[Is CT-guided biopsy of aggressive sacral tumors always able to reach a diagnosis?]

To present a series of eight cases of rare sacral tumors that represent a wide spectrum of the aggressive disease involving the sacrum and to discuss the efficacy of CT-guided biopsy in these cases.

We reviewed all cases of sacral tumors biopsied under CT guidance in the last two years. Prior CT and MR images were analyzed before biopsy, and 3 mm CT slices of the lesion were obtained to determine the location of the target area and the path of the needle. All biopsies were performed using 11 G needles and 15 G coaxial needles.

Eight sacral lesions were biopsied under CT guidance, and a diagnosis was reached in four. In three of these, the diagnosis (chordoma, plasmocytoma, and metastasis from melanoma) was reached in a single session. In the fourth case, three sessions were necessary to reach the diagnosis of Ewing's sarcoma. For various reasons, the remaining four cases required surgical biopsy to reach the diagnoses of chondrosarcoma, eosinophilic granuloma, and primary bone lymphoma in two patients. The diagnostic efficacy of CT-guided biopsy was 36%.

Our results suggest that CT-guided biopsy is less useful in the characterization of primary tumors than in metastases. The diagnosis of primary bone lymphomas is especially complicated. Repeating the procedure after inconclusive results probably will not provide additional information, and it is recommendable to perform surgical biopsy in these cases.