(50) Odontogenic Myxoma: An Institutional Experience

Abstract: Problem:Odontogenic myxoma (OM) is benign gnathic tumor speculated to be odontogenic ectomesenchymal in origin. As these tumors are quite rare, single institution experience in diagnosis, handling, and treatment is limited. The aim of this research was to characterize our single institutional experience with OM.Materials and methods: Archival files within our Pathology Department were searched for OM diagnosed in patients ≥ 4 years of age within the time frame spanning 2000 to 2023. Patient charts were accessed in the institutional electronic medical record. Data abstraction included patient demographics, including age, sex, tumor characteristics, biopsy diagnosis, treatment administered, use of intraoperative consultation, margin status, recurrence, and follow-up. Methods of data analysis:Statistical analysis included provision of average relative to patient age, lesion size, and years of follow-up. Remaining analysis was descriptive in nature, relating to the small sample size.ResultsSixty-two cases of OM were identified from 3 sources within our single pathology archival database: pathology case material submitted to our institutional pathology service by clinicians within the community operating outpatient clinics; our academic institution-based patient cohort; and cases referred to our institutional pathologists in consultation from external institution for diagnostic opinion. The entire cohort consisted of 42 females and 20 males, with an average age of 47 (range 4-71 years). The 62 patients were further stratified into two 12-year cohorts to evaluate differences in characteristics (Table 1). Over time, patients with OM were more likely to be within the second to fourth decade of life, female, with a mandibular lesion. In patients undergoing biopsy in the outpatient community setting prior to further surgical management, there appears to be a risk (~20%) of misdiagnosis of OM as another benign lesion. This risk was present within both cohorts. Curettage represented the most frequent treatment early on in our experience, with the number of resected tumors remaining relatively stable over time. Intraoperative consultation remains infrequently used as a surgical adjunct in our experience. In resected specimens, the rate of negative surgical margins remained unchanged over time (Figure, macroscopic appearance of OM, CT appearance of OM). While the rate of ambiguous margins decreased, the rate of positive margins increased in our more recent cohort. Outcomes data: The trend toward a reduction in ambiguous margins and an increase in microscopic-positive margins in the recent time cohort may have been influenced by the larger size of tumors treated and/or improved macroscopic specimen handling in the pathology lab and/or specimen sampling over time. Although patient attendance for follow up appointments tends to wane over time, the low rate of recurrence in both time cohorts, despite extension beyond bone into adjacent submucosal planes suggests that overall, OM has relatively low biologic potential.

Conclusion: The demographics of patients and characteristics of OM appear relatively stable over our study period. Patients with larger tumors are referred for treatment at our academic facility, and despite the large size, this tumor shows a good prognosis. We have identified a risk of misdiagnosis of OM when this tumor is sampled in an outpatient private clinical setting. Providing supplementary clinical and/or radiographic material may have a role in limiting this pitfall. Gross total excision in the form of meticulous curettage and/or surgical resection (even with microscopic positive margin status) may represent sufficient treatment for OM.ReferencesE Simon, M. Merkx, E.Vuhahula, D.Ngassapa, PJW Stoeling Odontogenic myxoma: a clinicopathological study of 33 cases Int J Oral Maxillofac Surg. 2004 Jun;33(4):333-7AM Banasser, M M Bawazir, M N Islam, I Bhattacharyya, D M Cohen, S G Fitzpatrick. Odontogenic Myxoma: A 23-Year Retrospective Series of 38 Cases. Head Neck Pathol2020 Dec;14(4):1021-1027

Representative Mandibular Resection of OM; Cohort 2
Cohort of Odontogenic Myxoma Over 23 Years