[Calcifying solitary bone cyst of the sacrum--A rare type of bone cyst and its unknown localisation, differential diagnosis and management].

AIM: The diagnostic procedures and management of calcifying bone lesions occurring in the sacrum.

METHOD: A case report of a rare type of bone cyst at an unknown localisation including the differential diagnosis and management.

RESULTS

Low back pain of a 41-year-old women was correlated with a calcifying bone formation of the sacrum on X-ray, demonstrating cystic, solid and exophytic components. On radionuclide bone scan, additional skeletal lesions were ruled out, the focus showed an increased uptake. An inflammatory process was excluded by lab studies. On computed tomography and magnetic resonance imaging, the calcifying bone formation was identified as surrounding the sacral canal, respecting the anatomical borders. Considering this anatomic region, a neurogenic tumor could be eliminated by the absence of neurological disorders, but the radiologic feature of this osseogenic process was not clear enough for classification. Hence, an incisional biopsy was essentially required. Describing the lesion as a bony cavity, the operating surgeon could macroscopically exclude an chordom a (known to be soft consistency). The histological work-up classified this tumor-like lesion as a calcifying solitary bone cyst (CSBC). A dorsal exostosis causing the complaint of the patient was resected. The patient became asymptomatic.

CONCLUSION

For the first time, a calcifying solitary bone cyst located in the sacrum is described, By sole resection of a dorsal exostosis causing the complaint, an overtreatment of grave consequences was avoided.