5th edition WHO odontogenic tumours

Page 1: Overview of Changes in WHO Classification (2022)

Introduction to the Update

  • The 5th edition of the WHO Classification of Head and Neck Tumours focuses on Odontogenic and Maxillofacial Bone Tumours, addressing the rapid advancements in molecular investigations and their clinical relevance.

  • Significant updates have been made since the 2017 edition, which included the introduction of "Essential" and "Desirable diagnostic features" for each entity to aid in diagnosis.

Key Updates in Classification

  • New entities and changes include:

    • Surgical Ciliated Cyst: Added to odontogenic cysts.

    • Adenoid Ameloblastoma: Newly recognized benign epithelial odontogenic tumour.

    • Segmental Odontomaxillary Dysplasia: Introduced in the group of fibrous lesions.

    • Rhabdomyosarcoma with TFCP2 Rearrangement: A malignant jawbone tumour with unique genetic aberrations.

  • Deleted entities:

    • Melanotic neuroectodermal tumour of infancy, osteoid osteoma, and solitary plasmacytoma of bone.

Potential Impact on Diagnosis and Treatment

  • The manuscript presents an overview of critical findings that enhance diagnostic processes and insights into both classification logic and potential treatment approaches based on molecular findings.

Page 2: Structural Changes and New Definitions in Classification

General Reorganization

  • The 2022 edition emphasizes consensus definitions and clearer diagnostic features, while most entities retain their original structural classifications.

  • New definitions include Essential and Desirable Diagnostic Features to standardize descriptions.

Notable New Definitions

  • Rhabdomyosarcoma of Bone: Defined by molecular findings related to TFCP2.

  • Surgical Ciliated Odontogenic Cyst: A rare cyst characterized by respiratory epithelium entrapment.

  • Calcifying Odontogenic Cyst (COC): Defined by the presence of characteristic ghost cells; the previous separation of odontoma-associated COCs has been removed.

  • Glandular Odontogenic Cyst (GOC): Criteria for diagnosis have been adjusted to reflect characteristic features without strict criteria.

  • Odontogenic Keratocyst (OKC): Maintained its classification; genetic modifications linked to PTCH1 have been identified as significant.

Page 3: Comparison of 2022 and 2017 Classifications

Table of Changes

  • Presented side-by-side comparison of lesions categorized under Cysts of the Jaws, Odontogenic Tumours, Giant Cell Lesions, and Bone Cysts between 2022 and 2017 editions.

Highlighted Changes

  • New listings and definitions for odontogenic tumours illustrate the evolved understanding and categorization of these entities, improving diagnostic clarity.

Page 4: Odontogenic Tumours – Key Features

Benign Odontogenic Tumours Updates

  • Adenomatoid Odontogenic Tumour (AOT): Commonly linked with KRAS mutations, although not associated with clinico-pathological traits.

  • Various classification updates have been made to distinguish between specific odontogenic tumours.

Historical Context

  • Discussions clarified the diagnostic landscape and addressed why certain tumours were reformulated, focusing on genetic and morphological characteristics.

Page 5: Subtypes in Calcifying Epithelial Odontogenic Tumour (CEOT)

Histopathological Subtypes

  • CEOT now involves three subtypes based on histopathological characteristics.

  • Various gene mutations have been linked to CEOT’s pathogenesis, although their clinical implications are still being studied.

Ameloblastoma Classification

  • The reintroduction of the term “conventional” for ameloblastoma reflects changes in how these tumours are categorized and treated.

Page 6: Adenoid Ameloblastoma and Characteristics

Overview of Adenoid Ameloblastoma

  • Recognized as a distinct entity, showing cribriform architecture and often containing dentinoid.

  • Exhibits significant histopathological overlap with other odontogenic tumours.

Biological Behavior

  • Classified as aggressive, with specific markers that could influence treatment planning and outcomes.

Page 7: Malignant Odontogenic Tumours Updates

Ameloblastic Carcinoma (AMCa)

  • Defined as a primary odontogenic carcinoma, it retains its high-risk status as a malignant entity.

Genetic Influence on Diagnosis

  • Differential diagnoses include various tumours with overlapping features, highlighting the complexity in classification and clinical management.

Page 8: Bone and Cartilage Tumours and Genetic Influences

Overview of Genetic Aberrations

  • Changes in definitions highlight specific genetic variants seen in tumours, which could lead to more targeted therapies in the future.

Emphasis on Classification Evolution

  • Detailed focus on both benign and malignant maxillofacial tumours explains structural and nomenclature changes since past editions.

Page 9: Fibro-Osseous Lesions and Tumour Subtypes

Variations and Classifications

  • New subtypes introduced within fibro-osseous lesions, enhancing the diagnostic clarity and treatment strategies available.

Page 10: Benign Maxillofacial Bone and Cartilage Tumours

Overview of Major Changes

  • Classifications and genetic findings emphasized in several benign tumours outline key differentiating factors crucial for diagnosis and treatment planning.

Page 11: Malignant Tumours and Emerging Classifications

Rhabdomyosarcoma with TFCP2 Rearrangement

  • Introduced as a new tumour type with distinct genetic characteristics and clinical implications.

Summary of Prognostic Factors

  • Detailed prognostic insights emphasize the clinical importance of genetic findings and their impact on patient outcomes.

Page 12: Research Directions and Future Studies

Highlights of Research Needs

  • The manuscript underscores the necessity for ongoing research to confirm speculations regarding categorization and treatment approaches based on emerging genetic data.