Bone & joints
Other tumors
Adamantinoma

Resident / Fellow Advisory Board: Erna Forgó, M.D.
Borislav A. Alexiev, M.D.
William B. Laskin, M.D.

Minor changes: 9 March 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Adamantinoma [title] bone osteofibrous dysplasia-like

Borislav A. Alexiev, M.D.
William B. Laskin, M.D.
Page views in 2020: 6,262
Page views in 2021 to date: 2,228
Cite this page: Alexiev BA, Laskin WB. Adamantinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/boneadamantinoma.html. Accessed April 15th, 2021.
Definition / general
  • Rare malignant primary bone tumor of uncertain histogenesis characterized by epithelial structures embedded in a mesenchymal (osteofibrous dysplasia-like) stroma
Essential features
  • Primary biphasic fibro-osseous tumor of bone
  • Almost exclusively involves the tibia or fibula
  • 3 clinicopathologic variants:
    • Osteofibrous dysplasia (OFD)-like (differentiated) adamantinoma: inconspicuous clusters of epithelial cells embedded in fibro-osseous stroma
    • Classic adamantinoma: obvious epithelial elements embedded in fibro-osseous stroma
    • Dedifferentiated adamantinoma: loss of epithelial differentiation, sarcomatoid change
Terminology
  • Not recommended: well differentiated adamantinoma
ICD coding
  • ICD-O:
    • 9261/1 - osteofibrous dysplasia-like adamantinoma
    • 9261/3 - adamantinoma of long bones
  • ICD-11:
    • 2B5J & XH1SV4 - malignant miscellaneous tumors of bone or articular cartilage of other or unspecified sites and ameloblastoma, NOS
Epidemiology
Sites
Etiology
Clinical features
  • Initial symptoms are often indolent and nonspecific and depend on location and extent of the disease (Diagn Pathol 2008;3:8)
  • Onset is insidious and its course shows a slow, progressive character (Diagn Pathol 2008;3:8)
Diagnosis
  • Despite advances in imaging techniques, the definitive diagnosis is mainly established by histopathological examination (StatPearls: Adamantinoma [Accessed 18 January 2021])
  • Open biopsy is better to obtain additional samples
  • Any difficult or nondiagnostic biopsies of solitary bone lesions should be referred to subspecialty expert for a second opinion
Radiology description
  • Single or multiple variably sized lytic lesions with sclerotic borders (soap bubble appearance) involving the diaphyseal and less commonly, the metaphyseal cortex; multifocality within the bone and invasion of the medullary cavity or extraosseous soft tissue invasion may occur (best visualized with MRI) (J Surg Oncol 2020;122:273, Pediatr Radiol 2006;36:1068)
  • Computed tomography of the primary site elucidates the cortical involvement and is important for detection of metastases (J Surg Oncol 2020;122:273)
  • Osteofibrous dysplasia-like adamantinoma is strictly intracortical (like osteofibrous dysplasia)
Radiology images

Contributed by Borislav A. Alexiev, M.D.
Tibia lesion, radiography

Tibia lesion, radiography

Tibia lesion, MRI

Tibia lesion, MRI

Prognostic factors
Case reports
Treatment
  • Typically, adamantinomas are treated surgically with wide local resection; intralesional or marginal excision carries an increased risk of local recurrence (J Surg Oncol 2020;122:273)
  • Long term follow up is necessary due to the possibility of late complications
Gross description
  • Most often the tumor is yellow-gray or grayish white and fleshy or firm in consistency (Diagn Pathol 2008;3:8)
  • Occasionally, tumors show macroscopic cysts containing a straw colored or blood-like fluid on gross examination (Cancer 1974;34:1796)
Gross images

Contributed by Mark R. Wick, M.D.
Tibial lesion

Tibial lesion

Microscopic (histologic) description
  • Biphasic tumor characterized by epithelial and osteofibrous components that may be intermingled with each other in various proportions and differentiating patterns (Diagn Pathol 2008;3:8, J Bone Joint Surg Am 1994;76:1482, J Surg Oncol 2020;122:273)
  • Fibrous component may be loose myxoid, hyalinized or sclerotic (Cancer 1989;64:730)
  • Mitotic figures are usually infrequent, most reporting 0 - 2 mitoses per 10 high power fields (Cancer 1989;64:730, J Bone Joint Surg Am 1994;76:1482)
  • Morphologic variants:
    • Classic adamantinoma
      • Prominent epithelial component composed of mildly atypical epithelial cells within an osteofibrous dysplasia-like stroma forming conspicuous solid basaloid nests with peripheral palisading or less often, tubular structures, keratinized squamous nests or spindled cell bundles (Am J Surg Pathol 2013;37:710)
    • Osteofibrous dysplasia-like adamantinoma
      • Characterized by small scattered epithelial clusters highlighted with keratin immunostaining within a prominent osteofibrous dysplasia-like stroma (Head Neck Pathol 2015;9:32)
    • Dedifferentiated adamantinoma
      • Exhibits sarcomatoid features including mitotically active, highly pleomorphic cells and oftentimes, osteoid and chondroid deposition or clear cell change
      • Keratin immunostaining may be negative in sarcomatous areas (Am J Surg Pathol 2013;37:710)
Microscopic (histologic) images

Contributed by Borislav A. Alexiev, M.D. and William B. Laskin, M.D.
Fibro-osseous lesion

Fibro-osseous lesion

Trabecular growth pattern

Trabecular growth pattern

Anastomosing trabeculae of epithelial cells

Anastomosing trabeculae of epithelial cells

Anastomosing trabeculae of epithelial cells

Epithelial cells


Classic adamantinoma

Classic adamantinoma

Osteofibrous dysplasia-like adamantinoma

Osteofibrous dysplasia-like adamantinoma

AE1 / AE3 expression

CK AE1 / AE3 expression

CK19 expression

CK19 expression

Cytology description
  • Biphasic admixture of epithelioid cells and cells with prominent spindling seen singly and in fragments (Diagn Cytopathol 2010;38:198)
  • Epithelioid cells with indistinct cytoplasm, bland round to oval nuclei with finely dispersed chromatic, occasional micronucleoli and well formed nuclear grooves (Diagn Cytopathol 1994;10:347)
  • Other population has more elongated nuclei, ample clear cytoplasm and spindled appearance (Diagn Cytopathol 2010;38:198)
Electron microscopy description
  • Epithelioid tumor cells possess epithelial ultrastructural features including tonofilaments, hemidesmosomes and desmosomes (Clin Orthop Relat Res 1984:299)
Molecular / cytogenetics description
Sample pathology report
  • Left tibia, bone biopsy:
    • Adamantinoma, classic variant (see comment)
    • Comment: MRI demonstrates a T1 isointense, T2 hyperintense, mildly enhancing lobulated lesion in the left distal tibia, not significantly different in appearance or number from the prior exam. The neoplasm is composed of basaloid cells with eosinophilic cytoplasm arranged in cords and nests. Nuclei are monomorphic, ovoid or round, with minimal atypia. Interspersed between the cells there is abundant fibrous stroma. No mitotic figures are identified (0 mitoses/10 high power fields). The tumor cells are positive for keratin AE1 / AE3 and p63 and negative for CD99, CAM5.2 and ERG. The findings support the above diagnosis. Adamantinomas are considered malignant neoplasms that frequently recur locally and can rarely metastasize.
Differential diagnosis
Additional references
Board review style question #1

The most common gene rearranged in adamantinomas is

  1. KMT2D (MLL2)
  2. FUS
  3. SS18
  4. ZNF444
  5. FOS
Board review style answer #1
A. KMT2D (MLL2)

Comment Here

Reference: Adamantinoma
Board review style question #2
A 40 year old man presents with a left tibia mass. Radiography demonstrates a radiolucent lesion in mid / distal shaft with 2 satellite lesions proximally. Hematoxylin eosin stains show a nested and trabecular growth of basaloid and spindle cells with uniform, round to ovoid nuclei and eosinophilic or pale cytoplasm in fibrous background. Occasional mitotic figures are identified (1 mitosis/10 high power fields). Immunohistochemical stains for keratin AE1 / AE3, CK19 and vimentin are positive in tumor cells, while all of the following are negative: CAM5.2, MDM2, CD34, ERG, NKX2.2 and CD99.

Which of the following is most likely the correct diagnosis?

  1. Ewing sarcoma
  2. Low grade central osteosarcoma
  3. Metastatic carcinoma
  4. Pseudomyogenic hemangioendothelioma
  5. Adamantinoma
Board review style answer #2
E. Adamantinoma

Comment Here

Reference: Adamantinoma
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