Bone & joints
Other osteogenic tumors
Osteoma


Minor changes: 22 July 2021

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PubMed Search: Osteoma pathology [TI]

Serenella Serinelli, M.D., Ph.D.
Gustavo de la Roza, M.D.
Page views in 2020: 19,524
Page views in 2021 to date: 12,059
Cite this page: Serinelli S, de la Roza G. Osteoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/boneosteoma.html. Accessed July 24th, 2021.
Definition / general
  • Benign, bone forming tumor composed of mature cortical type or less frequently, trabecular bone, typically involving the craniofacial skeleton
Essential features
  • Benign osteogenic tumor
  • Usually involves the surface of craniofacial bones
  • Admixture of mature lamellar and woven bone patterns, with Haversian-like canals
  • Cortical type bone architecture is typical
  • Lack of cellular atypia
Terminology
  • Torus palatinus (if palate is involved)
  • Torus mandibularis (if mandible is involved)
  • Parosteal osteoma
  • Button osteoma
  • Ivory exostosis
ICD coding
  • ICD-O: 9180/0 - osteoma, NOS
  • ICD-11:
    • XH4818 - osteoma, NOS
    • 2E83.Z - benign osteogenic tumor of unspecified site
Epidemiology
  • Incidence:
    • Accounts for 0.03% of biopsied primary bone tumors
    • Paranasal sinus osteoma: 3 - 6.4% of CT scans performed for sinus conditions (Acta Otolaryngol 2015;135:602)
  • Age: fourth through sixth decades
  • Sex: M = F
Sites
Pathophysiology
  • Controversy in the literature whether osteoma represents a true neoplasm or a developmental anomaly
Etiology
  • Still unclear
  • Theories: reactive bone hyperplasia triggered by trauma or infection; advanced ossification; end stage of fibrous dysplasia or subperiosteal hematomas (Imaging Sci Dent 2011;41:107)
  • Presence of multiple osteomas is suggestive of Gardner syndrome, a variant of familial adenomatous polyposis (FAP) that is characterized by colorectal adenomas, osteomas and benign skin tumors; it is caused by mutations in the APC gene (Imaging Sci Dent 2016;46:267)
Clinical features
Diagnosis
  • Radiology findings often helpful
Radiology description
  • In general, the lesion involves the surface of the bone and appears well delineated, ovoid or mushroom shaped, with broad base of attachment to cortex (Nielson: Diagnostic Pathology - Bone, 2nd Edition, 2017)
  • Xray: radiodense lesion with varying amounts of central lucency
  • CT: cortical density on bone window; no contrast enhancement (Clin Radiol 2000;55:435)
  • MRI: low signal intensity on T1 and T2 weighted images; no contrast enhancement
Radiology images

AFIP images
Dense lobular mass in frontal sinus

Dense lobular mass in frontal sinus



Images hosted on other servers:
CT bone window

CT bone window

Prognostic factors
  • Excellent prognosis
  • No recurrence if completely excised
Case reports
Treatment
  • Observation for asymptomatic cases
  • Surgical excision for symptomatic cases
Clinical images

Images hosted on other servers:
Osteoma of anterior maxilla

Osteoma of anterior maxilla

Forehead osteomas

Forehead osteomas

Nasal cavity osteoma with actinomycosis

Nasal cavity osteoma with actinomycosis

Gross description
Gross images

Contributed by David R. Lucas, M.D. and Mark R. Wick, M.D.
Osteoblastoma-like osteoma Osteoblastoma-like osteoma

Osteoblastoma-like osteoma

Skull osteoma

Skull osteoma



Images hosted on other servers:
Osteoma with smooth bosselated surface

Osteoma with smooth bosselated surface

Giant orbit osteoma

Giant orbit osteoma

Fronto-ethmoidal osteoma

Fronto-ethmoidal osteoma

Microscopic (histologic) description
  • Admixture of mature lamellar and woven bone patterns, with Haversian-like canals, which may have various sizes and shapes (Nielson: Diagnostic Pathology - Bone, 2nd Edition, 2017)
  • More frequent: cortical type bone architecture
  • Less frequent: trabecular bone architecture
  • Osteoblasts rimming bone are inconspicuous and small but can be prominent in growing lesions
  • Osteocytes in the matrix are small, not atypical and randomly distributed (Surg Pathol Clin 2012;5:101)
  • Intertrabecular marrow spaces are filled with moderately cellular, loose fibrous stroma (BMJ Case Rep 2013;2013:bcr2013009857)
  • Inflammatory infiltrates are typically absent
Microscopic (histologic) images

Contributed by Serenella Serinelli, M.D., Ph.D. and Gustavo de la Roza, M.D.
Cortical type bone architecture

Cortical type bone architecture

Trabecular bone architecture

Trabecular bone architecture

Lamellar bone

Lamellar bone

Osteoblasts and osteocytes

Osteoblasts and osteocytes

Fibrous stroma in marrow spaces

Fibrous stroma in marrow spaces

Videos

Osteoma of bone

Sample pathology report
  • Bone, left forehead, excision:
    • Osteoma
Differential diagnosis
Board review style question #1

A 40 year old woman seeks treatment for a slowly enlarging lesion over the left forehead. The mass is found to involve the external surface of the left frontal skull and is excised. The histology is shown above. What is the diagnosis?

  1. Osteoblastoma
  2. Osteochondroma
  3. Osteoid osteoma
  4. Osteoma
  5. Parosteal osteosarcoma
Board review style answer #1
D. Osteoma

Comment Here

Reference: Osteoma
Board review style question #2
Which of the following is a feature of osteoma?

  1. Atypia has to be present to make the diagnosis
  2. Involves mainly the long bones
  3. Most frequent architecture is cortical type bone
  4. Most frequent architecture is trabecular bone
  5. Typically does not involve the craniofacial skeleton
Board review style answer #2
C. Most frequent architecture is cortical type bone

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Reference: Osteoma
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