Endometriosis presenting as a pre-sacral mass lesion causing sacral foraminal expansion and S1 radiculopathy.
DiscussionThe MR examination demonstrates a 6×2.5-cm pre-sacral mass lesion that is extending into and expanding the left S1 exit foramen. This mass extends into the epidural fat, displacing and partially surrounding the S1 nerve, but it did not extend distally to affect the exiting S2 or S3 nerves. The lesion shows a heterogeneous signal pattern on T1-and T2-weighted sequences with focal areas of high signal intensity on the T1-weighted sequences indicative of small areas of haemorrhage. The lesion is predominantly hyperintense to muscle on T2 weighting and following contrast medium administration, and a relatively uniform enhancement pattern is identified. Trans-sacral biopsy by an approach lateral to the exit foramen was performed to exclude recurrent rectal carcinoma. The biopsy material demonstrated endometriosis characterised by endometrial glands surrounded by endometrial stroma with strong positivity for oestrogen and progesterone. As a result, the patient was commenced on hormonal treatment and the neurological symptoms improved.