JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
SEPTEMBER 2018
D-N02

SIGNALMENT (JPC# 2979264):  Rhesus macaque

HISTORY:  None

HISTOPATHOLOGIC DESCRIPTION:  Mandibular gingiva; alveolar bone; tooth: Expanding up to 90% of the submucosal connective tissue and compressing/replacing alveolar bone is a poorly demarcated, unencapsulated neoplasm composed of islands,cords and trabeculae of odontogenic epithelium attempting to recapitulate teeth on a moderate fibrovascular stroma. Peripheral  neoplastic cells are characterized by a prominent layer of tightly packed columnar cells with apically-located oval nuclei and prominent basilar cytoplasmic clearing (ameloblasts) which palisade along the basement membrane and occasionally surround few foci of loosely arranged stellate to fusiform cells with prominent intracellular bridging (stellate reticulum). Ameloblasts have distinct cell borders, moderate amounts of pale eosinophilic cytoplasm, a pale oval to elongate nucleus with finely stippled chromatin and 1-2 distinct nucleoli. The mitotic rate averages 1-5 per high power field, and there is multifocal single cell necrosis.  Along the basilar aspects of the palisading ameloblasts are streams of  variably thick, wedge-shaped homogeneous, brightly eosinophilic, extracellular matrix (atubular dentin), often directly adjacent to foci of fusiform to spindle cells that may be seen embedded in the matrix material in low numbers (odontoblasts).   Rarely the stroma adjacent to neoplastic epithelial cells contains aggregates of loosely arranged, primitive mesenchyme resembling the dental pulp.  Neoplastic trabeculae multifocally contain cystic areas (up to 3mm) filled with eosinophilic, granular fluid admixed with cellular debris and scattered degenerating neutrophils or macrophages. There is multifocal ulceration of the oral epithelium with replacement by numerous viable and degenerate neutrophils, macrophages and fewer lymphocytes admixed with necrotic bone fragments, cellular and karyorrhectic debris, basophilic granular mineral, plant material and numerous colonies of cocci. Neoplastic cells surround and compress foci of immature woven bone (pre-existing alveolar bone) with scalloped margins lined by few osteoblasts as well as osteoclasts in Howship’s lacunae (remodeling).  There are rare fragments of necrotic/lytic bone.

Tongue: Within normal limits.

MORPHOLOGIC DIAGNOSIS:  Gingiva; alveolar bone; tooth: Odontoameloblastoma, rhesus macaque (Macaca mulatta), nonhuman primate.

SYNONYMS:  Previously incorporated with ameloblastic odontoma (a term no longer recommended)

GENERAL DISCUSSION:

 PATHOGENESIS:

TYPICAL GROSS FINDINGS:

 TYPICAL MICROSCOPIC FINDINGS:

DIFFERENTIAL DIAGNOSIS:

Tumor

Odontogenic epithelium

Stroma

Mesenchyme

Matrix

Species affected

Misc

Odontoameloblastoma

Yes

Variable

Small amounts of ectomesenchyme may be present

Dentin in close relationship with odontogenic epithelium

+/- enamel

Horses, dog, llamas, rats, macaques, sheep, ox, guinea pig

Chords of odontogenic epithelium around dental matrix

Ameloblastoma

Yes

Not essential for diagnosis

None

None

Dog, cat, horse

Keratinization may occur

Amyloid producing

odontogenic

tumor

Yes

Not essential for diagnosis

None

Amyloid

Dog, cat, horse

Matrix composed of enamel proteins which are still Congophilic and exhibit apple-green birefringence; IHC + for laminin

Canine

acanthomatous

ameloblastoma

Yes

Stellate fibroblasts in

dense collagen;

regularly spaced

dilated, empty blood

vessels

Periodontal

ligament

None

Dog

Interconnected

sheets of

odontogenic

epithelium

 

Ameloblastic

fibroma

Yes (amount variable)

Loose, collagen poor,

resembles dental pulp

Dental pulp (abundant pulp stroma / ectomesenchyme)

None

Young

animals,

cattle

 

Most common

oral neoplasm

in cattle

 

Ameloblastic

fibro-odontoma

Yes (amount variable)

Loose, collagen poor,

resembles dental pulp

Dental pulp (abundant pulp stroma / ectomesenchyme)

 

Dentin or

Enamel; unorganized

 

Young

animals,

cattle

 

Complex

odontoma

Yes (amount variable)

Well-differentiated

dentinal tissue

Dental pulp variable

Dentin,

enamel (may

be mineralized); unorganized denticles

Dog, rodent,

primates,

horse

Horse, rodents

produce

cementum;

“balls of

disorganized

dental hard

substance”

Compound

odontoma

Yes (amount variable)

Well-differentiated

dentinal tissue; dense

collagen and vascular

connective tissue

Dental pulp variable

Dentin,

mineralized

enamel; organized denticles

Young dogs

Multiple

tooth-like

structures

(denticles)

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Andrews C, Gadsden BJ, Carr EA, Kiupel M. Pathology in practice: Compound odontoma in a horse. J Am Vet Med Assoc. 2014: 244(4):417-419.
  2. Bell CM, Soukup JW. Nomenclature and classification of Odontogenic Tumors – Part II: Classification of Specific Nomenclature. Journ Vet Dent. 2014;31:234-243.
  3. Burrough ER, Myers RK, Whitley EM. Spontaneous odontoameloblastoma in a female Sprague Dawley rat.  J Vet Diagn Invest. 2010;22:998-1001.
  4. Delaney MA, Singh K, Murphy CL, Solomon A, Nel S, Boy SC. Immunohistochemical and biochemical evidence of ameloblastic origin of feline amyloid-producing odontogenic tumors in cats. Vet Pathol. 2013;50(2):238-242.
  5. Miles CR, Bell CM, Pinkerton ME, Soukup JW. Maxillary ameloblastic fibroma in a dog.  Vet Pathol.  2011:48(4):823-826.
  6. Munday JS, Lohr CV, Kiupel M. Tumors of the Alimentary Tract. In: Meuten DJ, ed. Tumors in Domestic Animals. 5th ed. Ames, IA: John Wiley & Sons, Inc; 2017:530-543.
  7. Murphy B, Bell C, Koehne A, Dubielzig RR. Mandibular odontoameloblastoma in a rat and a horse. J Vet Diagn Invest. 2017: 29(4):536-540.
  8. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:22-25.
  9. Vorbach BS, Wolf JC, Yanong RP. Odontomas in two long-finned ocellaris clownfish (Amphiprion ocellaris). J Vet Diagn Invest. 2018: 30(1):136-139.
  10. Wong HE, Hedley J, Stapleton N, Murphy B, Priestnall SL. Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig. J Vet Diagn Invest. 2018: 30(5):793-797.


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