Simple Bone Cyst
Synonym / Acronym
Traumatic bone cyst, simple bone cavity, solitary bone cyst, hemorrhagic cyst, intraosseuous hematoma, idiopathic bone cyst, extravasation bone cyst.
Definition
Simple bone cyst is not classified as a true cyst because the lesion contains no fluid and it lacks an epithelial lining. It is found to be empty or filled with serous or sanguineous fluid. The etiology is unknown. The various names that have been associated with SBC are speculations as to the possible etiology of this lesion. No evidence exists to support a traumatic cause.
Clinical Features
Simple bone cyst is found mostly during the second decade of life. It is common to see SBC with cemento-osseuous dysplasia in older age population; usually around 42 years of age with female predilection 4:1. Simple bone cyst is usually painless lesion having no signs and symptoms unless it got secondarily infected. The involved teeth are vital. There might be swelling but that would unusual. Most SBCs are found as incidental findings during routine radiographic examination and that’s why they can become quite large.
Radiographic Features
SBC occur most of the time in the mandible with equal frequency in the body and ramus area. The margins can vary from smooth well-defined corticated to ill-defined. It is easier to identify the superior border of the lesion in the alveolar cortex than inferior border of the lesion. The lesion is oval resembling a cyst. It scallops between roots of involved teeth and causes sparring of the roots. Simple bone cyst is uniformly radiolucent and sometimes although it doesn’t have septa, it can look as a multilocular lesion. This look is due to the propensity of the lesion to scallop endosteal surface of the outer cortex of the mandible.
Differential Diagnosis
Simple bone cyst can look similar to KCOT as KCOT tends to grow along the bone without causing much expansion. However, KCOT have better defined outline and it may sometimes causes displacement and resorption of teeth. One can include a malignancy due to the lesion’s behavior to scallop around roots of teeth. However, since it preserves lamina dura and does not destroy bone, we can remove malignancy from our differential. A care should be taken regarding interpreting findings on a biopsy for SBC as it can be a healing cyst and mistakenly can indicate presence of ossifying fibroma or fibrous dysplasia due to formation of new immature bone. Thus the diagnostic replies primarily on radiographic and surgical observations.
Treatment
Curettage of the lesion’s lining to allow bleeding to happen and initiate subsequent healing.
Case Reports
HISTORY: A 47-year-old female patient was referred for a Cone Beam CT evaluation for #19 implant site assessment.
FINDINGS: A well-defined radiolucency is seen distal to tooth #19 and extends back to the retromolar region and inferiorly to the inferior border of the mandible. There is slight expansion. The lesion measures approximately 14 x 19 mm. There is involvement of the mandibular canal. The lesion appears to follow a torturous path. The lesions might be perforating the lingual cortical plate as indicated by an arrow.
IMPRESSION: Given the radiographic signs and patient history:
- Simple bone cyst
- Keratocystic odontogenic tumor
- Arteriovenous malformation
HISTORY: An 11-year-old female patient was referred for a Cone Beam CT evaluation of the anterior mandible. Intraorally, there was only mild tenderness to palpation.
FINDINGS: There is a well-defined radiolucent lesion in the anterior mandible. The lesion has partially sclerotic borders. There is slight buccal and lingual expansion in the area of teeth #21-26. There are no signs of roots resorption or displacement.
IMPRESSION: The differential diagnosis include:
- Keratocystic odontogenic tumor
- Central cell giant cell granuloma
- Aneurysmal bone cyst
- Simple bone cyst
HISTORY: An 11-year-old female patient was referred for a Cone Beam CT evaluation of a swelling in the left mandible. Swelling was first noted recently by the patient and her mother.
FINDINGS: There is a well-defined radiolucency associated with teeth #17-19. The lesion measure approx. 3 cm x 1.5 cm. The lesion involves the furcation are of the teeth. There is slight expansion and thinning of the buccal cortical border. There are no signs of root resorption or displacement.
IMPRESSION: The following differential diagnosis can be made:
- Keratocystic odontogenic tumor
- Simple bone cyst
- Central giant cell granuloma
Biopsy is recommended.
HISTORY: A 14-year-old male patient was referred for a Cone Beam CT evaluation of a radiolucent area in his left mandible.
FINDINGS: There is a well-defined and partially corticated radiolucency in the posterior left mandible. The lesion arises at the buccal aspect of #19 and extends to the apex of #18 apically, coronally, and distally. The lesion dimensions approximately are 25 mm x 14 mm x 12 mm. There are no signs of roots resorption.
IMPRESSION: The radiographic characteristics of the lesion are most consistent with an odontogenic cyst. Radicular cyst appears unlikely; therefore KCOT would be at the head of the differential list. A bengin odontogenic tumor such as mural ameloblastoma is a less likely possibility.
SURGEON REPORT: On evaluation, the patient has a radiolucent lesion in the area of teeth #18 and #19 which extends to the inferior border. There is sclerotic border of the area. The patient has a low bony trabecular pattern. Unable to palpate significant expansion. There was no odontogenic sensitivity. Differential diagnosis including simple bone cyst, aneurysmal bone cyst, and odontogenic lesion. Biopsy recommended to rule out odontogenic and vascular pathology.
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