Introduction:
Despite a wide range of imaging modalities available today, clinically silent osteolytic changes in the skeletal system occurring in children are still a diagnostic challenge.

Case report:
The study presents the case of 10-year-old girl with a tumour in a thoracic vertebra. The patient was admitted to the Paediatric Orthopedics Clinic in the Paediatric Clinical Hospital in Lublin suffering from severe pain in the thoracic and lumbar spine. The pain had started suddenly. Physical examination showed lumbar spine pain and a forced scoliotic position. To reduce the symptoms, spinal traction, analgetics and myorelaxing drugs were used. X-ray and CT of the spine showed congenital unfused S1-S3 vertebrae. An MRI was scheduled for further diagnosis. After treatment, the symptoms disappeared and the the patient was discharged after 6 days. MRI showed an oval, well-demarcated lesion in the vertebra body and left side of the arch of the Th10 vertebra. The patient was admitted to the Clinic one again. CT scan of the thoracic spine showed an osteolytic lesion in Th10 vertebra. In the spine X-ray irregular vertebral body contour in Th10 vertebra, was seen. There were no signs of neoplastic infiltration. Scintigraphy showed increased radioisotope uptake in spinal processes of Th10 and Th11 vertebrae, which confirmed the MRI results. A transpendicular trepanobiopsy of the Th10 vertebrae was performed to provide material for histopathological examination. Then, a transpedicular stabilization of Th9-Th11 vertebrae and posterior sponylodesis with spinal autografts was performed. Histopathological examination showed no malignant cells but did not help to establish a diagnosis.

Conclusions:
In spite of using all the available diagnostic methods it was impossible to determine the type of lesion in the patient’s spine. Genetic tumour marker test can be considered.