Mandible / maxilla
Benign tumors / tumorlike conditions
Myxoma

Author: Anthony Martinez, M.D.
Editor: Kelly Magliocca D.D.S., M.P.H.

Revised: 5 December 2017, last major update November 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Myxoma mandible [title]

Cite this page: Martinez, A. Myxoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillamyxoma.html. Accessed December 18th, 2017.
Definition / general
  • Benign odontogenic neoplasm characterized by bland, spindled to stellate cells set in myxoid stroma
Essential features
  • Benign odontogenic myxoid lesion composed of spindled to stellate cells
  • Third most frequent odontogenic tumor (after odontoma and ameloblastoma)
  • Recurrence rate ~25%
Terminology
  • Odontogenic myxoma
  • Odontogenic myxofibroma
  • Odontogenic fibromyxoma
Epidemiology
  • Most cases diagnosed in 2nd - 4th decades but wide age range of occurrence (between 1 to 73 years)
  • More common in women
Sites
  • More common in mandible than maxilla
    • 2/3 in mandible
Clinical features
  • Most patients are asymptomatic, usually incidental finding by imaging
  • Can present with swelling
Diagnosis
  • Diagnosis dependent on clinical, radiologic and pathologic correlation
Radiology description
  • Radiographically, appear as radiolucent lesions that can be uni or multilocular creating a soap bubble or honeycomb appearance
  • Cortical peforation can be seen
Radiology images

Images hosted on other servers:

Multilocular, radiolucent lesion

Right mandibular lateral occlusal view

Multilocular radiolucent osteolytic lesion

CT Scan of mandible

Prognostic factors
  • ~25% recurrence rate, usually after incomplete excision
Case reports
Treatment
  • Surgery is mainstay of treatment
  • Smaller lesions often treated with curettage
  • Larger lesions with complete excision
Clinical images

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Swelling on the right side

Mandibular right quadrant

Gross images

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Gray white appearance

Jelly-like appearance

Microscopic (histologic) description
  • Spindled to stellate cells with eosinophilic cytoplasm set in myxoid matrix
  • Binucleated heart shaped cells, mitoses and minimal atypia can be seen
  • If abundant collagen present, the term "myxofibroma" or "fibromyxoma" has been used
  • Occasional scattered epithelial rests can be seen
Microscopic (histologic) images

Images hosted on PathOut server:

Images contributed by Kelly Magliocca D.D.S., M.P.H.

H&E stain



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H&E

Spindle shaped cells with long cytoplasmic processes

H&E 100x

Positive stains
  • Orosomucoid 1 protein (ORM-1)
  • SMA
Negative stains
Molecular / cytogenetics description
  • Decreased immunostaining for the protein product and occasional mutations of the PRKAR1A gene have been identified (Genes Chromosomes Cancer 2005;44:204)
    • Likely represent sporadic mutations and not those seen in Carney complex (CNC)
  • Odontogenic myxomas do not appear to be associated with GNAS1 mutations like those seen in Mazabraud syndrome
Differential diagnosis
  • Based on histology of spindled cells with myxoid / fibromyxoid stroma
    • Dental papilla
      • Immature dental pulp from a developing tooth can be mistaken for a myxoma
      • Have a rim of odontoblasts / epithelium, myxomas do not have this
    • Chondromyxoid fibroma
      • Have stellate cells, but they tend to be more uniform and the lesion is often lobulated, and hypocellular centrally and hypercellular at the periphery
      • Often scattered giant cells at the periphery
      • Calcification and hyaline cartilage can be variably present
    • Odontogenic fibroma
      • Similar peak age of presentation
      • Can also have spindled cells but usually more cellular and fibrocollagenous with strands of odontogenic epithelium
        • Calcifications can be seen in the epithelium
    • Osteochondromyxoma
      • Usually present in a younger age group with the nasal cavity being the most common site
      • Can also have stellate cells in a myxoid stroma
      • Tend to grow in a lobulated pattern with cementoid hyaline bodies similar to unicameral bone cyst
      • Can show loss of PRKAR1A as the majority of the cases are associated with Carney complex
    • Based on radiology
Board review question #1
Odontogenic myxomas are known to be associated with which syndrome?

  1. Carney complex
  2. Mazabraud syndrome
  3. Both Mazabraud syndrome and Carney complex
  4. None of the above
Board review answer #1
D. None of the above