Adamantinoma - Pathology

summary
- Adamantinomas are rare, low-grade malignant tumors of unknown etiology that are almost always located in the diaphysis of the mid-tibia.
- The condition usually presents in patients who are between 20 and 40 years old with regional pain and a palpable mass.
- Diagnosis is made with a biopsy showing nests of epithelial-like cells arranged in palisading or glandular pattern, in a background of fibrous stroma.
- Treatment is usually wide-margin surgical resection.

Epidemiology
- Incidence
  - less than 300 cases have been documented
- Demographics
  - occurs in young adults (20 - 40 years of age)
- Anatomic location
  - almost always located in mid-tibia

Etiology
- Pathophysiology
  - unknown
- Associated conditions
  - osteofibrous dysplasia
    
    historically, it was thought that osteofibrous dysplasia (OFD) was a precursor to this adamantinoma, however current studies have cast doubt on this theory

Presentation
- Symptoms
  - pain of months to years duration
- Physical exam
  - bowing deformity or a palpable mass of tibia is common

Imaging
- Radiographs
  - multiple sharply circumscribed lucent lesions ("soap bubble" appearance) with interspersed sclerotic bone in mid-tibia
    
    some lesions may destroy cortex
  - may see bowing of the tibia
  - radiographic evolution of lesions is helpful in the diagnosis as lesions may continue to grow and erode thru the cortex
  - unlike other primary bone tumors, adamantinoma typically shows no periosteal reaction

Studies
- Histology
  - biphasic
  - contains both epithelial and fibrous mesenchymal cells
    
    nests of epithelial-like cells arranged in palisading or glandular pattern
    
    stain for keratin
    
    background of fibrous stroma

                        Differential
                    
                        Osteofibrous dysplasia
                    
                        differentiating between osteofibrous dysplasia and adamantinoma is critical
                    
                        osteofibrous dysplasia is benign and  treated with observation
                    
                        adamantinoma is malignant and treat with surgical resection
                    
                        Differential diagnosis of Adamantinoma
                    
                        Tibial diaphysis lesion
                    
                        Treated with wide-resection alone
                    
                        Adamantinoma
                    
                        o
                    
                        o
                    
                        Osteofibrous dysplasia
                    
                        o
                    
                        Chondrosarcoma
                    
                        o
                    
                        Parosteal osteosarcoma
                    
                        o

Treatment
- Operative
  - wide-margin surgical resection
    
    indications
    
    standard of care in most patients
    
    techniques
    
    often requires intercallary resection with allograft or intercallary megaprosthesis reconstruction
    
    as adamantinoma is a low-grade malignancy, radiotherapy and/or chemotherapy is not typically used for local control of disease

Prognosis
- May metastasize to lungs (25%), therefore long-term followup is recommended
- Recurrence is uncommon with negative margin excision

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T

Differential diagnosis of Adamantinoma
	Tibial diaphysis lesion	Treated with wide-resection alone
Adamantinoma	o	o
Osteofibrous dysplasia	o
Chondrosarcoma		o
Parosteal osteosarcoma		o