All Stories

  1. Identification of prognostic variables in patients with recurrent head and neck squamous cell carcinoma treated with salvage surgery: Implications for treatment with immunotherapy

    Article • Oral Oncology, April 2026, Elsevier

    Dr Xavier León

  2. Prognostic value of pretreatment peripheral blood biomarkers in patients with head and neck squamous cell carcinoma treated with chemo/bioradiotherapy

    Article • Revista de Oncología, May 2025, Springer Science + Business Media

    Dr Xavier León

  3. Relación de la infección por el virus del papiloma humano con la aparición de segundas neoplasias y su repercusión pronóstica en los pacientes con carcinoma de orofaringe

    Article • Acta Otorrinolaringológica Española, April 2025, Elsevier

    Dr Xavier León

  4. Transcriptional Expression of SLC2A3 and SDHA Predicts the Risk of Local Tumor Recurrence in Patients with Head and Neck Squamous Cell Carcinomas Treated Primarily with Radiotherapy or Chemoradiotherapy

    Article • International Journal of Molecular Sciences, March 2025, MDPI AG

    Dr Xavier León

  5. Análisis de la supervivencia de los pacientes con tumores malignos de cabeza y cuello diagnosticados durante la pandemia de COVID-19

    Article • Acta Otorrinolaringológica Española, February 2025, Elsevier

    Dr Xavier León

  6. Survival of patients with malignant head and neck tumors diagnosed during the COVID-19 pandemic

    Article • Acta Otorrinolaringologica (English Edition), February 2025, Elsevier

    Dr Xavier León

  7. Predictive capacity for local disease control of neogenin-1 (NEO1) transcriptional expression in patients with head and neck squamous cell carcinoma

    Article • Revista de Oncología, June 2024, Springer Science + Business Media

    Dr Xavier León

  8. Survivin/BIRC5 as a novel molecular effector at the crossroads of glucose metabolism and radioresistance in head and neck squamous cell carcinoma

    Article • Head & Neck, February 2024, Wiley

    Dr Xavier León

  9. External validation of the GETTEC algorithm for elective neck dissection in patients candidates for salvage total laryngectomy

    Article • Oral Oncology, February 2024, Elsevier

    Dr Xavier León

  10. External validation of the H‐index (host index) in patients with head and neck squamous cell carcinomas

    Article • Head & Neck, October 2022, Wiley

    Dr Xavier León

  11. Concordance of p16INK4a and E6*I mRNA among HPV-DNA-Positive Oropharyngeal, Laryngeal, and Oral Cavity Carcinomas from the ICO International Study

    Article • Cancers, August 2022, MDPI AG

    Dr Xavier León

  12. Prognostic capacity of the transcriptional expression of lactate dehydrogenase A in patients with head and neck squamous cell carcinoma

    Article • Head & Neck, August 2022, Wiley

    Dr Xavier León

  13. Prognostic value of transcriptional expression of fibronectin type III domain-containing 4 (FNDC4) in head and neck carcinoma patients treated with chemoradiotherapy

    Article • Revista de Oncología, June 2022, Springer Science + Business Media

    Dr Xavier León

  14. The extended SCIP flap: an anatomical and clinical study of a new SCIP flap design

    Article • Journal of Plastic Reconstructive & Aesthetic Surgery, June 2022, Elsevier

    Dr Xavier León

  15. Semaphorin-3F/Neuropilin-2 Transcriptional Expression as a Predictive Biomarker of Occult Lymph Node Metastases in HNSCC

    Article • Cancers, April 2022, MDPI AG

    Dr Xavier León

  16. A Novel CXCR4-Targeted Diphtheria Toxin Nanoparticle Inhibits Invasion and Metastatic Dissemination in a Head and Neck Squamous Cell Carcinoma Mouse Model

    Article • Pharmaceutics, April 2022, MDPI AG

    Dr Xavier León

  17. CXCR4-targeted nanotoxins induce GSDME-dependent pyroptosis in head and neck squamous cell carcinoma

    Article • Journal of Experimental & Clinical Cancer Research, February 2022, Springer Science + Business Media

    Dr Xavier León

  18. Relationship between the transcriptional expression of PIM1 and local control in patients with head and neck squamous cell carcinomas treated with radiotherapy

    Article • European Archives of Oto-Rhino-Laryngology, January 2022, Springer Science + Business Media

    Dr Xavier León

  19. Causes of long-term mortality in patients with head and neck squamous cell carcinomas

    Article • European Archives of Oto-Rhino-Laryngology, December 2021, Springer Science + Business Media

    Dr Xavier León

  20. Anatomic mapping of the collateral branches of the external carotid artery with regard to daily clinical practice

    Article • Annals of Anatomy - Anatomischer Anzeiger, November 2021, Elsevier

    Dr Xavier León

  21. Self-assembling protein nanocarrier for selective delivery of cytotoxic polypeptides to CXCR4+ head and neck squamous cell carcinoma tumors

    Article • Acta Pharmaceutica Sinica B, October 2021, Elsevier

    Dr Xavier León

  22. Predictive value of transcriptional expression of Krüppel-like factor-6 (KLF6) in head and neck carcinoma patients treated with radiotherapy

    Article • Revista de Oncología, June 2021, Springer Science + Business Media

    Dr Xavier León

  23. Succinate Pathway in Head and Neck Squamous Cell Carcinoma: Potential as a Diagnostic and Prognostic Marker

    Article • Cancers, April 2021, MDPI AG

    Dr Xavier León

  24. The Effect of Perioperative Blood Transfusions on Microvascular Anastomoses

    Article • Journal of Clinical Medicine, March 2021, MDPI AG

    Dr Xavier León

  25. The aspartate aminotransaminase/alanine aminotransaminase (De Ritis) ratio predicts sensitivity to radiotherapy in head and neck carcinoma patients

    Article • Head & Neck, March 2021, Wiley

    Dr Xavier León

  26. Oral cavity colon adenocarcinoma metastases: case report with surgical approach and review of more than 30 years literature

    Article • Oral and Maxillofacial Surgery, July 2020, Springer Science + Business Media

    Dr Xavier León

  27. Weighted lymph node ratio: New tool in the assessment of postoperative staging of the neck dissection in HPV ‐negative head and neck squamous cell carcinoma patients

    Article • Head & Neck, June 2020, Wiley

    Dr Xavier León

  28. Prognostic capacity of Systemic Inflammation Response Index (SIRI) in patients with head and neck squamous cell carcinoma

    Article • Head & Neck, November 2019, Wiley

    Dr Xavier León

  29. Indications and results of extended total laryngectomy with en-bloc resection of overlying cervical skin

    Article • European Archives of Oto-Rhino-Laryngology, July 2019, Springer Science + Business Media

    Dr Xavier León

  30. The combined use of EFS, GPX2, and SPRR1A expression could distinguish favorable from poor clinical outcome among epithelial‐like head and neck carcinoma subtypes

    Article • Head & Neck, January 2019, Wiley

    Dr Xavier León

  31. Competing mortality in oropharyngeal carcinoma according to human papillomavirus status

    Article • Head & Neck, December 2018, Wiley

    Dr Xavier León

  32. Effect of serpinE1 overexpression on the primary tumor and lymph node, and lung metastases in head and neck squamous cell carcinoma

    Article • Head & Neck, December 2018, Wiley

    Dr Xavier León

  33. Distinctive Expression and Amplification of Genes at 11q13 in Relation to HPV Status with Impact on Survival in Head and Neck Cancer Patients

    Article • Journal of Clinical Medicine, December 2018, MDPI AG

    Dr Xavier León

  34. Prognostic role of extracapsular spread in planned neck dissection after chemoradiotherapy

    Article • Head & Neck, October 2018, Wiley

    Dr Xavier León

  35. Impacto de la laringectomía total en la situación laboral

    Article • Acta Otorrinolaringológica Española, March 2018, Elsevier

    Dr Xavier León

  36. Prognostic value of CD45 transcriptional expression in head and neck cancer

    Article • European Archives of Oto-Rhino-Laryngology, November 2017, Springer Science + Business Media

    Dr Xavier León

  37. Prognostic relevance of insulin resistance on disease-free survival in head and neck squamous cell carcinomas: Preliminary results

    Article • Head & Neck, September 2017, Wiley

    Dr Xavier León

  38. Validation of the pathological classification of lymph node metastasis for head and neck tumors according to the 8th edition of the TNM Classification of Malignant Tumors

    Article • Oral Oncology, July 2017, Elsevier

    Dr Xavier León

  39. The prognostic value of pretreatment platelet count in patients with head and neck squamous cell carcinoma

    Article • Auris Nasus Larynx, June 2017, Elsevier

    Ms Cristina Valero, Dr Xavier León

  40. Relationship between response to induction chemotherapy and disease control in patients with advanced laryngeal carcinoma included in an organ preservation protocol

    Article • European Archives of Oto-Rhino-Laryngology, March 2017, Springer Science + Business Media

    Ms Cristina Valero, Dr Xavier León

  41. Human papillomavirus as prognostic marker with rising prevalence in neck squamous cell carcinoma of unknown primary: A retrospective multicentre study

    Article • European Journal of Cancer, March 2017, Elsevier

    Dr Xavier León

  42. Nasopharyngeal carcinoma: 30-year experience of a single institution in a non-endemic area

    Article • Revista de Oncología, January 2017, Springer Science + Business Media

    Dr Xavier León

  43. The role of HPV on the risk of second primary neoplasia in patients with oropharyngeal carcinoma

    Article • Oral Oncology, January 2017, Elsevier

    Dr Xavier León

  44. Nodules en cavité orale, pharynx et larynx

    Article • Annales françaises d Oto-rhino-laryngologie et de Pathologie Cervico-faciale, September 2016, Elsevier

    Dr Xavier León

  45. Oral cavity, pharynx and larynx nodules

    Article • European Annals of Otorhinolaryngology Head and Neck Diseases, September 2016, Elsevier

    Dr Xavier León

  46. Pretreatment count of peripheral neutrophils, monocytes, and lymphocytes as independent prognostic factor in patients with head and neck cancer

    Article • Head & Neck, August 2016, Wiley

    Ms Cristina Valero, Dr Xavier León

  47. Prognostic significance of extracapsular spread in isolated neck recurrences in head and neck squamous cell carcinoma patients

    Article • European Archives of Oto-Rhino-Laryngology, August 2016, Springer Science + Business Media

    Dr Xavier León

  48. uPA/uPAR and SERPINE1 in head and neck cancer: role in tumor resistance, metastasis, prognosis and therapy

    Article • Oncotarget, June 2016, Impact Journals, LLC

    Dr Xavier León

  49. Expression of the CXCL12/CXCR4 chemokine axis predicts regional control in head and neck squamous cell carcinoma

    Article • European Archives of Oto-Rhino-Laryngology, June 2016, Springer Science + Business Media

    Dr Xavier León

  50. Management of recurrent head and neck cancer: variables related to salvage surgery

    Article • European Archives of Oto-Rhino-Laryngology, May 2016, Springer Science + Business Media

    Dr Xavier León

  51. Expresión de Heat Shock Protein-90 (HSP-90) como factor predictor de la respuesta a radioterapia en pacientes con tumores de cabeza y cuello

    Article • Acta Otorrinolaringológica Española, May 2016, Elsevier

    Dr Xavier León

  52. Classification of parotidectomies: a proposal of the European Salivary Gland Society

    Article • European Archives of Oto-Rhino-Laryngology, February 2016, Springer Science + Business Media

    Professor Pavel Dulguerov, Professor Orlando Guntinas-Lichius, Dr Xavier León

  53. HPV Involvement in Head and Neck Cancers: Comprehensive Assessment of Biomarkers in 3680 Patients

    Article • JNCI Journal of the National Cancer Institute, January 2016, Oxford University Press (OUP)

    Dr Xavier León

  54. External validation of sTWEAK as a prognostic noninvasive biomarker for head and neck squamous cell carcinoma

    Article • Head & Neck, December 2015, Wiley

    Dr Xavier León

  55. CKMT1 and NCOA1 expression as a predictor of clinical outcome in patients with advanced-stage head and neck squamous cell carcinoma

    Article • Head & Neck, October 2015, Wiley

    Dr Xavier León

  56. Expression of IL-1α correlates with distant metastasis in patients with head and neck squamous cell carcinoma

    Article • Oncotarget, October 2015, Impact Journals, LLC

    Dr Xavier León

  57. Reconstrucción de defectos de cavidad oral con colgajos tipo FAMM (colgajo músculo-mucoso de arteria facial). Nuestra experiencia

    Article • Acta Otorrinolaringológica Española, September 2015, Elsevier

    Dr Xavier León

  58. Enhanced cell migration and apoptosis resistance may underlie the association between high SERPINE1 expression and poor outcome in head and neck carcinoma patients

    Article • Oncotarget, August 2015, Impact Journals, LLC

    Dr Xavier León

  59. Salvage surgery after local recurrence in patients with head and neck carcinoma treated with chemoradiotherapy or bioradiotherapy

    Article • Auris Nasus Larynx, April 2015, Elsevier

    Dr Xavier León

  60. Tratamiento quirúrgico de los carcinomas escamosos de cabeza y cuello en España durante el periodo 2006-2011

    Article • Acta Otorrinolaringológica Española, March 2015, Elsevier

    Dr Xavier León

  61. Management of Sinonasal Mucosal Melanomas and Comparison of Classification Staging Systems

    Article • American Journal of Rhinology and Allergy, January 2015, SAGE Publications

    Dr Xavier León

  62. Parotid Incidentaloma Identified by Positron Emission/Computed Tomography: When to Consider Diagnoses Other than Warthin Tumor

    Article • International Archives of Otorhinolaryngology, December 2014, Thieme Publishing Group

    Dr Xavier León

  63. Prostacyclin-synthase expression in head and neck carcinoma patients and its prognostic value in the response to radiotherapy

    Article • The Journal of Pathology, December 2014, Wiley

    Mercedes Camacho, Dr Xavier León

  64. Stomal recurrence in head and neck cancer patients with temporary tracheostomy

    Article • Auris Nasus Larynx, October 2014, Elsevier

    Dr Xavier León

  65. Reply to letter to the editor

    Article • Head & Neck, July 2014, Wiley

    Dr Xavier León

  66. Etiología y tratamiento de la parálisis laríngea: estudio retrospectivo de 108 pacientes

    Article • Acta Otorrinolaringológica Española, July 2014, Elsevier

    Dr Xavier León

  67. Low blood levels of sTWEAK are related to locoregional failure in head and neck cancer

    Article • European Archives of Oto-Rhino-Laryngology, May 2014, Springer Science + Business Media

    Dr Xavier León

  68. High RAB 25 expression is associated with good clinical outcome in patients with locally advanced head and neck squamous cell carcinoma

    Article • Cancer Medicine, October 2013, Wiley

    Dr Xavier León

  69. Elective treatment of the neck for second primary tumors of the head and neck

    Article • European Archives of Oto-Rhino-Laryngology, July 2013, Springer Science + Business Media

    Dr Xavier León

  70. Adherencia crónica al humidificador de traqueostoma en pacientes laringectomizados

    Article • Acta Otorrinolaringológica Española, July 2013, Elsevier

    Dr Xavier León

  71. Inclusion of Extracapsular Spread in the pTNM Classification System

    Article • JAMA Otolaryngology–Head & Neck Surgery, May 2013, American Medical Association (AMA)

    Dr Xavier León

  72. Prognostic role of MMP-9 expression in head and neck carcinoma patients treated with radiotherapy or chemoradiotherapy

    Article • Oral Oncology, April 2013, Elsevier

    Dr Xavier León

  73. Endonasal Endoscopic Scalpel-Forceps Dacryocystorhinostomy vs Endocanalicular Diode Laser Dacryocystorhinostomy

    Article • European Journal of Ophthalmology, January 2013, SAGE Publications

    Dr Xavier León

  74. Delayed carotid blow-out syndrome: a new complication of chemoradiotherapy treatment in pharyngolaryngeal carcinoma

    Article • The Journal of Laryngology & Otology, September 2012, Cambridge University Press

    Dr Xavier León

  75. Prognostic factors in head and neck squamous cell carcinoma: Comparison of CHAID decision trees technology and cox analysis

    Article • Head & Neck, June 2012, Wiley

    Dr Xavier León

  76. Gene expression signatures and molecular markers associated with clinical outcome in locally advanced head and neck carcinoma

    Article • Carcinogenesis, June 2012, Oxford University Press (OUP)

    Dr Xavier León

  77. Overexpression of the nuclear factor-kappa B (p65) in association with local failure in patients with head and neck carcinoma undergong radiotherapy or chemoradiotherapy

    Article • Head & Neck, March 2012, Wiley

    Dr Xavier León

  78. Comparison of Chi-Squared Automatic Interaction Detection Classification Trees vs TNM Classification for Patients With Head and Neck Squamous Cell Carcinoma

    Article • Archives of Otolaryngology - Head and Neck Surgery, March 2012, American Medical Association (AMA)

    Dr Xavier León

  79. Second, third, and fourth head and neck tumors. A progressive decrease in survival

    Article • Head & Neck, February 2012, Wiley

    Dr Xavier León

  80. Interaction between head and neck squamous cell carcinoma cells and fibroblasts in the biosynthesis of PGE2

    Article • Journal of Lipid Research, February 2012, American Society for Biochemistry & Molecular Biology (ASBMB)

    Dr Xavier León

  81. Sarcomas de cabeza y cuello. Nuestra experiencia

    Article • Acta Otorrinolaringológica Española, November 2011, Elsevier

    Dr Xavier León

  82. Total or subtotal glossectomy with microsurgical reconstruction: Functional and oncological results

    Article • Microsurgery, September 2011, Wiley

    Dr Xavier León

  83. Tumor cells induce COX-2 and mPGES-1 expression in microvascular endothelial cells mainly by means of IL-1 receptor activation

    Article • Microvascular Research, May 2011, Elsevier

    Dr Xavier León

  84. Extended deep inferior epigastric artery perforator flap for head and neck reconstruction: A clinical experience with 100 patients

    Article • Head & Neck, November 2010, Wiley

    Dr Xavier León

  85. Salvage surgery after locoregional failure in head and neck carcinoma patients treated with chemoradiotherapy

    Article • European Archives of Oto-Rhino-Laryngology, August 2010, Springer Science + Business Media

    Dr Xavier León

  86. Risk of third and fourth tumors in patients with head and neck cancer

    Article • Head & Neck, February 2010, Wiley

    Dr Xavier León

  87. Management of Sinonasal Inverted Papillomas and Comparison of Classification Staging Systems

    Article • American Journal of Rhinology and Allergy, January 2010, SAGE Publications

    Dr Xavier León

  88. Parotidectomías en tumores benignos: clasificación «Sant Pau» de la extensión de la resección

    Article • Acta Otorrinolaringológica Española, January 2010, Elsevier

    Dr Xavier León

  89. Tratamiento endoscópico combinado vs. abierto en el divertículo de Zenker

    Article • Acta Otorrinolaringológica Española, November 2009, Elsevier

    Dr Xavier León

  90. Resultados de un protocolo de preservación de órgano en pacientes con tumores localmente avanzados de la laringe

    Article • Acta Otorrinolaringológica Española, June 2009, Elsevier

    Dr Xavier León

  91. Ceratocricoid muscle: An embryological and anatomical study

    Article • Clinical Anatomy, May 2009, Wiley

    Dr Xavier León

  92. Influence of the persistence of tobacco and alcohol use in the appearance of second neoplasm in patients with a head and neck cancer. A case–control study

    Article • Cancer Causes & Control, December 2008, Springer Science + Business Media

    Dr Xavier León

  93. Prostaglandin E2pathway in head and neck squamous cell carcinoma

    Article • Head & Neck, September 2008, Wiley

    Mercedes Camacho, Dr Xavier León

  94. Ku70 predicts response and primary tumor recurrence after therapy in locally advanced head and neck cancer

    Article • International Journal of Cancer, September 2008, Wiley

    Dr Xavier León

  95. Colgajo de pectoral mayor

    Article • Acta Otorrinolaringológica Española, July 2008, Elsevier

    Dr Xavier León

  96. Overview of the efficacy of cetuximab in recurrent and/or metastatic squamous cell carcinoma of the head and neck in patients who previously failed platinum-based therapies

    Article • Cancer, June 2008, Wiley

    Dr Xavier León

  97. Trasplante de la laringe: ¿una opción terapéutica para el siglo XXI? Revisión de la literatura

    Article • Acta Otorrinolaringológica Española, March 2008, Elsevier

    Dr Xavier León

  98. Potential Structures That Could Be Confused With a Nonrecurrent Inferior Laryngeal Nerve: An Anatomic Study

    Article • The Laryngoscope, January 2008, Wiley

    Dr Xavier León

  99. Recurrent laryngeal squamous cell carcinoma: rTNM versus composite laryngeal recurrence staging system. Proposal for a modification of the CLRSS to improve patient classification

    Article • Head & Neck, January 2008, Wiley

    Dr Xavier León

  100. Modalidades de preservación de órgano en carcinomas de laringe e hipofaringe

    Article • Acta Otorrinolaringológica Española, December 2007, Elsevier

    Dr Xavier León

  101. External validation of a risk group defined by recursive partitioning analysis in patients with head and neck carcinoma treated with surgery and postoperative radiotherapy

    Article • Head & Neck, September 2007, Wiley

    Dr Xavier León

  102. Supracricoid laryngectomy as salvage surgery after failure of radiation therapy

    Article • European Archives of Oto-Rhino-Laryngology, February 2007, Springer Science + Business Media

    Dr Xavier León

  103. Organ Preservation in Laryngeal and Hypopharyngeal Cancer

    Article • Acta Otorrinolaringologica (English Edition), January 2007, Elsevier

    Dr Xavier León

  104. A Retrospective Analysis of the Outcome of Patients with Recurrent and/or Metastatic Squamous Cell Carcinoma of the Head and Neck Refractory to a Platinum-based Chemotherapy

    Article • Clinical Oncology, September 2005, Elsevier

    Dr Xavier León

  105. Metachronous second primary tumours in the aerodigestive tract in patients with early stage head and neck squamous cell carcinomas

    Article • European Archives of Oto-Rhino-Laryngology, May 2005, Springer Science + Business Media

    Dr Xavier León

  106. Comparison of the Radiation Therapy Oncology Group recursive partitioning classification and Union Internationale Contre le Cancer TNM classification for patients with head and neck carcinoma

    Article • Head & Neck, March 2005, Wiley

    Dr Xavier León

  107. Incidence and Significance of Clinically Unsuspected Thyroid Tissue in Lymph Nodes Found During Neck Dissection in Head and Neck Carcinoma Patients

    Article • The Laryngoscope, March 2005, Wiley

    Dr Xavier León

  108. Variability in Nerve Patterns of the Adductor Muscle Group Supplied by the Recurrent Laryngeal Nerve

    Article • The Laryngoscope, February 2005, Wiley

    Dr Xavier León

  109. Laryngeal cancer in non-smoking and non-drinking patients

    Article • Acta Oto-Laryngologica, August 2004, Taylor & Francis

    Dr Xavier León

  110. Is dissection of level V necessary in patients with T2–T4N0 supraglottic cancer?

    Article • The Journal of Laryngology & Otology, March 2004, Cambridge University Press

    Dr Xavier León

  111. Results of an organ preservation protocol with induction chemotherapy and radiotherapy in patients with locally advanced laryngeal carcinoma

    Article • European Archives of Oto-Rhino-Laryngology, February 2004, Springer Science + Business Media

    Dr Xavier León

  112. Variability of the Nerve Supply Patterns of the Human Posterior Cricoarytenoid Muscle

    Article • The Laryngoscope, April 2003, Wiley

    Dr Xavier León

  113. Is the External Laryngeal Nerve an Exclusively Motor Nerve? The Cricothyroid Connection Branch

    Article • The Laryngoscope, March 2003, Wiley

    Dr Xavier León

  114. The effect of waiting time on local control and survival in head and neck carcinoma patients treated with radiotherapy

    Article • Radiotherapy and Oncology, March 2003, Elsevier

    Dr Xavier León

  115. Second Primary Tumors in Head and Neck Cancer Patients

    Article • Acta Oto-Laryngologica, October 2002, Taylor & Francis

    Dr Xavier León, Professor Patrick James Bradley

  116. Results of salvage surgery for local or regional recurrence after larynx preservation with induction chemotherapy and radiotherapy

    Article • Head & Neck, August 2001, Wiley

    Dr Xavier León

  117. Selective dissection of levels II-III with intraoperative control of the upper and middle jugular nodes: A therapeutic option for the no neck

    Article • Head & Neck, May 2001, Wiley

    Dr Xavier León

  118. An anatomical study of anastomoses between the laryngeal nerves

    Article • The Laryngoscope, June 1999, Wiley

    Dr Xavier León

  119. Foramen Thyroideum: A Comparative Study in Embryos, Fetuses, and Adults

    Article • The Laryngoscope, August 1997, Wiley

    Dr Xavier León