A 45-year-old woman presented with a 3-year history of intermittent episodes of low back pain associated with left-sided sciatica. This had progressed over the past 18 months and the pain was now radiating to her toes, causing difficulty with walking. Clinical examination was normal and initial investigations including routine blood tests and radiographs of the lumbosacral spine were unremarkable. Her past medical history included rectal carcinoma, previous hysterectomy and bilateral oophorectomy, asthma and hyperthyroidism. MRI of the lumbar spine (not shown) and sacrum was performed including sagittal T1-weighted (Fig. 1a), sagittal T2-weighted (Fig. 1b), axial T2-weighted (Fig. 1c), axial fat-suppressed T1-weighted images pre- and post-gadolinium administration (Fig. 1d, e). A trans-sacral CT-guided biopsy was performed, the histology of which is illustrated in Fig. 2.

Fig. 1
figure 1

MRI of the sacrum (arrows) included a sagittal T1-weighted, b sagittal T2-weighted, c axial T2-weighted, d, e axial fat-suppressed T1-weighted images pre- (d) and post-gadolinium (e) administration

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Fig. 2
figure 2

Histopathology image of the CT-guided biopsy material (H&E)

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