Intertrabecular vertebral metastases: metastases only detectable on MR imaging.

Metastatic intertrabecular vertebral tumors that infiltrate the marrow space without trabecular bone alteration are not visible on radiographs or bone scans. To understand the clinical importance of intertrabecular metastases, their histological and radiological aspects were reviewed based on an examination using 69 cadavers. Metastatic tumors were found in 940 of 1653 vertebral bodies. Radiography of the specimen demonstrated lesions in 485 of 940 vertebral bodies (51.6%). Bone scintigraphy showed lesions in 109 of 415 vertebral bodies (26.3%) with tumors examined within 3 months before autopsy, whereas magnetic resonance (MR) images detected 132 of 146 (90.4%) lesions. The intertrabecular metastases were found in 36.9% of the metastatic lesions and was difficult to see on radiography (5.8%) and bone scans (3.3%) whereas MR images detected most of them (94.6%). The intertrabecular metastasis is the most common type of skeletal metastases and is only detectable on MR images.