 212 pacientes com diagnóstico anatomopatológico de glioma, acompanhados prospectivamente no setor de neuro-oncologia de março/90 a setembro/99, 15 (7 por cento) apresentaram lesões múltiplas. Descrevemos 4 casos característicos de cada uma das possíveis apresentações: multicêntrico precoce, multicêntrico tardio, multifocal precoce e multifocal tardio, com ênfase nas características de imagem e possíveis diagnósticos diferenciais. O diagnóstico diferencial das lesões múltiplas no sistema nervoso central inclui doenças inflamatórias e infecciosas, além de metástases. A possibilidade de tratar-se de tumores de origem glial, entretanto, deve ser sempre lembrada, mesmo naqueles pacientes com diagnóstico de neoplasia sistêmica conhecida, conforme já descrito na literatura. O diagnóstico histológico se impõe, uma vez que as características de imagem não permitem diagnóstico de certeza.

Estudio estructural comparativo de los blastomas gliales del sistema nervioso central / Comparative structural study of the glial blastomas of the central nervous system

El OBJETIVO de nuestro trabajo es comparar 2 métodos diagnósticos, y demostrar las semejanzas de las distintas Clasificaciones de los Tumores Gliales del Sistema Nervioso Central. Se realizaron técnicas de inmunomarcación para proteína gliofibrilar ácida (GFAP), e impregnaciones argénticas especiales para confrontar los hallazgos según las últimas interpretaciones histogenéticas. Estudiamos 95 Gliomas con hematoxilina-eosina y técnicas argénticas, y en 58 casos tomados al azar realizamos además la técnica para GFAP. Con ambos métodos obtuvimos resultados iguales en el diagnóstico de tumores gliales cuyas células poseen gliofibrillas: Glioepiteliomas (Ependimonas), Glioblastomas, Astroblastomas y Astrocitomas. En los Oligodendrogliomas cuyas células no poseen gliofibrillas pero sí microtúbulos, las técnicas argénticas marcaron estas células y sus prolongaciones, no así la técnica para GFAP. Hay semejanzas al comparar la Clasificación de Del Río Horttega-Polak con la de la OMS y la de otros autores, en lo referente a los Gliomas. Sólo hay diferencias en la nomenclatura de algunos tumores o en su interpretación histogenética, que no son sustanciales y están limitados, que no son sustanciles y están limitados al "Espongioblastoma Polar" y al "Gliosarcoma". Por lo tanto, creemos que la revalorización de la Clasificación de Del Río Hortega-Polak está justificada.