Odontogenic Cysts and Tumours Reclassified by WHO 2022: A 10-Year Retrospective Histopathology Record Review

Odontogenic cysts and tumours form a large part of the jaw lesions reported by any oral pathology department. Their relative frequency differs between countries and even between regions of India, and the WHO Classification of Head and Neck Tumours, 5th edition (2022) has changed how several entities are grouped — for example, odontogenic keratocyst is listed with cysts, and newer entities such as adenoid ameloblastoma have been added. Departments therefore need their own updated data.

This project is a retrospective, record-based descriptive study (case series) of all odontogenic cysts and tumours diagnosed in the Department of Oral and Maxillofacial Pathology of a dental college over a ten-year period. The student reviews the biopsy register and histopathology reports, extracts age, gender, site, clinical and radiographic presentation and final diagnosis, and reclassifies every case under WHO 2022. Archived haematoxylin and eosin (H&E) slides of cases with ambiguous or outdated diagnoses are re-examined with the guide.

The analysis reports the relative frequency of each cyst and tumour, the ratio of cysts to tumours, age and gender distribution, site preference (maxilla vs mandible, anterior vs posterior) and histological variants of ameloblastoma, using Excel and SPSS with chi-square tests. Findings are compared with published Indian and international series. The project fits the DCI BDS optional research slot and can be proposed as an ICMR-STS study, and it builds exactly the knowledge examiners expect in oral pathology.

Abstract

A retrospective descriptive study will be conducted on all odontogenic cysts and tumours recorded in the biopsy archive of a dental college oral pathology department over ten years. Cases will be reclassified according to the WHO Classification of Head and Neck Tumours, 5th edition (2022). Demographic, clinical, radiographic and histopathological data will be analysed to determine relative frequency and distribution, and results will be compared with published studies.

Introduction

Odontogenic lesions arise from tooth-forming tissues — the epithelium of the dental lamina, reduced enamel epithelium and cell rests, and odontogenic ectomesenchyme. Cysts such as radicular, dentigerous and odontogenic keratocyst are common; tumours such as ameloblastoma, odontoma and adenomatoid odontogenic tumour are rarer but clinically important because of recurrence and local aggressiveness. Knowing the local pattern helps clinicians form differential diagnoses and helps departments plan teaching.

Review and gap

Indian retrospective series report radicular cyst as the most common odontogenic cyst and ameloblastoma or odontoma as the most common tumour, with regional differences. Most published series used the 2005 or 2017 WHO classifications. Few have applied the 2022 classification, and many do not re-review slides where diagnostic terminology has changed.

Proposed work

• Retrieve ten years of biopsy records and select odontogenic cysts and tumours.
• Extract data on a structured sheet and reclassify under WHO 2022.
• Re-review slides where needed with the guide.
• Describe and compare distributions statistically.

Expected outcome

The study will produce an updated frequency table of odontogenic cysts and tumours under WHO 2022, age- and site-wise distributions, a list of reclassified entities, and a set of representative photomicrographs from the department's own archive that can be used for undergraduate teaching and future research.

Feasibility

• Data: the department maintains a biopsy register, reports and slide archive.
• Time: extraction and re-review in six weeks; analysis and writing in the remaining weeks.
• Cost: negligible — existing records and microscopes.
• Ethics: IEC approval with waiver of consent for anonymised archival material.

The oral pathology department of the college reports hundreds of biopsies each year, but its records of odontogenic cysts and tumours have never been analysed as a whole. Diagnoses were made under older WHO classifications, so terms such as keratocystic odontogenic tumour, calcifying cystic odontogenic tumour and certain ameloblastoma subtypes no longer match current nomenclature. Clinicians and students therefore lack local data on which lesions are most common, in which age groups and at which sites.

This study aims to determine the relative frequency and demographic and site distribution of odontogenic cysts and tumours over ten years, reclassify all cases according to WHO 2022, and compare the findings with Indian and international literature, giving the department an updated, evidence-based profile for diagnosis and teaching.

In scope

• All histopathologically confirmed odontogenic cysts and tumours in the departmental archive for the ten-year period.
• Demographic, clinical, radiographic (as recorded) and histological data; reclassification under WHO 2022; re-review of selected slides.
• Descriptive statistics and chi-square comparisons.

Out of scope

• Non-odontogenic cysts and tumours, reactive lesions and malignancies of non-odontogenic origin.
• Immunohistochemistry or molecular testing (for example, BRAF V600E in ameloblastoma).
• Recurrence and follow-up outcome, which the records do not capture reliably.

Study design: retrospective, record-based descriptive study (case series).

Setting and period: Department of Oral and Maxillofacial Pathology of a dental college; records for a ten-year period; 12 weeks for approvals, extraction, re-review, analysis and report.

Sample: all eligible cases in the period (complete enumeration) — no sampling, so the sample-size question becomes a statement of the total cases found, which is typical for a record-based series.

Inclusion criteria: cases with a final histopathological diagnosis of an odontogenic cyst or odontogenic tumour, with available report and demographic data.

Exclusion criteria: inconclusive or inadequate biopsies, recurrent lesions already counted in the period (each patient counted once, at first diagnosis), non-odontogenic lesions, and cases with missing reports.

Data extraction: study number, year, age, gender, site (maxilla/mandible; anterior/premolar/molar/ramus), clinical presentation, radiographic description as recorded, original diagnosis, WHO 2022 diagnosis, histological variant.

Reclassification: each original diagnosis mapped to WHO 2022 terms by the student and verified by the guide; cases where the report is insufficient for reclassification have archived H&E slides re-examined jointly under a microscope; unresolved cases recorded as such.

Ethics: IEC approval with waiver of consent for retrospective anonymised archival material; permission from the Head of Department; no names, OP numbers or identity details transcribed; ICMR National Ethical Guidelines (2017), including the section on use of stored biological material.

Statistical analysis: Excel and SPSS. Frequencies and percentages; mean ± SD age; cyst-to-tumour ratio; male-to-female ratio; chi-square test for gender and jaw distribution against expected equal distribution and between lesion groups; p < 0.05.