Mandible - Maxilla
Malignant tumors
Malignant ameloblastoma

Author: Kelly Magliocca, D.D.S., M.P.H. and Anthony Martinez, M.D. (see Authors page)

Revised: 10 May 2016, last major update May 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Malignant ameloblastoma

Cite this page: Malignant ameloblastoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillamalignantameloblastoma.html. Accessed December 7th, 2016.
Definition / General
  • Ameloblastomas that metastasize despite their benign histologic appearance
Terminology
  • Also called metastatizing ameloblastoma
Epidemiology
  • Represent < 1 - 2% of all ameloblastomas
  • Usually occur a decade after treatment for primary ameloblastoma (range < 1 to 45 years)
Sites
  • Most common site of metastasis is the lungs
    • ~ 75 - 88%
    • Rate does not differ by gender
    • Can follow multiple local recurrences
  • Cervical lymph nodes are second most common site
  • Other less common sites include vertebrae, pleura, skull, parotid gland, diaphragm and liver
Etiology
  • Metastases develop from angiolymphatic spread from primary tumors
  • A few metastases are hypothesized to have occurred secondary to aspiration
    • Theory supported by tumor that grew within the bronchi and bronchioli
    • This assumption is further supported because such tumors are often located in the right lung
Clinical Features
  • Clinically, symptoms of metastasis can be related to site or may be found incidentally with imaging after a local recurrence
  • For lung metastases, patients may exhibit cough, dyspnea and hemoptysis, rarely paraneoplastic syndrome (ecancer 2013;7:323)
  • Lymphadenopathy
Diagnosis
  • Based on clinical, radiologic and pathologic correlation
Radiology Description
  • On radiograph, primary lesion will have classic appearance as ameloblastoma, namely well defined unilocular or multilocular radiolucent lesion, often with cortical expansion
  • Appearance of metastatic lesion will vary depending on site
Radiology Images

Images hosted on other servers:

Cavitary lesion

Various imaging of pulmonary metastases

Prognostic Factors
  • Metastatic cases to lung tend to show indolent clinical behavior with long survival times
  • True long term followup is difficult to assess as many studies of malignant ameloblastomas also included ameloblastic carcinomas
Case Reports
Treatment
  • Surgical excision
  • Role of chemotherapy or radiation has yet to be defined; many case reports have seen clinical response with systemic therapy
Micro Description
  • Identical to ameloblastoma
    • Odontogenic epithelial islands composed of:
      • Peripheral palisading columnar
      • Ameloblastic cells with reverse polarization
      • Stellate reticulum - like cells composed of loosely arranged angular cells
  • Many subtypes
    • Follicular: most common subtype; islands of odontogenic epithelium in fibrous connective tissue; may be cystic
    • Acanthomatous: squamous metaplasia and variable keratinization of stellate reticulum-like cells
    • Plexiform: cords and sheets of anastomosing odontogenic epithelial cells
    • Granular cell: granular eosinophilic cytoplasm often located within stellate reticulum-like cells
    • Basaloid: least common variant; nest or islands of hyperchromatic basal cells without stellate reticulum-like
Micro Images

Images hosted on other servers:

Solid / multicystic type

Pulmonary metastasis

Acanthomatous

Various images

Differential Diagnosis
  • Ameloblastoma: histologically identical but no metastases
  • Ameloblastic carcinoma
    • Variable features of ameloblastoma: peripheral palisading, reverse polarization, stellate reticulum-like cells
    • Features of malignancy include cytological atypia, high N:C ratio, increased mitoses with atypical forms, necrosis
    • Can also metastasize
  • Ameloblastic fibroma
    • Histologically, may share same features within the odontogenic epithelial component strands, cords and islands that may exhibit peripheral palisading, reverse polarization and stellate reticulum-like cells
    • Stroma is more primitive, delicate and lobular in appearance
    • Should not metastasize
  • Metastatic disease in lung
    • Primary squamous cell carcinoma of lung
    • Has cytologic features of malignancy
    • No other features of ameloblastoma; i.e. no peripheral palisading, no polarization, no stellate reticulum -like cells